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Assembly Source File | 1986-06-19 | 22.4 KB | 878 lines

name asynch page 55,132 title 'ASYNCH --- asynchronous driver' .lfcond ; ; Asynchronous Port Driver (COM1 or COM2) ; version 1.0 April 16, 1985 ; ; Copyright (C) 1985 Ray Duncan ; ; To assemble, link, and convert this program into ; a BIN file, follow these steps: ; ; C>MASM ASYNCH; ; C>LINK ASYNCH; ; C>EXE2BIN ASYNCH.EXE ASYNCH.BIN ; C>DEL ASYNCH.EXE ; ; Ignore the message "Warning: no stack segment" from the Linker. ; ; Then add the line: ; ; DEVICE=ASYNCH.BIN ; ; to your CONFIG.SYS file. ; code segment public 'CODE' driver proc far assume cs:code,ds:code,es:code org 0 comm_port equ 0 ;0=COM1, <>0=COM2 if comm_port ;define physical port assignments ; COM2 port assignments comm_irqm equ 08h ; Mask for IRQ3 comm_int equ 0bh comm_data equ 02f8h comm_ier equ 02f9h comm_lcr equ 02fbh comm_mcr equ 02fch comm_stat equ 02fdh else ; COM1 port assignments comm_irqm equ 10h ; Mask for IRQ4 comm_int equ 0ch comm_data equ 03f8h comm_ier equ 03f9h comm_lcr equ 03fbh comm_mcr equ 03fch comm_stat equ 03fdh endif Max_Cmd equ 15 ; MS-DOS command code maximum In_Len equ 2048 ; length of ring buffer for reads Out_Len equ 2048 ; length of ring buffer for writes cr equ 0dh ; ASCII carriage return lf equ 0ah ; ASCII line feed eom equ '$' ; end of message signal page ; ; Device Driver Header ; Header dd -1 ;link to next device,-1= end of list dw 8000h ;attribute word ;bit 15=1 for character devices dw Strat ;device "Strategy" entry point dw Intr ;device "Intrrupt" entry point db 'ASYNCH1 ' ;char device name, 8 char, or ;if block device, no. of units ;in first byte followed by ;7 don't care bytes ; ; local variables for use by driver ; Rq_Ptr dd ? ; pointer to request header ; passed to Strat by BDOS Ident db cr,lf,lf db 'LMI Asynchronous Port Driver 1.0' db cr,lf db 'Copyright (c) 1985 ' db 'Laboratory Microsystems Inc.' db cr,lf,lf,eom rcv_in dw 0 ; input ptr to read ring buffer rcv_out dw 0 ; output ptr to read ring buffer xmt_in dw 0 ; input ptr to write ring buffer xmt_out dw 0 ; output ptr to write ring buffer page ; ; MS-DOS Command Codes dispatch table ; The "Intr" routine uses this table and the Command Code ; supplied in the Request Header to transfer to the ; appropriate driver subroutine. Dispatch: dw Init ; 0 = init driver into system dw Media_Chk ; 1 = media check on blk dev dw Build_Bpb ; 2 = build BIOS param block dw Ioctl_Inp ; 3 = I/O ctrl read from dev dw Input ; 4 = normal destructive read dw Nd_Input ; 5 = non-destructive read,no wait dw Inp_Stat ; 6 = return current input status dw Inp_Flush ; 7 = flush device input buffers dw Output ; 8 = normal output to device dw Outp_Vfy ; 9 = output with verify dw Outp_Stat ; 10 = return current output status dw Outp_Flush ; 11 = flush output buffers dw Ioctl_Outp ; 12 = I/O control output dw Dev_Open ; 13 = device open (MS-DOS 3.x) dw Dev_Close ; 14 = device close (MS-DOS 3.x) dw Rem_Media ; 15 = removeable media (MS-DOS 3.x) page ; ; MS-DOS Request Header structure definition ; Request struc ; request header template structure Rlength db ? ; length of request header Unit db ? ; unit number for this request Command db ? ; request header's command code Status dw ? ; driver's return status word Reserve db 8 dup (?) ; reserved area Media db ? ; media descriptor byte Address dd ? ; memory address for transfer Count dw ? ; byte/sector count value Sector dw ? ; starting sector value Request ends ; end of request header template ; ; Status word is interpreted as follows: ; ; Bit(s) Significance ; 15 Error ; 10-14 Reserved ; 9 Busy ; 8 Done ; 0-7 Error code if bit 15=1 ; Predefined BDOS error codes are: ; ; 0 Write protect violation ; 1 Unknown unit ; 2 Drive not ready ; 3 Unknown command ; 4 CRC error ; 5 Bad drive request structure length ; 6 Seek error ; 7 Unknown media ; 8 Sector not found ; 9 Printer out of paper ; 10 Write fault ; 11 Read fault ; 12 General failure ; 13-14 Reserved ; 15 Invalid disk change (MS-DOS 3.x) page ; ; Media descriptor byte is interpreted as follows ; if Non-IBM-Format bit is zero ; ; Bit(s) Significance ; 3-7 always set ; 2 1=removeable 0=not removeable ; 1 1=8 sector 0=not 8 sector ; 0 1=2 sided 0=not 2 sided ; ; Current valid DOS descriptor bytes, 5 1/4" disks ; 0F9H 2 sided 15 sector ; 0FCH 1 sided 9 sector ; 0FDH 2 sided 9 sector ; 0FEH 1 sided 8 sector ; 0FFH 2 sided 8 sector ; ; 0F8H (fixed disk) page ; ; this is the hardware interrupt handler for ; Asynch Communications Adaptor ; Svc_Int proc far ;interrupt service routine ;for asynch controller sti ;turn interrupts back on push ax ;save all necessary registers push bx push dx push ds mov ax,cs ;make local data addressable mov ds,ax call Recv ;receive a character cli ;disable interrupts ;for clean exit mov al,20h ;send EOI to 8259 out 20h,al pop ds ;restore all registers pop dx pop bx pop ax iret ;and exit handler Svc_Int endp page ; ; This is the input interrupt driver. ; Check for RDA status on interrupt, ; if RDA = True then input character ; Called on each interrupt. ; Recv proc near ;assumes CS = DS mov dx,comm_stat ;read status in al,dx and al,1 ;RDA ? jz Recv2 ;no, jump mov dx,comm_data in al,dx ;read this character cli ;clear interrupts for ;pointer manipulation mov bx,rcv_in ;get buffer pointer ;store this character mov byte ptr [In_Buf+bx],al inc bx ;bump pointer cmp bx,In_Len ;time for wrap? jne Recv1 ;no,jump xor bx,bx ;yes,reset pointer Recv1: mov rcv_in,bx ;store back updated pointer sti ;unmask interrupts Recv2: ret Recv endp page ; ; This is the interrupt output driver. ; Check for TBE status on interrupt, if TBE = True ; then transmit another character if any waiting. ; Called by Command Codes 8 & 9 to start I/O, ; and will be called on interrupt in final version. ; Xmit proc near ;assumes CS = DS mov dx,comm_stat ;read status in al,dx and al,20h ;TBE? jz Xmit9 ;no, jump mov bx,xmt_out ;any characters waiting cmp bx,xmt_in ;in output buffer? je Xmit9 ;no, jump mov al,[bx+Out_Buf] ;yes, get next char inc bx cmp bx,Out_Len ;time to wrap? jne Xmit1 ;no xor bx,bx ;yes,reset ring buffer ptr Xmit1: mov xmt_out,bx ;store updated pointer mov dx,comm_data ;transmit this char. out dx,al Xmit9: ret Xmit endp page ; Device Driver "Strategy Routine" ; Each time a request is made for this device, the BDOS ; first calls "Strategy routine", then immediately calls ; the "Interrupt routine". ; The Strategy routine is passed the address of the ; Request Header in ES:BX, which it saves in a local ; variable and then returns to BDOS. Strat proc far ; save address of Request Header mov word ptr cs:[Rq_Ptr],bx mov word ptr cs:[Rq_Ptr+2],es ret ; back to BDOS Strat endp page ; Device Driver "Interrupt Routine" ; This entry point is called by the BDOS immediately after ; the call to the "Strategy Routine", which saved the long ; address of the Request Header in the local variable "Rq_Ptr". ; The "Interrupt Routine" uses the Command Code passed in ; the Request Header to transfer to the appropriate device ; handling routine. Each command code routine is responsible ; for any necessary return information into the Request Header, ; then transfers to Error or Exit to set the Return Status code. Intr proc far push ax ; save general registers push bx push cx push dx push ds push es push di push si push bp push cs ; make local data addressable pop ds les di,[Rq_Ptr] ; ES:DI = Request Header ; get BX = Command Code mov bl,es:[di.Command] xor bh,bh cmp bx,Max_Cmd ; make sure its legal jg Unk_Command ; too big, exit with error code shl bx,1 ; form index to Dispatch table ; and branch to driver routine jmp word ptr [bx+Dispatch] page ; General collection of exit points for the driver routines. Unk_Command: ; Come