title IBM PC Communications I/O Routines -- Curt Klinsing pgroup group prog prog segment byte public 'prog' ; ;A set of Lattice C callable functions to support ;interrupt driven character I/O on the IBM PC. Input ;is buffered, output is polled. ; public init_comm ;initialize the comm port, public uninit_comm ;remove initialization, public set_xoff ;enable/disable XON/XOFF, public get_xoff ;read XON/XOFF state, public rcvd_xoff ;returns true if XOFF rcvd, public sent_xoff ;true if XOFF sent, public inp_cnt ;returns count of rcv chars, public inp_char ;get one char from buffer, public inp_flush ;flush input buffer, public outp_char ;output a character, ; ;A better description can be found in the comment ;block in each function. ; assume cs:pgroup ; FALSE EQU 0 TRUE EQU NOT FALSE ; BASE EQU 03F8H ;BASE FOR SERIAL BOARD ; LCR equ BASE+3 ; Line control register IER equ BASE+1 ; Interrup Enable Register MCR EQU BASE+4 ;modem control register EnblDRdy equ 01H ; enable 'data-ready' interrupt bit IntCtlr EQU 21H ;OCW 1 FOR 8259 CONTROLLER EnblIRQ4 EQU 0EFH ;Enable COMMUNICATIONS (IRQ4) DATAPORT EQU BASE ;transmit/receive data port MaskIRQ4 EQU 10H ;BIT TO DISABLE COMM INTERRUPT (IRQ4) MDMSTA EQU BASE+5 ;line status register MDMMSR EQU BASE+6 ;modem status register MDMBAD EQU BASE ;lsb baud resgister MDMBD1 EQU BASE+1 ;msb baud rate register MDMCD EQU 80H ;mask for carrier dectect SETBAU EQU 80H ;code for Divisor Latch Access Bit MDMTBE EQU 20H ;8250 tbe flag MDMBRK EQU 40H ;command code for 8250 break LINMOD EQU 03H ;line mode=8 bit, no parity MDMMOD EQU 0BH ;modem mode = DTR and RTS HIGH STOP2 EQU 04H ;BIT FOR TWO STOP BITS IF BAUD<300 RS8259 EQU 20H ;OCW 3 FOR 8259 RSTINT EQU 64H ;SPECIFIC EOI FOR COMM INTERRUPT XOFF EQU 13H ;XOFF character XON EQU 11H ;XON character ; ; MISCELLANEOUS EQUATES ; CR EQU 13 LF EQU 10 DosCall EQU 33 ;INTERRUPT NUMBER FOR DOS CALL CNSTAT EQU 11 ;FUNCTION NUMBER FOR CONSOLE STATUS CNIN EQU 1 ;FUNCTION NUMBER FOR CONSOLE INPUT BUFSIZ EQU 512 ;Max NUMBER OF CHARS SetIntVect EQU 25H ;SET INTERRUPT VECTOR FUNCTION NUMBER ; ; DUMP BUFFER, COUNT AND POINTER. ; CIRC_BUF DB BUFSIZ DUP(?) ;ALLOW 512 MaxIMUM BUFFERED CHARACTERS BUF_TOP EQU $ - 1 ;KEEP TRACK OF THE TOP OF THE BUFFER CIRC_TOP DW BUF_TOP ; ; CIRC_IN DW OFFSET CIRC_BUF ;POINTER TO LAST CHAR. PLACED IN BUFFER CIRC_CUR DW OFFSET CIRC_BUF ;POINTER TO NEXT CHAR. TO BE RETRIEVED FROM ; BUFFER CIRC_CT DW 0 ;COUNT OF CHARACTERS USED IN BUFFER SNT_XOFF DB FALSE ;FLAG TO CHECK IF AN XOFF HAS BEEN SEND GOT_XOFF DB FALSE ;FLAG TO CHECK IF AN XOFF HAS BEEN RECEIVED SEE_XOFF DB FALSE ;FLAT TO SEE IF WE ARE INTERESTED IN XON/XOFF ; ; ; ;set_xoff(flag) Enable (flag != 0) or disable ;int flag; (flag == 0) XON/ XOFF protocol ; for the character input stream. ;If enabled, an XOFF will be sent when the buffer ;reaches 3/4 full. NOTE: an XON will not be sent auto- ;matically. Your program must do it when it sees ;the rcvd_xoff() flag, and ready for more chars. ; set_xoff proc near push bp PUSH DS ;SAVE DATA SEGMENT mov bx,[bp+6] push cs pop ds ; move code seg addr to data seg reg. cmp bx,0 jnz to_on mov see_xoff,FALSE jmp done1 to_on: mov see_xoff,TRUE done1: pop ds pop bp ret set_xoff endp ; ;flag= get_xoff() Returns the current setting ; of the XON/ XOFF flag set ;by set_xoff(), above. ; get_xoff proc near push bp push ds ; save data reg push cs pop ds ; move code seg addr to data seg reg. xor ax,ax mov al,see_xoff pop ds pop bp ret get_xoff endp ; ;flag= sent_xoff(); Returns true if an XOFF ; character was sent, indicating ;the receive buffer is 3/4 full. ; sent_xoff proc near push bp push ds ; save data reg push cs pop ds ; move code seg addr to data seg reg. xor ax,ax mov al,snt_xoff pop ds pop bp ret sent_xoff endp ; ;rcvd_xoff() Returns true if an XOFF was ; received; will return false as ;soon as an XON is received. Does not effect data output, ;only indicates the above. (Obviously useless for binary ;data.) ; rcvd_xoff proc near push bp push ds ; save data reg push cs pop ds ; move code seg addr to data seg reg. xor ax,ax mov al,got_xoff pop ds ; restore data reg pop bp ret rcvd_xoff endp ; ;count= inp_cnt() Returns the number of characters ; available in the input buffer. ; inp_cnt proc near push bp push ds ; save data segment push cs pop ds ; move code seg addr to data seg reg mov ax,circ_ct pop ds pop bp ret inp_cnt endp ; ;inp_flush() Flush the input buffer. ; inp_flush proc near push bp push ds ; save data reg push cs pop ds ; move code seg addr to data seg reg. mov bx,offset circ_buf mov circ_in,bx mov circ_cur,bx xor ax,ax mov circ_ct,ax pop ds pop bp ret inp_flush endp ; --------- Init ----------------------------------- ; Program initialization: ; -- Set up vector for RS232 interrupt (0CH) ; -- Enbl IRQ4 ; -- Enbl RS232 interrupt on data ready ; ; --------------------------------------------------- init_comm proc near push bp cli ; ---- Set up INT x'0C' for IRQ4 push ds push cs pop ds ;cs to ds mov dx,offset IntHdlr ;relative adddres of interrupt handler mov al,0cH ;interrupt number for comm. mov ah,SetIntVect ;function number for setting int vector int DosCall ;set interrupt in 8086 table pop ds ;restore DS ; ---- Enbl IRQ4 on 8259 interrupt controller cli in al,IntCtlr ; get current masks and al,EnblIRQ4 ; Reset IRQ4 mask out IntCtlr,al ; And restore to IMR ; --- Enbl 8250 data ready interrupt mov dx,LCR ; DX ==> LCR in al,dx ; Reset DLAB for IER access and al,7FH out dx,al mov dx,IER ; Interrupt Enbl Register mov al,EnblDRdy ; Enable 'data-ready' interrupt out dx,al ; --- Enbl OUT2 on 8250 mov dx,MCR ; modem control register mov al,08H ; Enable OUT2 out dx,al sti pop bp ret init_comm endp ; ;uninit_comm() Removes the interrupt structure ; installed by init_comm(). Must be ;done before passing control to the DOS, else chars received ;will be stored into the next program loaded! ; uninit_comm proc near push bp ; --- Disable IRQ4 on 8259 cli in al,IntCtlr ;GET OCW1 FROM 8259 or al,MaskIRQ4 ;DISABLE COMMUNICATIONS INTERRUPT out IntCtlr,al ; --- Disable 8250 data ready interrupt mov dx,LCR ; DX ==> LCR in al,dx ; Reset DLAB for IER access and al,7FH out dx,al mov dx,IER ; Interrupt Enbl Register mov al,0 ; Disable all 8250 interrupts out dx,al ; --- Disable OUT2 on 8250 mov dx,MCR ; modem control register mov al,0 ; Disable OUT2 out dx,al sti pop bp ret uninit_comm endp ; ;char inp_char() Return a character from the input ; buffer. Assumes you have called ;inp_cnt() to see if theres any characters to get. ; inp_char