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** Programmer's Technical Reference for MSDOS and the IBM PC ** USA copyright TXG 392-616 ALL RIGHTS RESERVED ───────────────────────────────┤ DOSREF (tm) ├──────────────────────────────── ISBN 1-878830-02-3 (disk-based text) Copyright (c) 1987, 1991 Dave Williams ┌─────────────────────────────┐ │ Shareware Version, 09/05/91 │ │ Please Register Your Copy │ └─────────────────────────────┘ C H A P T E R T H R E E THE PC ROM BIOS C O N T E N T S Calling the ROM BIOS .................................................. 3**1 Interrupt 10h Video Services ......................................... 3**2 Interrupt 11h Equipment Check ........................................ 3**3 Interrupt 12h Memory Size ............................................ 3**4 Interrupt 13h Disk Functions ......................................... 3**5 Interrupt 14h Initialize and Access Serial Port ...................... 3**6 FOSSIL Drivers ......................................... 3**7 Interrupt 15h Cassette I/O ........................................... 3**8 Interrupt 16h Keyboard I/O ........................................... 3**9 Interrupt 17h Printer ................................................ 3**10 Interrupt 18h ROM BASIC .............................................. 3**11 Interrupt 19h Bootstrap Loader ....................................... 3**12 Interrupt 1Ah Time of Day ............................................ 3**13 Interrupt 1Bh Control-Break .......................................... 3**14 Interrupt 1Ch Timer Tick ............................................. 3**15 Interrupt 1Dh Vector of Video Initialization Parameters .............. 3**16 Interrupt 1Eh Vector of Diskette Controller Parameters ............... 3**17 Interrupt 1Fh Ptr to Graphics Character Extensions (Graphics Set 2) .. 3**18 The ROM BIOS is the lowest level of software access. It contains the following routines: (all) power-on self-test (POST) boostrap loader clock floppy disk I/O video I/O keyboard serial ports parallel ports print screen equipment check report memory size (AT) hard disk I/O report memory size (extended memory) extended memory block moves enhanced video and keyboard I/O high resolution timer alarm Machines such as the PC Convertible, PCjr, and non-IBM machines add additional functions. Calling the ROM BIOS .................................................. 3**1 The BIOS services are invoked by placing the number of the desired function in register AH, subfunction in AL, setting the other registers to any specific requirements of the function, and invoking any of ints 10h through int 1Fh. The original IBM PC Technical Reference gave the absolute addresses of the ROM routines. Some early software jumped directly to these addresses, with mixed results on non-IBM BIOSes. This practice was common on machines predating the PC, but there is no practical use for it now. The OS/2 Compatibility Box also does not support jumping directly into the ROM. When the interrupt is called, all register and flag values are pushed into the stack. The interrupt address contains a pointer into an absolute address in the ROM BIOS chip address space. This location may be further vectored into the IBMBIO.COM (or equivalent) file or user file. The address vector points to a particular BIOS command handler. The handler pops the register values, compares them to its list of functions, and executes the function if valid. When the function is complete, it may pass values back to the command handler. The handler will push the values into the stack and then return control to the calling program. Most functions will return an error code; some return more information. Details are contained in the listings for the individual functions. Register settings listed are the ones used by the BIOS. Some functions will return with garbage values in unused registers. Do not test for values in unspecified registers; your program may exhibit odd behavior. Three sets of BIOS routines are available: PC BIOS, AT BIOS (also called CBIOS or "Old compatibility BIOS", and the PS/2 ABIOS "Advanced BIOS". The Advanced BIOS is contained in PS/2 ROMs. It is primarily intended for OS use rather than application use. OS/2 can take advantage of ABIOS routines to reduce RAM use on PS/2 systems. The ABIOS can be replaced by disk and RAM based ABIOS code if desired. There is a new BIOS Data Area defined in high memory that occupies one K of RAM. In OS/2 systems, parts of the ABIOS are replaced by OS/2 drivers. While the CBIOS must be addressed via pointers, the routines in the ABIOS are fixed in absolute locations so they can be referenced directly by OS/2. The ABIOS can run in protected mode, and is fully reentrant. It supports three types of function requests - single staged, discrete multistaged, or continuous multistaged. A single-staged request does its job immediately and returns control to the caller. A discrete multistaged request may happen in two or more stages with pauses between the stages. The caller may regain control during the pauses. A continuous multistaged request starts a staged operation that never ends. (sometimes called a daemon). Unlike the CBIOS which is called with software interrupts, ABIOS is accessed with FAR calls. ABIOS calls are completely reentrant in both real and protected modes. To call an ABIOS function, the calling program must pass pointers to two data structures - a request block and a common data area. The request block specifies the desired function number and the common data area is a table that contains pointers to all the ABIOS' other tables and data areas. The common data area's internal structure contains the function transfer tables which have the addresses of the BIOS routines. ABIOS stack frame and calling conventions: bytes stack contents 2 common data area pointer (segment/selector only) required 4 request block pointer - required 4 function transfer table pointer - furnished by ABIOS or caller 4 device block pointer - furnished by ABIOS or caller 4 return address In ABIOS Transfer Convention, only the first two items are required. ABIOS assigns the second two. In Operating System Transfer Convention, the caller provides the second two. Since the parameters are not removed from the stack on return to the caller, the operating system may save the function transfer table and device addresses after they have been furnished by the ABIOS by a call. ABIOS does no interrupt arbitration. It assumes all interrupts are handled by the caller or the OS and it is called only for service. If more than one device is sharing a hardware interrupt, the OS must determine which interrupt is valid for the ABIOS. OS/2 may use the ABIOS if found, but otherwise duplicates the BIOS calls for the DOS Compatibility Box by vectoring BIOS calls into its own device drivers. This makes it rather difficult for DOS drivers for mass storage, high resolution video boards, multitasking APIs using int 15h, etc. If your software needs to manipulate hardware directly you might want to check if your code is running under OS/2. The simplest method is to check for DOS version 10 or higher. note Some references list an "XT/2" machine, which was reputedly an 8mHz 8088 with 640k and a clock on the motherboard. IBM doesn't list such a machine, and I have a late '86 XT, one of the last made. It is pretty much like the older ones. ┌─────────────────────────────────────────────────────────────────────────────┐ │Interrupt 10h Video Services 3**2 │ └─────────────────────────────────────────────────────────────────────────────┘ (0:0040h) The BIOS Video Services may be found in Chapter 16. (internal) Coprocessor Error (80286+) Generated by the CPU when the -ERROR pin is asserted by the coprocessor (usually 80x87, but may be any multimaster CPU or alternate NDP such as Weitek, etc.). ATs and clones usually wire the coprocessor to use IRQ13, but not all get it right. ┌─────────────────────────────────────────────────────────────────────────────┐ │Interrupt 11h Equipment Check 3**3 │ └─────────────────────────────────────────────────────────────────────────────┘ (0:0044h) Reads the BIOS Data Area and returns two bytes of setup info. entry no parameters are required return AX Equipment listing word. Bits are: 0 number of floppy drives 0 no drives 1 bootable (IPL) diskette drive installed 1 math chip 0 no math coprocessor (80x87) present 1 math coprocessor (80x87) present (PS/2) 2 0 mouse not installed 1 mouse installed (PC) 2,3 system board RAM 0,0 16k (PC-0, PC-1) 0,1 32k 1,0 48k 1,1 64k (PC-2, XT) note 1) not commonly used. Set both bits to 1 2) both bits always 1 in AT 4,5 initial video mode 0,0 no video installed (use with dumb terminal) 0,1 40x25 color (CGA) 1,0 80x25 color (CGA, EGA, PGA, MCGA, VGA) 1,1 80x25 monochrome (MDA or Hercules, most super- hires mono systems) 6,7 number of diskette drives (only if bit 0 is 1) 0,0 1 drives 0,1 2 drives 1,0 3 drives 1,1 4 drives 8 0 DMA present 1 no DMA (PCjr, some Tandy 1000s, 1400LT) 9,A,B number of RS232 serial ports (0-3) 0,0,0 none 0,0,1 1 0,1,0 2 0,1,1 3 1,0,0 4 C 0 no game I/O attached 1 game I/O attached (default for PCjr) D serial accessory installation 0 no serial accessories installed 1 Convertible - internal modem installed or PCjr - serial printer attached E,F number of parallel printers 0,0 none 0,1 one (LPT1, PRN) 1,0 two (LPT2) 1,1 three (LPT3) note Models before PS/2 would allow a fourth parallel printer. Remapping of the BIOS in the PS/2s does not allow the use of LPT4. (386 extended AX) 23d 0 Weitek ABACUS - virtual '86 EMS page tables not correctly initialized 1 Weitek ABACUS - virtual '86 EMS page tables OK 24d 0 Weitek ABACUS NDP not present 1 Weitek ABACUS NDP present ┌─────────────────────────────────────────────────────────────────────────────┐ │Interrupt 12h Memory Size 3**4 │ └─────────────────────────────────────────────────────────────────────────────┘ (0:0048h) get system memory entry no parameters required return AX number of contiguous 1K RAM blocks available for DOS note 1) This is the same value stored in absolute address 04:13h. 2) For some early PC models, the amount of memory returned by this call is determined by the settings of the dip switches on the motherboard and may not reflect all the memory that is physically present. 