here if Command Code > 12 mov al,3 ; Sets "Unknown Command" error ; code and "Done" bit. Error: ; Transfer here with AL = error code. mov ah,81h ; Sets "Error" and "Done" bits. jmp Exit Done: mov ah,1 ; Come here if I/O complete and ; no error, sets "Done" bit only. Exit: ; General purpose exit point. ; Transfer here with AX = ; Return Status word to be ; placed into Request Header. lds bx,cs:[Rq_Ptr] ; set status mov ds:[bx.Status],ax pop bp ;restore general registers pop si pop di pop es pop ds pop dx pop cx pop bx pop ax ret ; back to BDOS page ; MS-DOS Command Code # 1 Media Check ; Block devices only. Should be a NOP for character devices. ; ; This routine is called first by BDOS for a block device transfer, ; passing current media descriptor byte at Request Header + ; ; Media Check routine sets status word and in addition passes back ; return byte at Request Header + 14 as follows: ; -1 Media has been changed ; 0 Don't know if media changed ; 1 Media has not been changed ; ; If driver can return 1 or -1, performance is improved because ; MS-DOS does not need to reread the FAT for each directory access. Media_Chk: jmp Done page ; ; MS-DOS Command Code # 2 Build BIOS Parameter Block ; ; Block devices only. Should be a NOP for character devices. ; ; This routine is called by MS-DOS when Media-Changed code is ; returned by Media Check routine, or if Not Sure code is returned ; and there are no dirty buffers. ; ; Build BPB call receives pointer to one-sector buffer in Address ; Field of Request Header (offset 14). If "Non-IBM-Format" bit ; in attribute word is zero, the buffer contains the first sector ; of the FAT including the media identification byte and should not ; be altered by the driver. If the "Non-IBM-Format" bit is set, ; the buffer may be used as scratch space. ; ; The Build BPB routine sets status and returns a DWORD pointer to ; the new Bios Parameter Block at Request Header + 18. ; Build_Bpb: jmp Done page ; ; MS-DOS Command Code # 3 I/O Control Read from device ; ; Only called if IOCTL bit set in Device Header Attribute word. ; ; Called with: ; ; Request Header + 13 BYTE Media descriptor byte from DPB ; Request Header + 14 DWORD Transfer address ; Request Header + 18 WORD byte/sector count ; Request Header + 20 WORD starting sector no. (block dev.) ; ; Returns the Return Status word set appropriately, and ; Request Header + 18 WORD actual bytes or sectors transferred ; ; No error check is performed on IOCTL I/O calls. Ioctl_Inp: jmp Done page ; ; MS-DOS Command Code # 4 Read from device ; ; Called with ; ; Request Header + 13 BYTE Media descriptor byte from DPB ; Request Header + 14 DWORD Transfer address ; Request Header + 18 WORD byte/sector count ; Request Header + 20 WORD starting sector no. (block dev.) ; ; Returns the Return Status word set appropriately, and ; Request Header + 18 WORD actual bytes or sectors transferred Input: mov si,rcv_out ;receive buffer output pointer cmp si,rcv_in ;compare to buffer input ptr jne Input1 ;something is in buffer ;set characters xfer'd = 0 mov word ptr es:[di.Count],0 jmp Done ;go set Done flag Input1: xor dx,dx ;set chars xferd count=0 ;get requested transfer count mov cx,word ptr es:[di.Count] ;given DS:SI = addr input buffer ;set ES:DI = addr user's buffer push word ptr es:[di.Address] push word ptr es:[di.Address+2] pop es pop di Input2: ;transfer one character mov al,byte ptr ds:[si+In_Buf] mov byte ptr es:[di],al inc si inc di inc dx ;count characters given to user cmp si,In_Len ;buffer pointer wrap? jne Input3 ;no xor si,si ;yes Input3: cmp si,rcv_in ;input buffer exhausted? je Input4 ;yes, user got all he can get cmp dx,cx ;user got max requested? jne Input2 ;not yet Input4: mov rcv_out,si ;update buffer out pointer les di,cs:[Rq_Ptr] ;let ES:DI = Request Header ;store length actually transferred mov word ptr es:[di.Count],dx jmp Done ;go set