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Assembly Source File | 1987-06-04 | 13.7 KB | 520 lines

page 60,132 title SERIAL C interrupt driven serial I/O routines for IBM PC COM ports ;These routines allow c programs to use serial port 0 in an interrupt ;driven environment. This environment is locally generated and controlled ; ;This program is released to the public domain for non-commercial ;uses. Please do not charge "copying fees" when redistrubiting ;this program. Feedback is desired. ; ;Skip Hansen, WB6YMH 6/22/86 ;RCP/M (213) 541-2503 ;or via RLI linked systems at WB6KAJ or KD6SQ ; ; 1/84 Greg Lindberg Original routines written for Pronto Computer ; ; 2/86 Skip,WB6YMH Modified for use on IBM PC COM1 ; ; 4/26/86 Lee, WB6KAJ Modified transmit byte routine to check ; CTS before sending a byte for use with ; hardware flow control. ; ; 01/30/87 Mike, WA6FXT Modified to conform to Microsoft 'C' 4.0 ; Also added DTR control to _serinit, _serldone ; ; 01/31/87 Mike, WA6FXT Modified to allow COM port selection to be ; done dynamic (command option). ; ; 6/1/87 Skip, WB6YMH Corrected bug in serldone. Fixed bug in ; serlbaud caused by fallthru logic after ; port option was added to serlinit. ; ; ; ;macro for output from al to 16 bit port adr ; outbyte macro name mov dx,name ;point dx to port adr out dx,al ;output 8 bit value endm ; ;macro for byte input to al from 16 bit port ; inbyte macro name mov dx,name ;point dx to port adr in al,dx ;read byte endm ; ;macro for output from al to 16 bit port base adr with offset 'name' ; outport macro name mov dx,name ;get the offset value call out_byte ;output the byte endm ; ;macro for byte input to al from 16 bit port base adr with offset 'name' ; inport macro name mov ax,port_base ;get the base address add ax,name ;add the OFFSET mov dx,ax ;set DX to point at port address in al,dx ;read byte endm false equ 0 true equ not false i8259_mask equ 21h ;interrupt mask register i8259_ctrl equ 20h ;interrupt controller control port rdaien equ 1 ;enable bit for RDA interrupts linmod equ 03h ;line mode, 8 bits, no parity mdmmod equ 0bh ;modem mode= DTR and RTS high & ; COM port definitions COM1 equ 3f8h ;base address of COM1 8250 com_vec1 equ 0ch ;interrupt vector for COM1 int_level1 equ 4 ;interrupt level on 8259 int_mask1 equ 00010000b ;interrupt mask bit in 8259 COM2 equ 2f8h ;base address of COM2 8250 com_vec2 equ 0bh ;interrupt vector for COM2 int_level2 equ 3 ;interrupt level on 8259 int_mask2 equ 00001000b ;interrupt mask bit in 8259 ; OFFSETS from base address of COM port mdmdat equ 0 ;offset to data port mdmint equ 1 ;interrupt enable register mdmlin equ 3 ;line control register mdmmdm equ 4 ;modem control register mdmsta equ 5 ;line status register mdmmsr equ 6 ;modem status register DTR_BIT equ 1 ;DTR control bit in modem control reg RTS_BIT equ 2 ;RTS control bit check_cts equ true _TEXT SEGMENT BYTE PUBLIC 'CODE' _TEXT ENDS _DATA SEGMENT WORD PUBLIC 'DATA' _DATA ENDS CONST SEGMENT WORD PUBLIC 'CONST' CONST ENDS _BBS SEGMENT WORD PUBLIC 'BBS' _BBS ENDS DGROUP GROUP CONST, _BBS, _DATA ASSUME CS:_TEXT, DS:DGROUP, SS:DGROUP _DATA SEGMENT public trnbuffin,trnbuffout,trn_buff,trn_buff_end public rcvbuffin,rcvbuffout,rcv_buff,rcv_buff_end public com_port,port_base ; DATA AREA trnbuffin dw offset DGROUP:trn_buff ;pointer to input point in transmit buffer trnbuffout dw offset DGROUP:trn_buff ;pointer to output point in transmit buffer trn_buff db 160 dup (?) ;transmit buffer trn_buff_end equ $ rcvbuffin dw offset DGROUP:rcv_buff ;pointer to input point in receive buffer rcvbuffout dw offset DGROUP:rcv_buff ;pointer to output point in receive buffer rcv_buff dw 2048 dup (?) ;receive buffer rcv_buff_end equ $ dw 100 dup (?) ;local interrupt stack intstk equ $ ssseg dw ? ;storage for interrupted stack seg spptr dw ? ;storage for interrupted stack pointer com_port dw ? ;storage for COM port selection port_base dw ? ;storage for COM port base address _DATA ENDS _TEXT SEGMENT PUBLIC _SERLINIT,_TRNBYTE,_RCVBYTE,_SERLDONE PUBLIC _TIMERCV,_PURGERCV,_SERLBAUD,_rcvint PUBLIC _dtr_on,_dtr_off,rts_on,rts_off dsseg dw $ ;storage for C data segment ; ; name serlbaud -- baud rate initialazation for serial port 0 ; ; synopsis serlbaud(,port_num,baud); ; int port_num; port number (IE: 0=COM1) ; int