3) For the PC/AT, the value returned is the amount of functional memory found during the power-on self-test, regardless of the memory size configuration information stored in CMOS RAM. 4) The value returned does not reflect any extended memory (above the 1 Mb boundary) that may be present on 80286 or 80386 machines. ┌─────────────────────────────────────────────────────────────────────────────┐ │Interrupt 13h Disk Functions 3**5 │ └─────────────────────────────────────────────────────────────────────────────┘ (0:0049h) The service calls for BIOS disk functions are located in Chapter 8. ┌─────────────────────────────────────────────────────────────────────────────┐ │Interrupt 14h Initialize and Access Serial Port For Int 14 3**6 │ └─────────────────────────────────────────────────────────────────────────────┘ Note: Some IBM PS/2 Model 50Z machines were delivered with serial ports that did not meet specification. Some cheap clone serial ports may also be troublesome. (0:0050h) the following status is defined: serial status byte: bits 0 delta clear to send 1 delta data set ready 2 trailing edge ring detector 3 delta receive line signal detect 4 clear to send 5 data set ready 6 ring indicator 7 receive line signal detect line status byte: bits 0 data ready 1 overrun error 2 parity error 3 framing error 4 break detect 5 transmit holding register empty 6 transmit shift register empty 7 time out note: if bit 7 set then other bits are invalid Though present on the IBM PS/2s, COM3 and COM4 are not widely standardized across the industry. The most common definitions are: port addr. IRQ interrupt COM1 3F8 IRQ4 int 0Ch COM2 2F8 IRQ3 int 0Bh COM3 3E8 IRQ4 int 0Ch COM4 2E8 IRQ3 int 0Bh As you can see, COM1/COM3 and COM2/COM4 are siamesed. Since the ISA bus does not support shared interrupts, simultaneous access of two of a pair may cause conflict. For example, a mouse and a modem would not coexist well on paired ports. All routines have AH=function number and DX=RS232 card number (0 based). AL=character to send or received character on exit, unless otherwise noted. entry AH 00h Initialize And Access Serial Communications Port bit pattern: BBBPPSLL BBB = baud rate: 110,150,300,600,1200,2400,4800,9600 PP = parity: 01 = odd, 11 = even S = stop bits: 0 = 1, 1 = 2 LL = word length: 10 = 7-bits, 11 = 8-bits AL parms for initialization: bit pattern: 0 word length 1 word length 2 stop bits 3 parity 4 parity 5 baud rate 6 baud rate 7 baud rate word length 10 7 bits 11 8 bits stop bits 0 1 stop bit 1 2 stop bits parity 00 none 01 odd 11 even baud rate 000 110 baud 001 150 baud 010 300 baud 011 600 baud 100 1200 baud 101 2400 baud 110 4800 baud 111 9600 baud (4800 on PCjr) DX port number (0=COM1, 1=COM2, etc.) return AH line status AL modem status note To initialize the serial port to > 9600 baud on PS/2 machines, see fns 04h and 05h. Function 01h Send Character in AL to Comm Port entry AH 01h AL character DX port number (0 - 3) return AH RS232 status code bit 0 data ready 1 overrun error 2 parity error 3 framing error 4 break detected 5 transmission buffer register empty 6 transmission shift register empty 7 timeout AL modem status bit 0 delta clear-to-send 1 delta data-set-ready 2 trailing edge ring detected 3 change, receive line signal detected 4 clear-to-send 5 data-set-ready 6 ring received 7 receive line signal detected Function 02h Wait For A Character From Comm Port DX entry AH 02h DX port number (0-3) return AL character received AH error code (see above)(00h for no error) Function 03h Fetch the Status of Comm Port DX (0 or 1) entry AH 03h DX port (0-3) return AH set bits (01h) indicate comm-line status bit 7 timeout bit 6 empty transmit shift register bit 5 empty transmit holding register bit 4 break detected ("long-space") bit 3 framing error bit 2 parity error bit 1 overrun error bit 0 data ready AL set bits indicate modem status bit 7 received line signal detect bit 6 ring indicator bit 5 data set ready bit 4 clear to send bit 3 delta receive line signal detect bit 2 trailing edge ring detector bit 1 delta data set ready bit 0 delta clear to send Function 04h Extended Initialize (Convertible, PS/2) entry AH 04h AL break status 01h if break 00h if no break BH parity 00h no parity 01h odd parity 02h even parity 03h stick parity odd 04h stick parity even BL number of stop bits 00h one stop bit 01h 2 stop bits (1½ if 5 bit word length) CH word length 00h 5 bits 01h 6 bits 02h 7 bits 03h 8 bits CL baud rate 00h 110 01h 150 02h 300 03h 600 04h 1200 05h 2400 06h 4800 07h 9600 08h 19200 DX comm port (0-3) return AH line control status AL modem status note Provides a superset of fn 00h capabilities for PS/2 machines. Function 05h Extended Communication Port Control (Convertible, PS/2) entry AH 05h AL 00h read modem control register 01h write modem control register BL modem control register bits 0 DTR data terminal ready 1 RTS request to send 2 out1 3 out2 4 loop 5,6,7 reserved DX port number (0=COM1, 1=COM2, etc.) return AH port status (see 00h above) AL modem status (see 00h above) BL modem control register (see 01h above) FOSSIL Drivers ........................................................ 3**7 Interrupt 14h FOSSIL (Fido/Opus/Seadog Standard Interface Level) drivers A FOSSIL is a device driver for handling the IBM PC serial communications ports in a standard fashion from an application (communications) program. A FOSSIL chains into the int 14h BIOS communications vector and replaces many functions with enhanced routines that may be easily accessed by an application. For all functions, all registers not specifically containing a function return value must be preserved across the call. entry AH 00h Set baud rate and parameters AL byte bits 7,6,5 baudrate 000 19200 baud 001 38400 baud 010 300 baud 011 600 baud 100 1200 baud 101 2400 baud 110 4800 baud 111 9600 baud bits 4,3 parity 00 none 01 odd 10 none 11 even bit 2 stop bits 0 1 stop bit 1 2 stop bits bit 1 char length 0 5 bits plus value other optional DX port number (NOP if DX=00FFh) return AX status (see fn 03h) note Low-order 5 bits are undefined by FOSSIL 1.0 spec. entry AH 01h Transmit character with wait AL ASCII value of character to be sent DX port number (NOP if DX=00FFh) return AX status bits (see function 03h) note 1) Character is queued for transmission. If there is room in the transmitter buffer when this call is made, the character will be stored and control returned to caller. If the buffer is full, the driver will wait for room. Use this function with caution when flow control is enabled. entry AH 02h FOSSIL: Receive a character with wait DX port number (0-3) (NOP if DX=00FFh) return AH RS-232 status code (see AH=00h above) AL ASCII value of character received from serial port note Will timeout if DSR is not asserted, even if function 03h returns data ready. entry AH 03h FOSSIL: Request status DX port number (NOP if DX=00FFh) return AX status bit mask AH bit 0 set RDA input data is available in buffer 1 set OVRN input buffer overrun 2 N/A 3 N/A 4 N/A 5 set THRE room is available in output buffer 6 set TSRE output buffer is empty 7 N/A AL bit 0 N/A 1 N/A 2 N/A 3 set this bit is always set 4 N/A 5 N/A 6 N/A 7 set DCD carrier detect note Bit 3 of AL is always returned set to enable programs to use it as a carrier detect bit on hardwired (null modem) links. entry AH 04h Initialize FOSSIL driver BX 4F50h (optional) DX port number (DX=00FFh special) ES:CX pointer to ^C flag address (optional) return AX 1954h if successful BL maximum function number supported (excluding 7Eh-0BFh) BH revision of FOSSIL supported note 1) DTR is raised when FOSSIL inits. 2) Existing baudrate is preserved. 3) If BX contains 4F50h, the address specified in ES:CX is that of a ^C flag byte in the application program, to be incremented when ^C is detected in the keyboard service routines. This is an optional service and only need be supported on machines where the keyboard service can't (or won't) perform an int 1Bh or int 23h when a control-C is entered. entry AH 05h Deinitialize FOSSIL driver DX port number (DX=00FFh special) return none note 1) DTR is not affected. 2) Disengages driver from comm port. Should be done when operations on the port are complete. 3) If DX=00FFh, the initialization that was performed when FOSSIL function 04h with DX=00FFh should be undone. entry AH 06h FOSSIL: Raise/lower DTR AL DTR state to be set 00h lower DTR 01h raise DTR DX comm port (NOP if DX=00FFh) return none entry AH 07h FOSSIL: Return timer tick parameters return AH ticks per second on interrupt number shown in AL AL timer tick interrupt number (not vector!) DX milliseconds per tick (approximate) entry AH 08h FOSSIL: Flush output buffer DX port number (NOP if DX=00FFh) return none note Waits until all output is done. entry AH 09h FOSSIL: Purge output buffer DX port number (NOP if DX=00FFh) return none note Returns to caller immediately. entry AH 0Ah FOSSIL: Purge input buffer DX port number (NOP if DX=00FFh) return none note 1) If any flow control restraint has been employed (dropping RTS or transmitting XOFF) the port will be "released" by doing the reverse, raising RTS or sending XON. 2) Returns to caller immediately. entry AH 0Bh FOSSIL: Transmit no wait AL ASCII character value to be sent DX port number (NOP if DX=00FFh) return AX 0000h character not accepted 0001h character accepted note This is exactly the same as the "regular" transmit call except that if there is no space available in the output buffer a value of zero is returned in AX, if room is available a value 1 (one) is returned. entry AH 0Ch FOSSIL: Nondestructive Read no Wait DX port number (NOP if DX=00FFh) return AH character 0FFFFh character not available note 1) Reads async buffer. 2) Does not remove keycode from buffer. entry AH 0Dh FOSSIL: Keyboard read no wait return AX IBM keyboard scan code or 0FFFFh if no keyboard character available note 1) Use IBM-style function key mapping in the high order byte. 2) Scan codes for non function keys are not specifically required but may be included. 3) Does not remove keycode from buffer. entry AH 0Eh FOSSIL: Keyboard input with wait return AX IBM keyboard scan code note Returns the next character from the keyboard or waits if no character is available. entry AH 0Fh Enable or Disable flow control AL bit mask describing requested flow control bits 0 XON/XOFF on transmit (watch for XOFF while sending) 1 CTS/RTS (CTS on transmit/RTS on receive) 2 reserved 3 XON/XOFF on receive (send XOFF when buffer near full) 4-7 not used, FOSSIL spec calls for setting to 1 DX port number (NOP if DX=00FFh) return none note 1) Bit 2 is reserved for DSR/DTR, but is not currently supported in any implementation. 2) TRANSMIT flow control allows the other end to restrain the transmitter when you are overrunning it. RECEIVE flow control tells the FOSSIL to attempt to do just that if it is being overwhelmed. 3) Enabling transmit Xon/Xoff will cause the FOSSIL to stop transmitting upon receiving an Xoff. The FOSSIL will resume transmitting when an Xon is received. 