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The C Users' Group Library 1994 August
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wc-cdrom-cusersgrouplibrary-1994-08.iso
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vol_100
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169_01
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casync.asm
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Assembly Source File
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1984-07-29
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11KB
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425 lines
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
*** COPIED 01/25/84 04:31:17 BY KSC ***