baud; baud rate for serial port ; ; description This routine initializes serial port 0 at the specified ; baud rate. ; _serlbaud proc near push bp ;save BP mov bp,sp ;point to passed parms mov dx,[bp+4] ;get port number mov al,[bp+6] ;get requested baud rate ror al,1 ;put in right place ror al,1 ror al,1 and al,0e0h ;save only baud rate or al,3 ;get rest of int 14h command xor ah,ah ;make it init command int 14h ;init port 0 for 8 data bits, 1 stop, no parity mov ax,[bp+4] ;get port number push ax ; call _serlinit ; pop ax ;fix stack pop bp ;restore callers BP ret ;all done so fall thru to serlinit() ;since ibm clears interrupt setup with ;int 14 baudrate calls _serlbaud endp ; ; name serlinit -- interrupt driven serial initialization ; ; synopsis serlinit(port_num); ; int port_num; port number (IE: 0=COM1) ; ; description This routine initializes interrupts for serial port 0. ; _serlinit proc near push bp ;save BP mov bp,sp ;point to passed parms push ds ;save data segment mov dsseg,ds ;save C data segment for interrupt routine mov ax,[bp+4] ;get the port number mov com_port,ax ;set the number for later use mov dx,COM1 ;assume COM1 cmp ax,0 ;see if COM1 jz ser_setcom mov dx,COM2 ;set for COM2 ser_setcom: mov port_base,dx ;set the port base address mov ax,com_port ;get the port number mov bx,2500h+com_vec1 ;assume COM1 cmp ax,0 ;COM1? jz ser_setvec ;yes mov bx,2500h+com_vec2 ;must be COM2 ser_setvec: mov ax,cs ;set up for init of interrupt vector mov ds,ax mov dx,offset cs:_rcvint ;point to isr mov ax,bx ;move the vector to AX cli ;no interrupts now int 21h ;initialize receive interrupt pop ds ;restore data pointer mov ax,offset ds:trn_buff ;clear transmit buffer mov trnbuffin,ax mov trnbuffout,ax mov ax,offset ds:rcv_buff ;clear receive buffer mov rcvbuffin,ax mov rcvbuffout,ax inport mdmdat ;clear any garbarge characters in al,dx ;from COM port in al,dx ; mov al,linmod ;clear DLAB bit and set line mode outport mdmlin ; mov al,mdmmod ;get mode to use outport mdmmdm ;to modem control register mov al,rdaien ;enable interrupts from RDA outport mdmint ; mov dx,i8259_mask ;unmask interrupts from serial port 0 in al,dx ;get present mask push ax ;save it mov ax,com_port ; check the port cmp ax,0 ;see if COM1 jnz ser_mask2 ;must be COM2 pop ax ;restore AX and al,not int_mask1 ;enable interrupts for COM1 jmp short ser_setmask ser_mask2: pop ax ;restore AX and al,not int_mask2 ;enable interrupts for COM2 ser_setmask: out dx,al ;restore new mask call _dtr_on ;allow inputs sti ;interrupts back on pop bp ;restore callers BP ret ;all done so exit _serlinit endp ; ; name trnbyte -- transmit byte of data over serial port 0 ; ; synopsis trnbyte(trndata); ; int trnbyte; ;data byte to send ; ; description This routine sends a byte of data out serial port 0. ; _trnbyte proc near push bp ;save BP mov bp,sp ;point to passed parms trn_byte_loop: inport mdmsta ;get status byte and al,20h ;transmit buffer empty ? jz trn_byte_loop ;loop if not if check_cts inport mdmmsr ;get modem status reg. and al,10h ;look at cts. jz trn_byte_loop ;loop until ready. endif mov al,[bp+4] ;get character to output outport mdmdat ;send character pop bp ;restore callers BP ret ;all done so exit _trnbyte endp ; ; name rcvbyte -- receive byte from serial port 0 ; ; synopsis rcvbyte(); ; ; description This routine attempts to return a byte of data from ; serial channel 0. If no data is available it returns ; 0ffffh else it returns the data with error status in ; the high byte ; _rcvbyte proc near mov bx,rcvbuffout ;is buffer empty cmp bx,rcvbuffin mov ax,0ffffh ;load false return je short rcvend ;if so go try leave mov ax,[bx] ;get return byte inc bx ;update pointer inc bx cmp bx,offset ds:rcv_buff_end jl rcvoutsav mov bx,offset ds:rcv_buff rcvoutsav: mov rcvbuffout,bx rcvend: ret ;all done so exit _rcvbyte endp _rcvint proc far push ds ;save present data seg mov ds,dsseg ;set to C data segment mov ssseg,ss ;save interrupted stack mov spptr,sp mov ss,dsseg ;point to local stack mov sp,offset ds:intstk push ax ;save everything push bx ; push dx ; inport mdmdat ;get received char mov bl,al ;save char inport mdmsta ;get status and al,0eh ;save only framing, and overrun error mov ah,al ;put status into high byte mov al,bl ;get char back mov bx,rcvbuffin ;is buffer