4) Enabling CTS/RTS will cause the FOSSIL to cease transmitting when CTS is lowered. Transmission will resume when CTS is raised. The FOSSIL will drop RTS when the receive buffer reaches a predetermined percentage full. The FOSSIL will raise RTS when the receive buffer empties below the predetermined percentage full. The point(s) at which this occurs is left to the individual FOSSIL implementor. 5) Enabling receive Xon/Xoff will cause the FOSSIL to send a Xoff when the receive buffer reaches a pre-determined percentage full. An Xon will be sent when the receive buffer empties below the predetermined percentage full. The point(s) at which this occurs is left to the individual FOSSIL implementor. 6) Applications using this function should set all bits ON in the high nibble of AL as well. There is a compatible (but not identical) FOSSIL driver implementation that uses the high nibble as a control mask. If your application sets the high nibble to all ones, it will always work, regardless of the method used by any given driver. entry AH 10h Extended Ctrl-C/Ctrl-K checking and transmit on/off AL flags bit mask byte (bit set if activated) bits 0 enable/disable Ctrl-C/Ctrl-K checking 1 disable/enable the transmitter 2-7 not used DX port number (NOP if DX=00FFh) return AX status byte 0000h control-C/K has not been received 0001h control-C/K has been received note This is used primarily for programs that can't trust XON/XOFF at FOSSIL level (such as BBS software). entry AH 11h FOSSIL: Set current cursor location. DH row (line) 0-24 DL column 0-79 return none note 1) This function looks exactly like the int 10h, fn 02h on the IBM PC. The cursor location is passed in DX: row in DH and column in DL. This function treats the screen as a coordinate system whose origin (0,0) is the upper left hand corner of the screen. 2) Row and column start at 0. entry AH 12h FOSSIL: Read current cursor location. return DH row (line) DL column note 1) Looks exactly like int 10h/fn 03h in the IBM PC BIOS. The current cursor location (same coordinate system as function 16h) is passed back in DX. 2) Row and column start at 0. entry AH 13h FOSSIL: Single character ANSI write to screen. AL value of character to display return none note This call might not be reentrant since ANSI processing may be through DOS. entry AH 14h FOSSIL: Enable or disable watchdog processing AL 00h to disable watchdog 01h to enable watchdog DX port number (NOP if DX=00FFh) return none note 1) This call will cause the FOSSIL to reboot the system if Carrier Detect for the specified port drops while watchdog is turned on. 2) The port need not be active for this function to work. entry AH 15h Write character to screen using BIOS support routines AL ASCII code of character to display return none note 1) This function is reentrant. 2) ANSI processing may not be assumed. entry AH 16h Insert or Delete a function from the timer tick chain AL 00h to delete a function 01h to add a function ES:DX address of function return AX 0000h successful 0FFFFh unsuccessful entry AH 17h FOSSIL: Reboot system AL boot type 00h cold boot 01h warm boot return none entry AH 18h FOSSIL: Read block CX maximum number of characters to transfer DX port number (NOP if DX=00FFh) ES:DI pointer to user buffer return AX number of characters transferred note 1) This function does not wait for more characters to become available if the value in CX exceeds the number of characters currently stored. 2) ES:DI are left unchanged by the call; the count of bytes actually transferred will be returned in AX. entry AH 19h FOSSIL: Write block CX maximum number of characters to transfer DX port number (NOP if DX=00FFh) ES:DI pointer to user buffer return AX number of characters transfered note ES and DI are not modified by this call. entry AH 1Ah FOSSIL: Break signal begin or end AL 00h stop sending 'break' 01h start sending 'break' DX port number (NOP if DX=00FFh) return none note 1) Resets all transmit flow control restraints such as an XOFF received from remote. 2) Init (fn 04h) or UnInit (fn 05h) will stop an in-progress break. 3) The application must determine the "length" of the break. entry AH 1Bh FOSSIL: Return information about the driver CX size of user buffer in bytes DX port number (if DX=00FFh, port data will not be valid) ES:DI pointer to user buffer return AX number of characters transferred ES:DI user buffer structure: 00h word size of structure in bytes 02h byte FOSSIL driver version 03h byte revision level of this specific driver 04h dword FAR pointer to ASCII ID string 08h word size of the input buffer in bytes 0Ah word number of bytes in input buffer 0Ch word size of the output buffer in bytes 0Eh word number of bytes in output buffer 10h byte width of screen in characters 11h byte screen height in characters 12h byte actual baud rate, computer to modem (see mask in function 00h note 1) The baud rate byte contains the bits that fn 00h would use to set the port to that speed. 2) The fields related to a particular port (buffer size, space left in the buffer, baud rate) will be undefined if port=0FFh or an invalid port is contained in DX. 3) Additional information will always be passed after these, so that the fields will never change with FOSSIL revision changes. entry AH 7Eh FOSSIL: Install an external application function AL code assigned to external application ES:DX pointer to entry point return AX 1954h FOSSIL driver present not 1954h FOSSIL driver not present BH 00h failed 01h successful BL code assigned to application (same as input AL) note 1) Application codes 80h-0BFh are supported. Codes 80h-83h are reserved. 2) An error code of BH=00h with AX=1954h should mean that another external application has already been installed with the code specified in AL. 3) Applications are entered via a FAR call and should make a FAR return. entry AH 7Fh FOSSIL: Remove an external application function AL code assigned to external application ES:DX pointer to entry point return AX 1954h BH 00h failed 01h successful BL code assigned to application (same as input AL) ┌─────────────────────────────────────────────────────────────────────────────┐ │Interrupt 15h Cassette I/O 3**8 │ └─────────────────────────────────────────────────────────────────────────────┘ (0:0054h) 1) Renamed "System Services" on PS/2 line. 2) Issuing int 15h on an XT may cause a system crash. On AT and after, interrupts are disabled with CLI when the interrupt service routine is called, but most ROM versions do not restore interrupts with STI. 3) For the original IBM PC, int 15h returns AH=80h and CF set for all calls with AH not 0,1, or 2. 4) For the PC/XT int 15h returns AH=86h, CF set if called at all. (the PC/XT ROM BIOS does not support int 15h) 5) For the AT/339, int 15h returns AH=86h, CF set if called with an invalid function code. Function 00h Turn Cassette Motor On (PC, PCjr only) entry AH 00h return CF set on error AH error code 00h no errors 01h CRC error 02h bad tape signals no data transitions (PCjr) 03h no data found on tape not used (PCjr) 04h no data no leader (PCjr) 80h invalid command 86h no cassette present not valid in PCjr note NOP for systems where cassette not supported. Function 01h Turn Cassette Motor Off (PC, PCjr only) entry AH 01h return CF set on error AH error code (86h) note NOP for systems where cassette not supported. Function 02h Read Blocks From Cassette (PC, PCjr only) entry AH 02h CX number of bytes to read ES:BX segment:offset + 1 of last byte read return CF set on error AH error code (01h, 02h, 04h, 80h, 86h) DX count of bytes actually read ES:BX pointer past last byte written note 1) NOP for systems where cassette not supported. 2) Cassette operations normally read 256 byte blocks. Function 03h Write Data Blocks to Cassette (PC, PCjr only) entry AH 03h CX count of bytes to write ES:BX pointer to data buffer return CF set on error AH error code (80h, 86h) CX 00h ES:BX pointer to last byte written+1 note 1) NOP for systems where cassette not supported. 2) The last block is padded to 256 bytes with zeroes if needed. 3) No errors are returned by this service. Function 0Fh ESDI Format Unit Periodic Interrupt (PS/2 50+) entry AH 0Fh AL phase code 00h reserved 01h surface analysis 02h formatting return CF clear if formatting should continue set if it should terminate note 1) Called the BIOS on the ESDI Fixed Disk Drive Adapter/A during a format or surface analysis operation after each cylinder is completed. 2) This function call can be captured by a program so that it will be notified as each cylinder is formatted or analyzed. The program can count interrupts for each phase to determine the current cylinder number. 3) The BIOS default handler for this function returns with CF set. Function 10h TopView API Function Calls (TopView) see Chapter 17 Function 20h PRINT.COM (DOS 3.1+ internal) (AT, XT/286, PS/2 50+) entry AH 20h AL subfunction 00h disable critical region flag 01h set critical region flag ES:BX pointer to flag byte set while inside DOS calls 10h set up SysReq routine 11h completion of SysReq routine (software only) Function 21h Read Power-On Self Test (POST) Error Log (PS/2 50+) entry AH 21h AL 00h read POST log 01h write POST log BH device ID BL device error code return CF set on error AH status 00h successful read BX number of POST error codes stored ES:DI pointer to error log 01h list full 80h invalid command 86h function unsupported note The log is a series of words, the first byte of which identifies the error code and the second is the device ID. Function 40h Read/Modify Profiles (Convertible) entry AH 40h AL 00h read system profile in CX,BX 01h write system profile from CX, BX 02h read internal modem profile in BX 03h write internal modem profile from BX BX profile info return BX internal modem profile (from 02h) CX,BX system profile (from 00h) Function 41h Wait On External Event (Convertible) entry AH 41h AL condition type bits 0-2 condition to wait for 0,0,0 any external event 0,0,1 compare and return if equal 0,1,0 compare and return if not equal 0,1,1 test and return if not zero 1,0,0 test and return if zero 3 reserved 4 0 user byte 1 port address 5-7 reserved BH condition compare or mask value condition codes: 00h any external event 01h compare and return if equal 02h compare and return if not equal 03h test and return if not zero 04h test and return if zero BL timeout value times 55 milliseconds 00h if no time limit DX I/O port address (if AL bit 4=1) ES:DI pointer to user byte (if AL bit 4=0) Function 42h Request System Power Off (Convertible) entry AH 42h AL 00h to use system profile 01h to force suspend regardless of profile return unknown Function 43h Read System Status (Convertible) entry AH 43h return AL status byte bit 0 LCD detached 1 reserved 2 RS232/parallel powered on 3 internal modem powered on 4 power activated by alarm 5 bad time 6 external power in use 7 battery low Function 44h (De)activate Internal Modem Power (Convertible) entry AH 44h AL 00h to power off 01h to power on return unknown Function 4Fh OS Hook - Keyboard Intercept (except PC, PCjr, and XT) entry AH 4Fh AL scan code, CF set return AL scan code CF set processing desired clear scan code should not be used note 1) Called by int 9 handler for each keystroke to translate scan codes. 