proc near push bp push ds ; save data reg push cs pop ds ; move code seg addr to data seg reg. mov bx,circ_cur xor ax,ax mov al,[bx] ;get next char from circ_buf DEC circ_ct ;decrement circ_buf COUNT CMP bx,circ_top ;ARE WE AT THE TOP OF THE circ_buf? JZ reset_cur ;JUMP IF SO INC bx ;ELSE, BUMP PTR JMP SHORT upd_cur reset_cur: mov bx,OFFSET circ_buf ;RESET circ_in TO BOTTOM OF BUF. upd_cur: mov circ_cur,bx ;SAVE NEW PTR xor cx,cx mov cl,see_xoff ;check if interested in xon/xoff cmp cl,TRUE jnz clnup2 ;not interested, so goto return cmp snt_xoff,TRUE ;have we sent an xoff? jnz clnup2 ;no, so return cmp circ_ct,80h ;yes, so see in buf is now emptying jg clnup2 ;not empty enuf to send xon, jump to ret mov snt_xoff,FALSE mov cl,XON push ax ; save char call comout pop ax clnup2: pop DS ;GET BACK ENTERING DS pop bp ret inp_char endp ; ;outp_char(c) Output the character to the ;char c; serial port. This is not buffered ; or interrupt driven. ; outp_char proc near push bp mov bp,sp mov cl,[bp+4] sti call comout pop bp ret outp_char endp ; ;Local subroutine: output CL to the port. ; comout: mov dx,MDMSTA in al,dx ; get 8250 status and al,MDMTBE ; check for transmitter ready jz comout ; jump if not to wait mov al,cl ; get char to al mov dx,DATAPORT out dx,al ; output char to 8251 ret ; ; RECEIVE INTERRUPT HANDLER (CHANGED TO PLACE CHARACTERS IN A ; CIRCULAR circ_buf AND TO SEND AN XOFF IF THE circ_buf IS MORE THAN ; 3/4 FULL - S.G.) ; IntHdlr: CLI push cx push dx push bx push ax push ds mov ax,cs ;get cur code segment mov ds,ax ; and set it as data segment mov bx,circ_in ;GET circ_buf IN PTR mov DX,DATAPORT ;GET DATA PORT NUMBER IN AL,DX ;GET RECEIVED CHARACTER ; push ax ; push dx ; xor ax,ax ; xor dx,dx ; mov dl,al ; mov ah,2 ; int DosCall ; pop dx ; pop ax xor cx,cx mov cl,see_xoff ;check if interested in xon/xoff cmp cl,TRUE jnz ck_full ;not interested goto ck if buf full mov cl,al ;put char in cl for testing and cl,7fh ;turn off any parity bits cmp cl,XOFF ;see if we got an xoff jnz ck_xon mov got_Xoff,TRUE ; code for handling xon/xoff from remote jmp clnup ck_xon: cmp cl,XON jnz reg_ch mov got_Xoff,FALSE jmp clnup ; ;Normal character; not XON/XOFF, or XON/XOFF disabled. ; reg_ch: test snt_Xoff,TRUE ;SEE IF sentXoff IS SET jnz ck_full ;IF SO, DON'T SEND ANOTHER XOFF CMP circ_ct,(BUFSIZ * 3)/4 ;ALLOW BUF TO BECOME 3/4 FULL BEFORE ; SENDING XOFF jb savch ;IF IT'S OK, CONTINUE push ax ;SAVE CHARACTER mov CL,XOFF ;GET XOFF CHARACTER mov snt_Xoff,TRUE ;RESET sentXoff call comout ; AND SEND IT pop ax ;RETRIEVE CHARACTER JMP SHORT savch ;IF WE'RE HERE, THE circ_buf HAS BUFSIZ-80H ; CHARACTERS ck_full: CMP circ_ct,BUFSIZ ;SEE IF circ_buf ALREADY FULL JZ clnup ; JUMP IF SO, DO NOT PLACE CHARACTER IN BFR savch: mov [bx],AL ;SAVE NEW CHARACTER IN circ_buf inc circ_ct ;BUMP circ_buf COUNT CMP bx,circ_top ;ARE WE AT THE TOP OF THE circ_buf? JZ reset_in ;JUMP IF SO inc bx ;ELSE, BUMP PTR JMP SHORT into_buf reset_in: mov bx,OFFSET circ_buf ;RESET circ_in TO BOTTOM OF BUF. into_buf: mov circ_in,bx ;SAVE NEW PTR clnup: mov AL,RSTINT OUT RS8259,AL ;ISSUE SPECIFIC EOI FOR 8259 pop ds ;GET BACK ENTERING DS pop ax pop bx pop dx pop cx sti iret ; prog ends end ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;