Category : Assembly Language Source Code
Archive   : KEYCOMM.ZIP
Filename : KEYCOMM.ASM

; Source code for KEYCOMM.ASM



; This is a modified version of a very simple comm program from
; NRI. The original was made up of a bunch of subroutines that were called
; one after another. I just converted it so that there are no call instructions
; or returns, except for the interupt service routine.
; Trilobyte user #151
; Electric Dreams BBS
; 1-414-654-9159
; or
;Duane Saaski
;Exec pc




mov ah,09h
mov dx,offset hello
int 21h ;print hello message
jmp start
old_seg dw 00
old_off dw 00
buf_ptr dw 00
dis_ptr dw 00
buf_end dw 0ffh
start: mov ah,35h
mov al,0ch
int 21h ;get com1 interupt vector
mov old_seg,es
mov old_off,bx
mov dx,offset com
mov ah,25h
mov al,0ch
int 21h ;store new com1 interupt vector
mov dx,03f9h
mov al,1
out dx,al ;select type of com1 interupt
in al,21h
and al,not 10h
out 21h,al ;program interupt chip
push ds ;save old data segment
mov ds,cs
mov al,0bh
mov dx,03fc ;modem control
out dx,al
mov al,80h
mov dx,03fbh
out dx,al ;divisor access
mov al,60h
mov dx,03f8h
out dx,al ;set baud rate
inc dx
mov al,00
out dx,al
mov dx,03fbh
mov al,3
out dx,al ;set line parameters
display: mov bx,dis_ptr
cmp bx,buf_ptr ;jump to key polling if
jz key ;there is no new char in buffer
mov al,[buffer+bx] ;get character from buffer
inc bx ;increment dis_ptr in bx
cmp bx,buf_end ;see if at end of buffer
jne roomy2
xor bx,bx ;set dis_ptr to 0
roomy2: mov dis_ptr,bx
mov ah,0eh
mov bh,0
int 10h ;output teletype character
key: mov dx,03fdh
in al,dx ;check if transmit hold reg. is empty
test al,20h
jz display ;if full goto display
mov ah,6
mov dl,0ffh
int 21h ;keyboard input
jz display ;if no character,leave
cmp al,01bh ;check for escape
jz exit
mov dx,03f8h
out dx,al ;output to com1
jmp display
com: sti ;start of interupt service
push ax,bx,dx,ds
push cs
pop ds
mov dx,03f8h ;get character on-line
in al,dx
cli
mov bx,buf_ptr ;get buffer pointer
mov [buffer+bx],al ;stick character in buffer
inc bx ;increment buffer pointer
cmp bx,buf_end ;see if at end of buffer
jne roomy1 ;if not goto roomy1
xor bx,bx ;if so, set buf_ptr to zero
roomy1: mov buf_ptr,bx ;save buf_ptr
sti ;turn interupts on
mov al,20h ;end of interupt
out 20h,al ;instruction
pop ds,dx,bx,ax
iret
exit: pop ds ;get ds back
mov ah,9
mov dx,offset bye_msg
int 21h ;print goodbye message
mov al,0
mov dx,03f9h ;turn off 8250 interupts
out dx,al
in al,21h ;turn off com1 in interupt chip
or al,10h
out 21h,al
push ds
mov dx,old_off ; -------
mov ds,old_seg ; ^
mov ah,25h ; |
mov al,0ch ; |
int 21h ;replace interupt vector
pop ds
mov ah,4ch
mov al,0
int 21h ;program end
bye_msg: db 'Program terminated.',13,10,'$'
hello: db 'Com1--1200-8-N-1 hit esc key to exit.',13,10,'$'
buffer db 256 dup(0)