2) An OS or a TSR can capture this function to filter the raw keyboard data stream. The new handler can substitute a new scan code, return the same scan code, or return the carry flag clear causing the keystroke to be discarded. The BIOS default routine simply returns the scan code unchanged. 3) A program can call int 15h/fn0C0h to determine whether the host machine's BIOS supports keyboard intercept. 4) Used internally by PC-MOS/386 v4.00+ for keyboard input. 5) Some BIOSes do not properly support this call. However, some versions of KEYB.COM provide additional 4Fh support. Function 52h MicroSoft RAM-Resident Software Specification 1.0 This standard was proposed by MicroSoft in 1986 as a common interface for TSR programs. It appears to have been largely unknown or disregarded. Function 0: Get Program Information by Name entry DS:BX The Program ID of the memory-resident program to look for return AL 0FFh if the program we are looking for is installed 00h if it is not installed CX The number of this program. The first program installed is number 0, with the second program being number 1, etc. By using a dynamic numbering system, we avoid conflicts between programs that might otherwise choose the same ID. We also provide a good way to scan all the resident programs using function 1. ES:DX pointer to the Program ID Record (PIDR) note This function tests to see if a program is memory resident and returns a pointer to its program information if it is resident. To use this function, set DS:BX to point to the program ID. Each installed program will check to see if this program ID agrees with its own internal program ID. Function 1: Get Program Information by Number entry CX Number of the program we want the information for return AL 0FFh if the program we are looking for is installed 00h if it is not installed ES:DX pointer to the Program ID Record (PIDR) note This function returns exactly the same information as function 0. The only difference is how we identify the program we want, which is determined by its position in the interrupt chain; program 0 is the last program in the chain, and the first program in the chain (usually the most recently installed) has the highest number. Function 2: Activate Program entry CX The number of the program we want to activate DS:BX Activation Record. This record will give program information on how and what it should activate within the program return none note This function activates one of the installed programs. It is useful if you want to control many desk accessories with a single control panel like the one used in SideKick. You can also use it with a program like ProKey to run a named macro under program control, or with SideKick to bring up one of the desk accessories from within a program or batch file. Function 3: Deactivate Program entry CX The number of the program we want to deactivate DS:BX Deactivation Record. This record will give program information on how and what it should deactivate within the program return none note This function is the opposite of function 2 (activate program). Function 4: Enable Program entry CX The number of the program we want to enable DS:BX Enable mask record. This mask describes what features we want to enable. A null record enables all the features. return none note This function is the opposite of function 5 (disable program). Function 5: Disable Program entry CX The number of the program we want to disable DS:BX Disable mask record. This mask describes what features we want to disable. A null record disables all the features. return none note Sometimes it becomes necessary to disable a program to prevent it from conflicting with another program, this function is designed to do that. This function is the opposite of function 4 (Enable Program). Function 70h EEROM handler (Tandy 1000HX) entry AH 00h read from EEROM BL 00h 01h write to EEROM BL word number to write (0-15) DX word value to write return DX (AH=00h) word value CF set on error (system is not a Tandy 1000 HX) Function 80h OS Hook - Device Open (AT, XT/286, PS/2) entry AH 80h BX device ID CX process ID return CF set on error AH status note 1) Acquires ownership of a logical device for a process. 2) This call, along with fns 81h and 82h, defines a simple protocol that can be used to arbitrate usage of devices by multiple processes. A multitasking program manager would be expected to capture int 15h and provide the appropriate service. 3) The default BIOS routine for this function simply returns with CF clear and AH=00h. Function 81h Device Close (AT, XT/286, PS/2) entry AH 81h BX device ID CX process ID return CF set on error AH status note 1) Releases ownership of a logical device for a process. 2) A multitasking program manager would be expected to capture int 15h and provide the appropriate service. 3) The BIOS default routine for this function simply returns with the CF clear and AH=00h. Function 82h Program Termination (AT, XT/286, PS/2) AH 82h BX device ID return CF set on error AH status note 1) Closes all logical devices opened with function 80h. 2) A multitasking program manager would be expected to capture int 15h and provide the appropriate service. 3) The BIOS default routine for this function simply returns with CF clear and AH=00h. Function 83h Event Wait (AT, XT/286, Convertible, PS/2 50+) entry AH 83h AL 00h to set interval 01h to cancel CX:DX number of microseconds to wait (granularity is 976 microseconds) ES:BX pointer to semaphore flag (bit 7 is set when interval expires) (pointer is to caller's memory) (some sources list bit 15 set) return CF clear OK set function already busy note 1) Requests setting of a semaphore after a specified interval or cancels a previous request. 2) The calling program is responsible for clearing the semaphore before requesting this function. 3) The actual duration of an event wait is always an integral multiple of 976 microseconds. The CMOS date/clock chip interrupts are used to implement this function. 4) Use of this function allows programmed, hardware-independent delays at a finer resolution than can be obtained through use of the MS-DOS Get Time function (int 21h/fn 2Ch) which returns time in hundredths of a second. 5) CX:DX is a four-byte integer. 7) This function is called by int 70h and is not the normal Int 08h/1Ch clock tick. It is generated by the MC146818A Real Time Clock chip. This is the battery backed up CMOS clock chip. Function 84h Read Joystick Input Settings (AT, XT/286, PS/2) entry AH 84h DX 00h to read the current switch settings (return in AL) 01h to read the resistive inputs return CF set on error (fn 00h) AL switch settings (bits 7-4) (fn 01h) AX stick A (X) value BX stick A (Y) value CX stick B (X) value DX stick B (Y) value note 1) An error is returned if DX does not contain a valid subfunction number. 2) If no game adapter is installed, all returned values are 00h. 3) Using a 250K Ohm joystick, the potentiometer values usually lie within the range 0-416 (0000h-01A0h). Function 85h System Request (SysReq) Key Pressed (except PC, PCjr, XT) entry AH 85h AL 00h key pressed 01h key released return CF set on error AH error code note 1) Called by BIOS keyboard decode routine when the SysReq key is detected. 2) The BIOS handler for this call is a dummy routine that always returns a success status unless called with an invalid subfunction number in AL. 3) A multitasking program manager would be expected to capture int 15h so that it can be notified when the user strikes the SysReq key. Function 86h Delay (except PC, PCjr, XT) AH 86h CX:DX 4-byte integer, number of microseconds to wait CX high word, DX low word return CF clear after wait elapses CF set immediately due to error note 1) Suspends the calling program for a specified interval in microseconds. 2) The actual duration of the wait is always an integral multiple of 976 microseconds. 3) Use of this function allows programmed, hardware-independent delays at a finer resolution than can be obtained through use of the MS-DOS Get Time function (int 21h fn 2Ch) which returns time in hundredths of a second). 4) This function calls int 70h and is not the normal Int 08h/1Ch clock tick. It is generated by the MC146818A Real Time Clock chip. This is the battery backed up CMOS clock chip. Function 87h Memory Block Move (2-3-486 machines only) AH 87h CX number of words to move ES:SI pointer to Global Descriptor Table (GDT) offset 00h-0Fh reserved, set to zero 00h null descriptor 08h uninitialized, will be made into GDT descriptor 10h-11h source segment length in bytes (2*CX-1 or greater) 12h-14h 24-bit linear source address 15h access rights byte (always 93h) 16h-17h reserved, set to zero 18h-19h destination segment length in bytes (2*CX-1 or greater) 1Ah-1Ch 24-bit linear destination address 1Dh access rights byte (always 93h) 1Eh-1Fh reserved, set to zero 20h *uninitialized, used by BIOS 28h *uninitialized, will be made into SS descriptor (*) some sources say initialized to zero return CF set on error AH status 00h success - source copied into destination 01h RAM parity error 02h exception interrupt error 03h address line 20 gating failed note 1) The GDT table is composed of six 8-byte descriptors to be used by the CPU in protected mode. The four descriptors in offsets 00h-0Fh and 20h-2Fh are filled in by the BIOS before the CPU mode switch. 2) The addresses used in the descriptor table are linear (physical) 24-bit addresses in the range 000000h-0FFFFFFh - not segments and offsets - with the least significant byte at the lowest address and the most significant byte at the highest address. 3) Interrupts are disabled during this call; use may interfere with the operation of comm programs, network drivers, or other software that relies on prompt servicing of hardware interrupts. 4) This call is not valid in the OS/2 Compatibility Box. 5) This call will move a memory block from any real or protected mode address to any other real or protected mode address. 