full inc bx inc bx cmp bx,offset ds:rcv_buff_end jl rcvint1 mov bx,offset ds:rcv_buff rcvint1: cmp bx,rcvbuffout je short rcvintdn ;if so leave mov bx,rcvbuffin mov [bx],ax ;else save char and error status inc bx ;update pointer inc bx cmp bx,offset ds:rcv_buff_end jl rcvint2 mov bx,offset ds:rcv_buff rcvint2: mov rcvbuffin,bx rcvintdn: mov ax,com_port ;check which COM port cmp ax,0 ;COM1? jnz rcv_com2 ;no MOV AL,60h+int_level1 ;specific EOI, level 1 jmp short rcv_int_clr rcv_com2: MOV AL,60h+int_level2 ;specific EOI, level 1 rcv_int_clr: outbyte i8259_ctrl ;send specific EOI to 8259 rcv_int_dn: pop dx ;restore everything pop bx ; pop ax ; mov ss,ssseg ;restore interrupted stack mov sp,spptr pop ds ;restore data seg iret ;and leave _rcvint endp ; ; name timercv -- receive with time out ; ; synopsis timercv(timeout); ; int timeout; ;time out in seconds ; ; description This routine tries to receive a char within a given ; time. If a char becomes available it is returned. ; Else if passed time elapses it returns -1 as an error. ; _timercv proc near push bp ;save BP mov bp,sp ;point to passed parms sub sp,4 ;make local storage mov ax,[bp+4] ;get time to wait mov cx,182 ;find time in ticks mul cx mov cx,10 div cx mov [bp-4],ax ;save it xor ax,ax ;find out current time in ticks int 1ah add [bp-4],dx ;make it ending time adc cx,0 mov [bp-2],cx ;and save it timrlp: call _rcvbyte ;is there a character ready cmp ax,0ffffh jne timrend ;leave if so xor ax,ax ;else get new time int 1ah sub dx,[bp-4] ;timed out yet sbb cx,[bp-2] jl timrlp ;if not go back and check again mov ax,0ffffh ;else error out timrend: add sp,4 ;deallocate local storage pop bp ;restore callers BP ret ;all done so exit _timercv endp ; ; name purgercv -- purge receiver ; ; synopsis purgercv(); ; ; description This routine keeps requesting receive characters ; until the timercv times out for one second. ; _purgercv proc near mov ax,1 ;time out of one second push ax ; purgelp: call _timercv ;see if there are any chars cmp ax,0ffffh ;did it time out jne purgelp ;try again if not pop bx ;clean stack ret ;done leave _purgercv endp ; ; name serldone -- disables interrupts from serial port 0 ; ; synopsis serldone(); ; ; description This routine turns off interrupts from serial port 0 ; and restores the interrupt vectors to there default valuse ; _serldone proc near push bp ;save BP mov bp,sp ;point to passed parms call _dtr_off ;disable the port inbyte i8259_mask ;mask out interrupts from serial port push ax ;save it mov ax,com_port ; check the port cmp ax,0 ;see if COM1 jnz serd_mask2 ;must be COM2 pop ax ;restore AX or al,int_mask1 ;disable interrupts for COM1 jmp short serd_clrmask serd_mask2: pop ax ;restore AX or al,int_mask2 ;disable interrupts for COM2 serd_clrmask: out dx,al ;restore new mask pop bp ;restore callers BP ret ;all done so exit _serldone endp ; ; name dtr_on -- turn on DTR handshaking line on RS-233 port ; ; synopsis dtr_on(); ; _dtr_on proc near mov al,linmod ;clear DLAB bit and set line mode outport mdmlin ; inport mdmmdm ;get current setup or al,DTR_BIT ;turn DTR on outport mdmmdm ;to modem control register ret _dtr_on endp ; ; name dtr_off -- turn on DTR handshaking line off RS-233 port ; ; synopsis dtr_off(); ; _dtr_off proc near mov al,linmod ;clear DLAB bit and set line mode outport mdmlin ; inport mdmmdm ;get current setup and al,not DTR_BIT ;DTR off outport mdmmdm ;to modem control register ret _dtr_off endp ; ; name rts_on -- turn on RTS handshaking line on RS-233 port ; ; synopsis rts_on(); ; rts_on: mov al,linmod ;clear DLAB bit and set line mode outport mdmlin ; inport mdmmdm ;get current setup or al,RTS_BIT ;turn RTS on outport mdmmdm ;to modem control register ret ; ; name rts_off -- turn on RTS handshaking line off RS-233 port ; ; synopsis rts_off(); ; rts_off: mov al,linmod ;clear DLAB bit and set line mode outport mdmlin ; inport mdmmdm ;get current setup and al,not RTS_BIT ;RTS off outport mdmmdm ;to modem control register ret ; ; A routine to output a byte in al, to the port @ port_base, offset ; by the value in dx ; out_byte: push ax ;save the byte to send mov ax,port_base ;get the base address add ax,dx ;add the OFFSET mov dx,ax ;set DX to point at port address pop ax ;restore AX out dx,al ;output 8 bit value ret _TEXT ENDS end