Done & No Error flags page ; ; MS-DOS Command Code # 5 Non-destructive Read from Device ; ; Character devices only. ; ; If Input Status request returns Busy bit=0 (characters ; waiting), the next character that would be read is returned ; at Request Header + 13. This character is not removed from ; the Input Buffer. This basically provides the capability to ; "look-ahead" by one character. Nd_Input: mov bx,rcv_out cmp bx,rcv_in je Nd_Input1 ;jump, nothing in buffer ;something in read buffer, ;fetch first waiting char mov al,byte ptr [bx+In_Buf] jmp Nd_Input2 Nd_Input1: ;nothing in read buffer, mov al,0 ;return a null character Nd_Input2: ;put char into Request Header mov byte ptr es:[di+13],al jmp done ;set Done status, no error page ; ; MS-DOS Command Code # 6 Return current device input status ; ; Character devices only. ; ; Sets the Returned Status word: ; Done bit = 1 ; Busy bit = 1 read request would go to physical device ; = 0 characters already in device buffer, read request ; would return quickly. ; ; MS-DOS assumes all character devices have type-ahead buffer. ; If device does not have type-ahead buffer, should always ; return Busy bit=0 so MS-DOS will not hang. Inp_Stat: mov ax,rcv_in ;anything in read buffer? cmp ax,rcv_out je Inp_Stat1 ;no,jump jmp Done ;yes, let busy bit=0 Inp_Stat1: mov ax,300h ;request goes to device jmp Exit ;so let busy bit=1 page ; ; MS-DOS Command Code # 7 Flush device input buffers ; ; Character devices only. ; ; Terminate all pending requests, i.e. the Input buffer is ; emptied. Inp_Flush: cli ; block interrupts mov rcv_in,0 ; reset buffer pointers mov rcv_out,0 sti ; restore interrupts jmp Done page ; ; MS-DOS Command Code # 8 Write to device ; ; Called with ; ; Request Header + 13 BYTE Media descriptor byte from DPB ; Request Header + 14 DWORD Transfer address ; Request Header + 18 WORD byte/sector count ; Request Header + 20 WORD starting sector no. (block dev.) ; ; Returns the Return Status word set appropriately, and ; Request Header + 18 WORD actual bytes or sectors transferred Output: ;DS:SI = user's data address mov si,word ptr es:[di.Address] mov ds,word ptr es:[di.Address+2] ;CX = length of user's data mov cx,word ptr es:[di.Count] jcxz Output3 ;exit if length=0 mov di,cs:xmt_in ;ES:DI = output buffer address push cs pop es Output1: mov al,byte ptr ds:[si] mov byte ptr es:[di+Out_Buf],al inc si inc di cmp di,Out_Len ;buffer pointer wrap? jne Output2 ;no xor di,di ;reset output buffer pointer Output2: loop Output1 ;loop until all string moved mov cs:xmt_in,di ;store updated buffer input ptr Output3: mov ax,cs ;make buffers addressable for mov ds,ax ;XMIT routine, Output4: mov ax,xmt_in cmp ax,xmt_out je Output5 call Xmit ;transmit one character jmp Output4 Output5: jmp Done ;go set Done & No Error flags page ; ; MS-DOS Command Code # 9 Write with verify to device ; ; Called with ; ; Request Header + 13 BYTE Media descriptor byte from DPB ; Request Header + 14 DWORD Transfer address ; Request Header + 18 WORD byte/sector count ; Request Header + 20 WORD starting sector no. (block dev.) ; ; Returns the Return Status word set appropriately, and ; Request Header + 18 WORD actual bytes or sectors transferred Outp_Vfy: jmp Output page ; ; MS-DOS Command Code # 10 Return device output status ; ; Character devices only. ; ; Sets the Returned Status word: ; Done bit = 1 ; Busy bit = 1 write request would wait for completion of ; current request ; = 0 device idle, write request would start immediately. ; Outp_Stat: ; always return Not Busy for now ; *** later should return Busy if ; transmit buffer is full *** jmp Done page ; ; MS-DOS Command Code # 11 Flush output buffers ; ; Character devices only. ; ; Terminate pending requests. The output buffer is emptied. Outp_Flush: cli ; block interrupts mov xmt_in,0 ; reset buffer pointers mov xmt_out,0 sti ; re-enable interrupts jmp