6) DESQview does not intercept function 87, but QEXT and QEMM do, thereby allowing function 87 to work correctly inside DV. VDISK, which uses function 87, works inside DV. If VDISK is sitting at the 1 MB mark, then the int 19h vector will have a VDISK signature in it. The normal way to check for VDISK presence is by checking for the string "VDISK" at offset 12h of the segment of the int 19h vector. If the string matches, then you can determine how much extended memory is reserved for VDISK by looking at offset 2Ch is the 3-byte address of the lowest extended memory address NOT in use by VDISK (i.e. if you see at 2Ch "00 00 14" then that means that VDISK is using memory up to 1 MB + 256K). Function 88h Get Extended Memory Size (AT, XT/286, PS/2) entry AH 88h return AX number of contiguous 1K blocks of extended memory starting at address 1024k note 1) This call will not work in the OS/2 Compatibility Box. 2) Some BIOSes and software manipulate the Carry Flag when this function is called. When tested on a vanilla 386 with AMI BIOS the machine returned with the carry flag set. When 386-to-the-Max was loaded, the flag was not set. 3) Used by IBM VDISK 4.0. Function 89h Switch Processor to Protected Mode (AT, XT/286, PS/2) entry AH 89h BH interrupt number for IRQ0, written to ICW2 of 8259 PIC #1 (must be evenly divisible by 8, determines IRQ0-IRQ7) BL interrupt number for IRQ8, written to ICW2 of 8259 PIC #2 (must be evenly divisible by 8, determines IRQ8-IRQ15) ES:SI pointer to 8-entry Global Descriptor Table for protected mode: offset 00h null descriptor, initialized to zero 08h GDT descriptor 10h IDT (Interrupt Descriptor Table) descriptor 18h DS, user's data segment 20h ES, user's extra segment 28h SS, user's stack segment 30h CS, user's code segment 38h uninitialized, used to build descriptor for BIOS code segment return CF set on error AH 0FFh error enabling address line 20 CF clear function successful (CPU is in protected mode) AH 00h CS user-defined selector DS user-defined selector ES user-defined selector SS user-defined selector note 1) The user must initialize the first seven descriptors; the eighth is filled in by the BIOS to provide addressability for its own execution. The calling program may modify and use the eighth descriptor for any purpose after return from this function call. 2) Intercepted by Microsoft's HIMEM.SYS and Quarterdeck's QEMM.SYS. Function 90h Device Busy Loop (except PC, PCjr, XT) entry AH 90h AL predefined device type code: 00h disk (may timeout) 01h diskette (may timeout) 02h keyboard (no timeout) 03h PS/2 pointing device (may timeout) 80h network (no timeout) 0FCh hard disk reset (PS/2) (may timeout) 0FDh diskette motor start (may timeout) 0FEh printer (may timeout) ES:BX pointer to request block for type codes 80h through 0FFh (for network adapters ES:BX is a pointer to network control block) return CF set if wait time satisfied clear if driver must perform wait note 1) Used by NETBIOS, TOPS Network, Tom Wagner's CTASK multitasker. 2) Generic type codes are allocated as follows: 00h-7Fh non-reentrant devices; OS must arbitrate access serially reusable devices 80h-0BFh reentrant devices; ES:BX points to a unique control block 0C0h-0FFh wait-only calls, no complementary POST int 15/fn 91h call 3) Invoked by the BIOS disk, printer, network, and keyboard handlers prior to performing a programmed wait for I/O completion. 4) A multitasking program manager would be expected to capture int 15h/ fn 90h so that it can dispatch other tasks while I/O is in progress. 5) The default BIOS routine for this function simply returns with the CF clear and AH=00h. Function 91h Interrupt Completed (AT, XT/286, PS/2 50+) entry AH 91h AL type code (see AH=90h above) 00h-7Fh serially reusable devices 80h-0BFh reentrant devices ES:BX pointer to request block for type codes 80h through 0BFh return AH 00h note 1) Used by NETBIOS and TOPS network, Tom Wagner's CTASK multitasker. 2) Invoked by the BIOS disk network, and keyboard handlers to signal that I/O is complete and/or the device is ready. 3) Predefined device types that may use Device POST are: 00H disk (may timeout) 01H floppy disk (may timeout) 02H keyboard (no timeout) 03H PS/2 pointing device (may timeout) 80H network (no timeout) 4) The BIOS printer routine does not invoke this function because printer output is not interrupt driven. 5) A multitasking program manager would be expected to capture int 15h/ fn 91h so that it can be notified when I/O is completed and awaken the requesting task. 6) The default BIOS routine for this function simply returns with the CF flag clear and AH=00h. Function 0C0h Get System Configuration (XT after 1/10/86, PC Convertible, XT/286, AT, PS/2) entry AH 0C0h return CF set if BIOS doesn't support call ES:BX pointer to ROM system descriptor table bytes 00h-01h number of bytes in the following table (norm. 16 bytes) 02h system ID byte; see Chapter 2 for interpretation 03h secondary ID distingushes between AT and XT/286, etc. 04h BIOS revision level, 0 for 1st release, 1 for 2nd, etc. 05h feature information byte bits 0 reserved 1 Micro Channel bus (instead of ISA or EISA) 2 extended BIOS area allocated at 640k 3 wait for external event supported (int 15fn41) used on Convertible; reserved on PS/2 systems 4 kbd intrcpt:int 15h, fn 04h called upon int 09h 5 realtime clock installed 6 second 8259 installed (cascaded IRQ2) 7 DMA channel 3 - used by hard disk BIOS 06h unknown (set to 0) (reserved by IBM) 07h unknown (set to 0) (reserved by IBM) 08h unknown (set to 0) 09h unknown (set to 0) (Award BIOS copyright here) note 1) Int 15h is also used for the Multitask Hook on PS/2 machines. No register settings available yet. 2) The 1/10/86 XT BIOS returns an incorrect value for the feature byte. 3) Novell documents some versions of Netware prior to 2.2 as having problems on PS/2 machines due to a bug which did not return from the interrupt correctly. 4) Some AMI BIOSes do not support this function. (early Dell machines) Function 0C1h Return Extended BIOS Data Area Segment Address (PS/2) entry AH 0C1h return CF set on error ES segment of XBIOS data area note 1) The XBIOS Data Area is allocated at the high end of conventional memory during the POST (Power-On-Self-Test) sequence. 2) The word at 0040:0013h (memory size) is updated to reflect the reduced amount of memory available for DOS and application programs. 3) The 1st byte in the XBIOS Data Area is initialized to its length in K. 4) A program can determine whether the XBIOS Data Area exists by using int 15h/fn 0C0h. Function 0C2h Pointing Device BIOS Interface (DesQview 2.x) (PS/2) entry AH 0C2h AL 00h Enable/Disable Pointing Device BH 00h disable 01h enable 01h Reset Pointing Device Resets the system's mouse or other pointing device, sets the sample rate, resolution, and other characteristics to their default values. return BH device ID (0=first) note 1) After a reset operation, the state of the pointing device is as follows: disabled; sample rate at 100 reports per second; resolution at 4 counts per millimeter; scaling at 1 to 1. 2) The data package size is unchanged by this fn. 3) Apps can use the fn 0C2h subfunctions to initialize the pointing device to other parms, then enable the device with fn 00h. 4) BL is altered on return. 02h Set Sampling Rate BH 00h 10/second 01h 20/second 02h 40/second 03h 60/second 04h 80/second 05h 100/second (default) 06h 200/second 03h Set Pointing Device Resolution BH 00h one count per mm 01h two counts per mm 02h four counts per mm (default) 03h eight counts per mm 04h Get Pointing Device Type return BH ID code for the mouse or other pointing device 05h Initialize Pointing Device Interface Sets the data package size for the system's mouse or other pointing device, and initializes the resolution, sampling rate, and scaling to their default values. BH data package size (1 - 8 bytes) note After this operation, the state of the pointing device is as follows: a) disabled; b) sample rate at 100 reports per second; c) resolution at 4 counts per millimeter; d) scaling set at 1 to 1. 06h Get Status or Set Scaling Factor Returns the current status of the system's mouse or other pointing device or sets the device's scaling factor. BH 00h return device status return BL status byte bits 0 set if right button pressed 1 reserved 2 set if left button pressed 3 reserved 4 0 1:1 scaling 1 2:1 scaling 5 0 device disabled 1 device enabled 6 0 stream mode 1 remote mode 7 reserved CL resolution 00h 1 count per millimeter 01h 2 counts per millimeter 02h 4 counts per millimeter 03h 8 counts per millimeter DL sample rate (hex count) 0Ah 10 reports per second 14h 20 reports per second 28h 40 reports per second 3Ch 60 reports per second 50h 80 reports per second 64h 100 reports per second 0C8h 200 reports per second 01h set scaling to 1:1 02h set scaling to 2:1 07h Set Pointing Device Handler Address Notifies BIOS pointing device driver of the address for a routine to be called each time pointing device data is available. ES:BX address of user device handler return AL 00h return CF set on error AH status 00h successful 01h invalid function 02h invalid input 03h interface error 04h need to resend 05h no device handler installed note 1) The values in BH for those functions that take it as input are stored in different locations for each subfunction. 2) The user's handler for pointing device data is entered via a far call with four parameters on the stack: SS:SP+0Ah status SS:SP+08h x coordinate SS:SP+06h y coordinate SS:SP+04h z coordinate (always 0) The handler must exit via a far return without removing the parameters from the stack. 3) The status parameter word passed to the user's handler is interpreted as follows: bits 0 left button pressed 1 right button pressed 2-3 reserved 4 sign of x data is negative 5 sign of y data is negative 6 x data has overflowed 7 y data has overflowed 8-0Fh reserved Function 0C3h Enable/Disable Watchdog Timeout (PS/2 50+) entry AH 0C3h AL 00h disable watchdog 01h enable watchdog BX timer counter return CF set on error note 1) The watchdog timer generates an NMI. 2) This would be subject to protection with a real OS so temporary masters would not be able to seize the bus forever. Function 0C4h Programmable Option Select (PS/2 50+) entry AH 0C4h AL 00h return base POS register address 01h enable slot BL slot number 02h enable adapter return CF set on error DX base POS register address (if function 00h) note 1) Fn 00h returns the base Programmable Option Select register address, enables a slot for setup, or enables an adapter. 2) Valid on machines with Micro Channel Architecture (MCA) bus only. 3) After a slot is enabled with fn 01h, specific information can be obtained for the adapter in that slot by performing port input operations: Port Function 100h MCA ID (low byte) 101h MCA ID (high byte) 102h Option Select Byte 1 bit 0 0 if disabled 1 if enabled 103h Option Select Byte 2 104h Option Select Byte 3 105h Option Select Byte 4 bits 6-7 are channel check indicators 106h Subaddress Extension (low byte) 107h Subaddress Extension (high byte) Function 0C5h Used by PS/2 Model 50+ and Olivetti MCA machines Used by Desqview 2.2 Used by Lotus 123 Release 2.2 Used by Microsoft Word 5.0 note Functions unknown. Reported by InfoWorld Nov 13 1989's Micro Channel 386 test as a conflict between the above software packages. InfoWorld said that Quarterdeck (Desqview) was working on a fix for their product. No other information. Function 0DEh DesQview Services (DesQview) ┌─────────────────────────────────────────────────────────────────────────────┐ │Interrupt 16h Keyboard I/O 3**9 │ └─────────────────────────────────────────────────────────────────────────────┘ (0:0058h) Access the keyboard. Scancodes are found in Appendix 1. ASCII codes are found in Appendix 2. IBM's original keyboard layout is referred to as the 84-key or "old style". It has the function keys on the left and an embedded cursor/numeric keypad on the right. The 101-key "new style" or "enhanced" keyboard (such as used on the PS/2s) adds several keys. The early BIOS will not detect the new scancodes and the new BIOS for some reason added new function calls for this purpose instead of enhancing the old ones. This causes some hassle when writing programs which need to support both keyboards fully. Most programs limit themselves to the 84-key functions in the interest of backward compatibility. The SWITCHES CONFIG.SYS command forces DOS 4.0 to use the standard int 16h requests for keyboard I/O rather than the extended int 16h requests. The DOS KEYB command does not hook into the BIOS. It is a total replacement for the BIOS int9 driver. The only good thing about this is that you can use 101-key keyboards on old ATs without support for enhanced keyboards. KEYB is very peculiar in its handling of the keyboard, causing some programs to break. It also tends to disable interrupts for a long time while process- ing each scan code. There are machines such as the Toshiba 5200 which have 84-key layouts but "simulate" being 101-key, at least as far as int 16 goes. (always good for confusing your software...) Function 00h Get Keyboard Input - read the next character in keyboard buffer, if no key ready, wait for one. entry AH 00h return AH scan code AL ASCII character note 1) Removes keystroke from buffer (destructive read). 2) Does not work with the extra keys on the 101-key "enhanced" keyboard. Function 01h Check Keystroke Buffer - Do Not Clear entry AH 01h return ZF 0 (clear) if character in buffer 1 (set) if no character in buffer AH scan code of character (if ZF=0) AL ASCII character if applicable note 1) Keystroke is not removed from buffer. The same character and scan code will be returned by the next call to Int 16h/fn 00h. 2) This call flushes the 101-key codes from the buffer if they precede an 84-key code. Function 02h Shift Status - fetch bit flags indicating shift status entry AH 02h return AL status byte (same as [0040:0017]) bits 7 Insert on 6 CapsLock on 5 NumLock on 4 ScrollLock on 3 Alt key down 2 Control key down 1 Left shift (left caps-shift key) down 0 Right shift (right caps-shift key) down note The Keyboard Flags Byte is stored in the BIOS Data Area at 0000:0417h. Function 03h Keyboard - Set Repeat Rate (PCjr, AT, XT/286, PS/2) entry AH 03h AL 00h reset typematic defaults (PCjr) 01h increase initial delay (PCjr) 02h decrease repeat rate by 1/2 (PCjr) 03h increase both delays by 1/2 (PCjr) 04h turn off typematic (PCjr) 05h set typematic rate (AT, PS/2) BH 00h-03h for delays of 250ms, 500ms, 750ms, or 1 second 0,0 250ms 0,1 500ms 1,0 750ms 1,1 1 second BL 00h-1Fh for typematic rates of 30cps down to 2cps 00000 30 01011 10.9 10101 4.5 00001 26.7 01100 10 10110 4.3 00010 24 01101 9.2 10111 4 00011 21.8 01110 8.6 11000 3.7 00100 20 01111 8 11001 3.3 00101 18.5 10000 7.5 11010 3 00110 17.1 10001 6.7 11011 2.7 00111 16 10010 6 11100 2.5 01000 15 10011 5.5 11101 2.3 01001 13.3 10011 5.5 11110 2.1 01010 12 10100 5 11111 2 return nothing note 1) Subfunction 05h is available on ATs with ROM BIOS dated 11/15/85 and later, the XT/286, and the PS/2. 2) Subfunction 0 (Return to Default Keyboard State) restores the keyboard to its original state. The original state at power-on is typematic on, normal initial delay and normal typematic rate. 3) Subfunction 1 (Increase Initial Delay) increases the delay between the first character typed and the burst of typematic characters. 4) For Subfunctions 0 through 4, each time the typematic rate is changed, all previous states are removed. 5) Some clone keyboards (Northgate Omnikey and Focus) have much higher repeat rates for the same bit values. Function 04h Keyboard Click Toggle (PCjr and Convertible) entry AH 04h AL 00h for click off 01h for click on return nothing Function 05h Load Keyboard Buffer (AT or PS/2 with enhanced kbd) entry AH 05h CH scan code CL ASCII character return CF set on error AL 00h success 01h if buffer full note Places a character and scan code at the end of the keyboard type-ahead buffer. Function 06h Keyboard Buffer Write (Fansi-Console to 2.00) entry AH 06h BX extended key value to place in typeahead buffer return unknown note This call may be dropped since it now duplicates function 05h. Function 07h Change Shift Key Status (Fansi-Console to 2.00) entry AH 07h AL shift key status value return unknown note Status byte is same as function 02h. Function 10h Get Enhanced Keystroke And Read (F11, F12 Enhanced Keyb'd) (XT/286, PS/2, AT with "Enhanced" keyboard) entry AH 10h return AH scan code AL ASCII character if applicable note 1) Reads a character and scan code from the keyboard type-ahead buffer. 2) Use this function for the enhanced keyboard instead of int 16h fn 00h. It allows applications to obtain the scan codes for the additional F11, F12, and cursor control keys. 3) This is the enhanced version of function 00h. Function 11h Check Enhanced Keystroke (F11-F12 on enhanced keyboard) (XT/286, PS/2, AT with "Enhanced" keyboard) entry AH 11h return ZF 0 (clear) if key pressed AH scan code AL ASCII character if applicable 1 if buffer is empty note 1) Keystroke is not removed from buffer. The same char and scan code will be returned by the next call to Int 16h/fn 10h. 2) Use this function for the enhanced keyboard instead of int 16h/fn 00h. It allows applications to test for the additional F11, F12, and cursor control keys. Function 12h Extended Get Shift Status (F11, F12 Enhanced keyboard) entry AH 12h return AX status word AL bit 0 right Shift key depressed 1 left Shift key depressed 2 Control key depressed 3 Alt key depressed 4 ScrollLock state active 5 NumLock state active 6 CapsLock state active 7 insert state is active AH bit 0 left Control key pressed 1 left Alt key depressed 2 right Control key pressed 3 right Alt key depressed 4 Scroll Lock key depressed 5 NumLock key depressed 6 CapsLock key depressed 7 SysReq key depressed note Use this function for the enhanced keyboard instead of int 16h/fn 02h. Function 70h, 71h, 72h Internal Functions (SEAware's FAKEY.COM) note FAKEY.COM is a TSR keyboard utility distributed to registered users of SEAware products. Function 75h Set Tick Count for Scanning (pcAnywhere 2.00) entry AH 75h AL tick count return none note 1) Sets count of 55ms timer ticks between checks for new screen changes. 2) pcAnywhere is a program that allows operation of a remote machine over a serial link. Function 76h Set Error Checking Mode (pcAnywhere 2.00) entry AH 76h AL error checking type 00h none 01h fast 02h slow return none Function 77h reserved (pcAnywhere 2.00) pcAnywhere API - reserved Function 78h Log Off (pcAnywhere 2.00) entry AL 00h wait for another call 01h exit but remain TSR 02h automatic mode - watches DTR 0FFh leave in current operating mode (pcAnywhere 2.1) return none Function 79h Installation Check (pcAnywhere 2.00) entry AH 79h AL 00h installation check return AX 0FFFFh resident and active 0FFFEh resident but not active 0FFFDh resident TSR 0FFFCh automatic mode any other value - not resident Function 7Ah Cancel pcAnywhere Session (pcAnywhere 2.00) entry AH 7Ah return none note Leaves pcAnywhere resident but unable to answer another call. Function 7Bh Enable/Disable Operation (pcAnywhere 2.00) entry AH 7Bh AL state 00h disabled 01h enabled return none note Remote screen is automatically refreshed when session is enabled. Function 7Ch Get Port Configuration (pcAnywhere 2.00) entry AH 7Ch return AH port number in binary (0-15) AL baud rate 00h 50 01h 75 02h 110 03h 134.5 04h 150 05h 300 06h 600 07h 1200 08h 1800 09h 2000 0Ah 2400 0Bh 4800 0Ch 7200 0Dh 9600 0Fh 19,200 Function 7Dh Get/Set Terminal Parameters (pcAnywhere 2.00) entry AH 7Dh AL 00h set parameters 01h get parameters 02h get configuration header and terminal parameters CX:DS address of Terminal Parameter Block return AL 00h nothing 01h current Terminal Parameter Block in CX:DS 02h configuration header and Terminal Parameter Block in CX:DS note Terminal Parameter Block format: (1152 bytes) (decimal) 384 bytes CRT Control Information bytes function 1-8 cursor up 9-16 cursor down 17-24 cursor left 25-32 cursor right 33-40 cursor home 41-48 clear screen 49-56 clear to end of line 57-64 clear to end of page 65-72 insert line 73-80 delete line 81-88 insert character 89-96 delete character 97-104 cursor position lead in 105-112 between row and column 113-120 after cursor position 121-128 CRT initialization 256 bytes Character Translation Table translates ASCII characters from host. Normally changes IBM graphics characters to other displayable symbols 512 bytes keyboard sequences 641-644 cursor up 645-648 cursor down 649-652 cursor left 653-656 cursor right 657-660 home 661-664 end 665-668 PgUp 669-672 PgDn 673-676 insert 677-680 delete 681-684 control-home 685-688 control-end 689-692 control-PgUp 693-696 control-PgDn 697-700 escape 701-740 F1...F10 741-780 sF1...sF10 781-820 ^F1...