Done page ; ; MS-DOS Command Code # 12 I/O Control write to device ; ; Only called if IOCTL bit in Device Header Attribute word is set. ; ; Called with ; ; Request Header + 13 BYTE Media descriptor byte from DPB ; Request Header + 14 DWORD Transfer address ; Request Header + 18 WORD byte/sector count ; Request Header + 20 WORD starting sector no. (block dev.) ; ; Returns the Return Status word set appropriately, and ; Request Header + 18 WORD actual bytes or sectors transferred ; ; No error check is performed on IOCTL calls. Ioctl_Outp: jmp Done page ; ; MS-DOS Command Code # 13 Device Open ; ; MS-DOS version 3.0 and above only. ; Only called if OPEN/CLOSE/RM bit set in Attribute word. ; May be used to manage local buffering. Reference count ; is incremented keeping track of number of open files on ; the device. On character devices can be used to send ; device initialization string, which can be set by IOCTL ; Write. Note that CON AUX and PRN devices are always open. ; ; Returns the Return Status word set to "Done. ; Dev_Open: jmp Done page ; ; MS-DOS Command Code # 14 Device Close ; ; MS-DOS version 3.0 and above only. ; Only called if OPEN/CLOSE/RM bit set in Attribute word. ; May be used to manage local buffering. Reference count ; is decremented keeping track of number of open files on ; the device; when count reaches zero all files have been closed ; and the driver should flush buffers as user may change disks. ; On character devices can be used to send device post-I/O ; string such as a form feed, which can be set by IOCTL ; Write. Note that CON AUX and PRN devices are never closed. ; ; Returns the Return Status word set to "Done". ; Dev_Close: jmp Done page ; ; MS-DOS Command Code # 15 Removeable Media ; ; MS-DOS version 3.0 and above only. ; Only called if OPEN/CLOSE/RM bit set in Attribute word ; and device type is block. ; ; Returns the Return Status word set to "Done" and ; Busy bit = 1 if media is non-removable. ; = 0 if media is removable. ; Rem_Media: jmp Error page ; This initialization code for the driver is called only ; once when the driver is loaded. It returns its own ; address to the DOS as the start of free memory after the ; driver, so that the memory occupied by INIT will be ; reclaimed after it is finished with its work. If it ; is a block device driver it must also return the address of ; the Bios Parameter Block pointer array; if all units are the ; same all pointers can point to the same BPB. ; ; Only MS-DOS services 01-0CH and 30H can be called ; by the INIT code. ; ; Called with: ; ; Request Header + 18 DWORD pointer to the character after the "=" ; on the CONFIG.SYS line that loaded ; driver; this information is read only. ; 22 BYTE drive letter for first unit of a ; block driver (0=A 1=B etc) ; ; Returns: ; ; Request Header + 13 BYTE Number of units (block devices only) ; + 14 DWORD address of first free memory above driver ; + 18 DWORD BPB pointer array (block devices only) ; Init: ; MS-DOS Command Code # 0 ; initialize device driver push es ; push Request Header addr push di mov ah,9 ; print sign-on message mov dx,offset Ident int 21h pop di ; restore Request Header addr pop es ; set addr of interrupt handler push ds xor ax,ax mov ds,ax mov bx,comm_int*4 mov word ptr [bx],offset Svc_Int mov word ptr [bx+2],cs pop ds mov dx,comm_lcr ;make sure DLAB is off in al,dx and al,07fh out dx,al mov dx,comm_mcr ;modem controller DTR, RTS, mov al,0bh ;and OUT2 to enable interrupts. out dx,al mov dx,comm_ier ;enable interrupts for TBE mov al,1 ;and RDA on asynch controller. out dx,al in al,21h ;8259 int mask register ;Reset IRQ3 or IRQ4 mask and al,not comm_irqm out 21h,al ; set first usable memory addr. mov word ptr es:[di.Address],offset End_Buf mov word ptr es:[di.Address+2],cs jmp Done Intr endp Driver endp In_Buf db In_Len dup (?) Out_Buf db Out_Len dup (?) End_Buf equ $ code ends end