^F10 821-860 aF1...aF10 861-964 alt A-Z 965-1004 alt 0-9 1005-1008 alt = 1009-1012 alt - 1013-1016 print screen 1017-1020 ctrl-left arrow 1021-1024 ctrl-right arrow 1025-1120 reserved 1121-1124 begin conv. mode 1125-1128 remote printing off 1129-1132 remote printing on 1133-1136 backspace 1137-1140 refresh screen 1141-1144 send next code 1145-1148 display top 24 lines 1149-1152 display bottom 24 lines Function 7Eh Serial I/O Through pcAnywhere Port (pcAnywhere 2.00) entry AH 7Eh AL I/O function 01h get port input status 02h get port input character 03h output character 04h hang up phone CX ASCII character to output (fn 03h) return (if AL=01h) AX 00h no character ready 01h character is available (if AL=02h) AL ASCII code received Function 7Fh Set Keyboard/Screen Mode (pcAnywhere 2.00) entry AH 7Fh AL parameters 00h enable remote keyboard only | 01h enable host keyboard only | keyboard group 02h enable both keyboards | 08h display top 24 lines | screen group 09h display bottom 24 lines | 10h Hayes modem | 11h other modems | modem group 12h direct connect | Function 0EDh Borland Turbo Lightning API (partial) entry AH 0EDh BH 0EDh BL function 00h installation check 02h pointer to Lightning internal data structure lobyte 03h pointer to Lightning internal data structure hibyte 04h load auxiliary dictionary 06h autoproof mode 0Fh get number of substitutions (segment) DS:DI pointer to string to be processed return AX error code (unknown) note I've made several attempts to get a copy of the Turbo Lightning API, which was originally supposed to be available for developers in 1985. In 1988 Borland sent me a letter saying they were still working on it. In late 1989 the Borland rep on BIX told me basically that there were no plans for releasing the API any more. The information here was dredged from Chris Dunford's LSPELL.PAS interface into Lighting. Function 0F0h Set CPU speed (Compaq 386) entry AH 0F0h set speed AL speed 00h equivalent to 6 mHz 80286 (COMMON) 01h equivalent to 8 mHz 80286 (FAST) 02h full 16 mHz (HIGH) 03h toggles between 8 mHz-equivalent and speed set by system board switch (AUTO or HIGH) 04h-07h unknown 08h full 16 mHz except 8 mHz-equivalent during floppy disk access 09h specify speed directly CX speed value, 1 (slowest) to 50 (full), 3 ~=8088 return none? note 1) Used by Compaq DOS MODE command. Function 0F1h Read Current CPU Speed (Compaq 386) entry AH 0F1h return AL speed code (see function 0F0h above) if AL=09h, CX=speed code Function 0F2h Determine Attached Keyboard Type (Compaq 386) entry AH 0F2h return AL type 00h if 11-bit AT keyboard is in use 01h if 9-bit PC keyboard is in use Function 0FFh PC-Tools API entry AH 0FFh other parameters unknown note PC-Tools is a Swiss-army-knife software package with an editor, DOS shell, cache, disk optimizer, and several other functions from Central Point Software. Function 0FFh 2-The-Max VGA-16 Board entry AH 0FFh query zoom interrupt return AL zoom interrupt number AL+1 old BIOS keyboard handler interrupt number BX hot key Function 0FFh Programmer Interface to Carbon Copy Plus (5.0) entry AH 0FFh AL 00h check connection between CC and CCHELP return BL 00h Carbon Copy not connected to CCHELP 01h Carbon Copy is connected to CCHELP entry AL 01h disconnects and resets the line if the Host or CC side is connected to CCHELP entry AL 02h return a pointer to the last phone number dialed by CC return ES:DI dword pointer to ASCIIZ phone number string ┌─────────────────────────────────────────────────────────────────────────────┐ │Interrupt 17h Printer 3**10 │ └─────────────────────────────────────────────────────────────────────────────┘ (0:005Ch) access the parallel printer(s) AH is changed. All other registers left alone. Printer ports vary widely in compatibility, since the original IBM MDA's parallel port did not match its own spec. Many parallel ports do not use IRQ7 at all. The parallel port on a monochrome adapter is at 3BCh. The port on a parallel printer adapter is at 378h or 278h. At boot time, the BIOS looks at them in the order 3BCh, 378h, 278h, and assigns the first port it finds to LPT1, the second to LPT2, etc. If you have a monochrome adapter, LPT1 is probably 3BCh; otherwise, it is probably 378h. Function 00h Print Character/send AL to printer DX (0, 1, or 2) entry AH 00h AL ASCII character code DX printer to be used 00h PRN or LPT1 01h LPT2 02h LPT3 return AH status byte bits 0 time out 1 unused 2 unused 3 I/O error 4 printer selected 5 out of paper 6 acknowledge 7 not busy Function 01h Initialize Printer - set init line low, send 0Ch to printer DX entry AH 01h DX printer port to be initialized (0,1,2) return status as below Function 02h Printer Status - read status of printer DX into AH entry AH 02h DX printer port to be used (0,1,2) return AH status byte bits 7 0 busy/paused: the printer cannot immediately take more data because it is in the middle of accepting a character, printing a line, is offline, or it is in error status. 1 ready 6 ACKnowledge line toggled: reflects the state of the ACK line on the printer port at the moment the status was read. ACK is a strobe: it goes low for a very short time (12 microseconds on an Epson) when the printer is ready for another character. As far as printer status is concerned, this is useless; it's only useful for something like an interrupt-driven interface. Most of the time, you'll see ACK high (bit 6 on), but occasionally, if you check status just after sending a character, you might see it low. ACK is low when the printer is powered off. 5 out-of-paper line toggled 4 printer selected: printer is selected/ready/online. There is usually a button on the printer to control this. 3 I/O error: offline, out of paper or other error condition such as out of ribbon. 2 unused 1 unused 0 timeout error: printer failed to send ACK and drop busy after being sent a character. note 1) You can expect to see these states in a properly functioning printer: Normal Offline Power off ====== ======= ========= not busy/paused busy/paused busy/paused not out of paper not out of paper not out of paper selected/online not selected/online not selected/online not I/O error I/O error (usually) I/O error not timeout error not timeout error not timeout error 2) Not all printers return the status codes properly. That's OK, not all clone BIOS do it right either. If your program depends on the return codes, you might want to make the code easily patched or configured for nonstandard hardware. Function 03h Versa-Spool print spooler entry AH 03h Versa-Spool AL 00h Return Signature 01h Toggle Pause 02h Clear Buffer 03h Request Pause Condition 04h Request Free Buffer Space 05h Request Total Buffer Size 06h Redirect Output to LPT1 07h Redirect Output to LPT2 08h Redirect Output to LPT3 09h Request Output Device 0Ah Request Output Speed 0Bh Request Device Spooled Status return (AH=00h) AX 1234h if Versa-Spool is installed undefined if not installed (AH=01h) AX 0001h if paused 0000h if resumed (AH=02h) AX 0302h not cleared 0000h cleared (AH=03h) AX 0001h if paused 0000h if resumed (AH=04h) AX remaining buffer space (in Kbytes) (AH=05h) AX total buffer space (in Kbytes) (AH=06h) AX nothing (AH=07h) AX nothing (AH=08h) AX nothing (AH=09h) AX printer output (0..2) (AH=0Ah) AX output speed in CPS (AH=0Bh) AX 0001h is spooled 0000h otherwise Function 0C0h PC Magazine PCSPOOL - get printer status entry AH 0C0h DX printer port to be used (0,1,2) return ES:BX address of printer control block note PC Magazine, January 15, 1991. (Vol 10, Number 1) Function 0C1h PC Magazine PCSPOOL - add pause to spool queue entry AH 0C1h DX printer port to be used (0,1,2) DS:SI pointer to ASCIIZ string to display return AH printer status Function 0C2h PC Magazine PCSPOOL - flush queue record entry AH 0C2h DX printer port to be used (0,1,2) return AH printer status Function 0C3h PC Magazine PCSPOOL - cancel printer queue entry AH 0C3h DX printer port to be used (0,1,2) return AH printer status Function 0C4h PC Magazine PCSPOOL - determine of spooler is active entry AH 0C4h return DI 0B0BFh if PCSPOOL is loaded SI segment of the PSP of the active PCSPOOL ┌─────────────────────────────────────────────────────────────────────────────┐ │Interrupt 18h ROM BASIC 3**11 │ └─────────────────────────────────────────────────────────────────────────────┘ (0:0060h) Execute ROM BASIC at address 0F600h:0000h entry no parameters used return jumps into ROM BASIC on IBM systems note 1) Often reboots a compatible. 2) Used by Turbo C 1.5. 2.0 and later do not use it. 3) On IBM systems, this interrupt is called if disk boot failure occurs. 4) Video interrupt on DEC Rainbow. 5) Digital Research's ROM-based implementation of DR-DOS uses int 18h as the initial entry vector into the operating system code. Note that some clone BIOSes may not properly implement int 18h in the ROM and use of DR-DOS ROMs may not always work. 6) Maxon 286/HD laptop: called by BIOS power management routines to communicate with applications. ┌─────────────────────────────────────────────────────────────────────────────┐ │Interrupt 19h Bootstrap Loader / Extended Memory VDISK ID 3**12 │ └─────────────────────────────────────────────────────────────────────────────┘ (0:0064h) entry no parameters used return none note 1) Reads track 0, sector 1 into address 0000h:7C00h, then transfers control to that address. If no diskette drive available, looks at absolute address C:800 for a valid hard disk or other ROM. If none, transfers to ROM-BASIC via int 18h or displays loader error message. 2) Causes reboot of disk system if invoked while running. (no memory test performed). 3) If location 0000:0472h does not contain the value 1234h, a memory test (POST) will be performed before reading the boot sector. 4) VDISK from DOS 3.0+ traps this vector to determine when the CPU has shifted from protected mode to real mode. A detailed discussion can be found by Ray Duncan in PC Magazine, May 30, 1989. 5) Reportedly, some versions of DOS 2.x and all versions of DOS 3.x+ intercept int 19h in order to restore some interrupt vectors DOS takes over, in order to put the machine back to a cleaner state for the reboot, since the POST will not be run on the int 19h. These vectors are reported to be: 02h, 08h, 09h, 0Ah, 0Bh, 0Ch, 0Dh, 0Eh, 70h, 72h, 73h, 74h, 75h, 76h, and 77h. After restoring these, it restores the original int 19h vector and calls int 19h. 6) The system checks for installed ROMs by searching memory from 0C000h to the beginning of the BIOS, in 2k chunks. ROM memory is identified if it starts with the word 0AA55h. It is followed a one byte field length of the ROM (divided by 512). If ROM is found, the BIOS will call the ROM at an offset of 3 from the beginning. This feature was not supported in the earliest PC machines. The last task turns control over to the bootstrap loader (assuming the floppy controller is operational). 7) 8255 port 60h bit 0 = 1 if booting from diskette. ┌─────────────────────────────────────────────────────────────────────────────┐ │Interrupt 1Ah Time of Day 3**13 │ └─────────────────────────────────────────────────────────────────────────────┘ (0:0068h) 1) Accesses the PC internal clock. 2) This interrupt is not supported on some machines, such as the HP150 PC. 3) Some "turbo" BIOSes run the clock slower than normal in order to throw off benchmark software, which usually uses int 1Ah for timekeeping. 4) Counts occur at the rate of 1193180/65536 counts/sec (about 18.2 per second). Function 00h Read System Timer Tick Counter (except PC) entry AH 00h return AL 00h if clock was read or written (via AH=0,1) within the current 24-hour period. <>0 midnight was passed since last read CX:DX 32-bit tick count (high 16 bits in CX) note 1) The returned value is the cumulative number of clock ticks since midnight. There are 18.2 clock ticks per second, or one every 54.92ms. When the counter reaches 1,573,040, it is cleared to zero, and the rollover flag is set. 2) The rollover flag is cleared by this function call, so the flag will only be returned nonzero once per day. 3) Int 1Ah/fn 01h can be used to set the counter to an arbitrary 32 bit value. 4) This function does not return seconds/100 in DL. The best you can do is set it to zero (or any value <=99). This means that your DOS clock could be up to 1 second off from the BIOS clock, however the effect is not cumulative. Function 01h Set Clock Tick Counter Value (except PC) entry AH 01h CX:DX 32-bit high word/low word count of timer ticks return none note 1) The clock ticks are incremented by timer interrupt at 18.2065 times per second or 54.9254 milliseconds/count. Therefore: counts per second 18 (12h) counts per minute 1092 (444h) counts per hour 65543 (10011h) counts per day 1573040 (1800B0h) 2) The counter is zeroed when system is rebooted. 3) Stores a 32-bit value in the clock tick counter. 4) The rollover flag is cleared by this call. Function 02h Read Real Time Clock Time (AT and after) entry AH 02h return CH hours in BCD CL minutes in BCD DH seconds in BCD DL 00h standard time 01h daylight savings time CF 0 if clock running 1 if clock not operating note 1) Reads the current time from the CMOS time/date chip. 2) Also for Leading Edge Model M. 3) According to Phoenix this call will fail if the BIOS is "updating" its clock value. You should check the carry flag and retry if it is set following the call. Function 03h Set Real Time Clock Time (AT and after) entry AH 03h CH hours in BCD CL minutes in BCD DH seconds in BCD DL 0 (clear) if standard time 1 (set) if daylight savings time option return none note 1) Sets the time in the CMOS time/date chip. 2) Also for Leading Edge Model M. Function 04h Read Real Time Clock Date (AT and after) entry AH 04h return CH century in BCD (19 or 20) CL year in BCD DH month in BCD DL day in BCD CF 0 (clear) if clock is running 1 (set) if clock is not operating note 1) Reads the current date from the CMOS time/date chip. 2) Also for Leading Edge Model M. Function 05h Set Real Time Clock Date (AT and after) entry AH 05h CH century in BCD (19 or 20) CL year in BCD DH month in BCD DL day in BCD return none note 1) Sets the date in the CMOS time/date chip. 2) Also for Leading Edge Model M. Function 06h Set Real Time Clock Alarm (AT and after) entry AH 06h CH hours in BCD CL minutes in BCD DH seconds in BCD return CF set if alarm already set or clock inoperable note 1) Sets alarm in the CMOS date/time chip. Int 4Ah occurs at specified alarm time every 24hrs until reset with Int 1Ah/fn 07h. 2) A side effect of this function is that the clock chip's interrupt level (IRQ8) is enabled. 3) Only one alarm may be active at any given time. 4) The program using this function must place the address of its interrupt handler for the alarm in the vector for Int 4Ah. Function 07h Reset Real Time Clock Alarm (AT and after) entry AH 07h return none note 1) Cancels any pending alarm request on the CMOS date/time chip. 2) This function does not disable the clock chip's interrupt level (IRQ8). Function 08h Set Real Time Clock Activated Power On Mode (Convertible) entry AH 08h CH hours in BCD CL minutes in BCD DH seconds in BCD Function 09h Read Real Time Clock Alarm Time and Status (Convertible and PS/2 Model 30) entry AH 09h return CH hours in BCD CL minutes in BCD DH seconds in BCD DL alarm status: 00h if alarm not enabled 01h if alarm enabled but will not power up system 02h if alarm will power up system Function 0Ah Read System-Timer Day Counter (PS/2) entry AH 0Ah return CF set on error CX count of days since Jan 1,1980 note Returns the contents of the system's day counter. Function 0Bh Set System-Timer Day Counter (PS/2) entry AH 0Bh CX count of days since Jan 1,1980 return CF set on error note Stores an arbitrary value in the system's day counter. Function 80h Set Up Sound Multiplexor (PCjr) (Tandy 1000?) entry AH 80h AL sound source 00h source is 8253 timer chip, channel 2 01h source is cassette input 02h source is I/O channel "audio in" line 03h source is TI sound generator chip return none note Sets up the source for tones that will appear on the PCjr's Audio Out bus line or RF modulator. Function 1Ah Read Time and Date (AT&T 6300) entry AH 0FEh return BX days count (1=Jan 1, 1984) CH hours CL minutes DH seconds DL hundredths note Day count in BX is unique to AT&T/Olivetti computers. ┌─────────────────────────────────────────────────────────────────────────────┐ │Interrupt 1Bh Control-Break 3**14 │ └─────────────────────────────────────────────────────────────────────────────┘ (0:006Ch) This interrupt is called when the keyboard handler of the IBM machines detects Ctrl and Break pressed at the same time. DOS normally point this interrupt at its own Ctrl-Break handler. note 1) If the break occurred while processing an interrupt, one or more end of interrupt commands must be send to the 8259 Programmable Interrupt Controller. 2) All I/O devices should be reset in case an operation was underway at the time. 3) It is normally pointed to an IRET during system initialization so that it does nothing, but some programs change it to return a Ctrl-C scan code and thus invoke int 23h. ┌─────────────────────────────────────────────────────────────────────────────┐ │Interrupt 1Ch Timer Tick 3**15 │ └─────────────────────────────────────────────────────────────────────────────┘ (0:0070h) note 1) Taken 18.2065 times per second by the int 08h interrupt. 2) Normally vectors to dummy IRET unless PRINT.COM has been installed. 3) If an application moves the interrupt pointer, it is the responsibility of that application to save and restore all registers that may be modified. 4) returns values at absolute address 40:6x (BIOS Data Area); number of ticks since midnight 40:6C word timer counter high word 40:6E word timer counter low word 5) Ventura Publisher 2.0 grabs this interrupt and does not pass subsequent vector reassignments along. This causes problems with some TSRs and network software. 6) When installing a user interrupt for int 1Ch, the external interrupts must be disabled before the vector is altered. If a timer interrupt occurs between the setting of the offset and segment, an incorrect address will result. ┌─────────────────────────────────────────────────────────────────────────────┐ │Interrupt 1Dh Vector of Video Initialization Parameters 3**16 │ └─────────────────────────────────────────────────────────────────────────────┘ (0:0074h) This doubleword address points to 3 sets of 16-bytes containing data to initialize for video modes for video modes 0 & 1 (40 column), 2 & 3 (80 column), and 4, 5 & 6 (graphics) on the Motorola 6845 CRT controller chip. 6845 registers: R0 horizontal total (horizontal sync in characters) R1 horizontal displayed (characters per line) R2 horizontal sync position (move display left or right) R3 sync width (vertical and horizontal pulse: 4-bits each) R4 vertical total (total character lines) R5 vertical adjust (adjust for 50 or 60 Hz refresh) R6 vertical displayed (lines of chars displayed) R7 vertical sync position (lines shifted up or down) R8 interlace (bits 4 and 5) and skew (bits 6 and 7) R9 max scan line addr (scan lines per character row) R10 cursor start (starting scan line of cursor) R11 cursor stop (ending scan line of cursor) R12 video memory start address high byte (6 bits) R13 video memory start address low byte (8 bits) R14 cursor address high byte (6 bits) R15 cursor address low byte (8 bits) 6845 Video Init Tables: table for modes 0 and 1 \ table for modes 2 and 3 \ each table is 16 bytes long and table for modes 4,5, and 6 / contains values for 6845 registers table for mode 7 / 4 words size of video RAM for modes 0/1, 2/3, 4/5, and 6/7 8 bytes number of columns in each mode 8 bytes video controller mode byte for each mode note 1) There are 4 separate tables, and all 4 must be initialized if all video modes will be used. 2) The power-on initialization code of the computer points this vector to the ROM BIOS video routines. 3) IBM recommends that if this table needs to be modified, it should be copied into RAM and only the necessary changes made. ┌─────────────────────────────────────────────────────────────────────────────┐ │Interrupt 1Eh Vector of Diskette Controller Parameters 3**17 │ └─────────────────────────────────────────────────────────────────────────────┘ (0:0078h) Dword address points to data base table that is used by BIOS. Default location is at 0F000:0EFC7h. 11-byte table format: bytes: 00h 4-bit step rate, 4-bit head unload time 01h 7-bit head load time, 1-bit DMA flag 02h 54.9254 ms ticks - delay til motor off (36-38 typical) 03h sector size: 00h 128 bytes 01h 256 bytes 02h 512 bytes 03h 1024 bytes 04h last sector on track (8 or 9 typical) 05h inter-sector gap on read/write (42 typical) 06h data length for DMA transfers (0FFh typical) 07h gap length between sectors for format (80 typical) 08h sector fill byte for format (0F6h typical) 09h head settle time (in milliseconds) (15 to 25 typical) DOS 1.0 0 DOS 1.10 0 DOS 2.10 15 DOS 3.1 1 0Ah motor start time (in 1/8 sec intervals) (2-4 typical) DOS 2.10 2 note 1) This vector is pointed to the ROM BIOS diskette tables on system initialization 2) IBM recommends that if this table needs to be modified, it should be copied into RAM and only the necessary changes made. 3) Some versions of DOS 3.2 may contain a bug. DOS 3.2 assumes that the dword at 0070:0F37 contains the address of the diskette parameter block and changes values in that block. The location does contain a copy of the value at 0:78 (int 1Eh, DISK_POINTER) if DOS is booted from diskette, but when booted from the hard disk, the location contains 0:0. This leads to strange things, especially when running under a debugger since DOS overwrites parts of the interrupt vectors for interrupts 1 to 3. The solution to the problem is to either upgrade to DOS 3.3 or to copy the disk parameter vector to 70:0F37 before running or at the start of your program. ┌─────────────────────────────────────────────────────────────────────────────┐ │Interrupt 1Fh Ptr to Graphics Character Extensions (Graphics Set 2) 3**18 │ └─────────────────────────────────────────────────────────────────────────────┘ (0:007Ch) This is the pointer to data used by the ROM video routines to display characters above ASCII 127 while in CGA medium and high res graphics modes. note 1) Doubleword address points to 1K table composed of 28 8-byte character definition bit-patterns. First byte of each entry is top row, last byte is bottom row. 2) The first 128 character patterns are located in system ROM. 3) This vector is set to 000:0 at system initialization. 4) Used by DOS' external GRAFTABL command.