Category : Dbase (Clipper, FoxBase, etc) Languages Source Code
Archive   : DB-COMM.ZIP
Filename : INPORT.ASM

page 66, 120
title DBASE III+ Com Port Handler V1.0
subttl By Carl R. Weber

IF1
%out Pass 1
ENDIF
IF2
%out Pass 2
ENDIF

;
;====================================
;
; Get a string of characters from the com port
; terminated by a Carriage Return or the end of string
; The number of characters received is the length of the
; Dbase III+ string passed.
; A single character may be obtained if this routine is called
; with a string whose length is one.
;
; return ffh if no carrier
; return feh if activity timeout
; else characters received with parity stripped
;
; By C.R. Weber
; 6256 Golden Coin Court
; Columbia, MD 21045
;
; 8/8/86
;
;======================================

; default comm port to use

comline equ 0000h ;com 1


; time out defaults

carr_time equ 30 ;time to wait for carrier
;20 seconds now
no_act_time equ 600 ;no activity timeout
;7 min

rs232_port equ 0000h ;offset to port addresses at segment 40h



cseg segment
assume cs:cseg


inport proc far ;call this with dbase

push si ;save registers
push dx
push cx
push bx
push ax

mov dx, comline ;set up for com line

cmp bx, 0 ;check for valid string passed
jz eloop ;no data if zero

mov cs:beg_buf, bx ;save begining of buffer
;in cs relative storage

start label near

cmp byte ptr [bx],0 ;end of original dbase string?
jz short eloop ;yes then return


nextch label near

call short chin ;get character from modem
or al, al ;was it a timeout or loss of carrier
js opps ;yes

cmp al, 13 ;CR?
jnz short nocr


strend label near

mov byte ptr [bx], 0 ;Yes then terminate the string
jmp short eloop ;and return to dbase


nocr label near

cmp al, 8 ;back space?
jnz short nobs
call short erase ;erase the character
jmp short nextch ;get next character


nobs label near

cmp al, 7fh ;DELETE?
jnz short svchr
call short erase ;erase the character
jmp short nextch ;get next char


svchr label near

mov byte ptr [bx], al ;save character
inc bx ;point to next location
call short chout ;echo it back
jmp short start


opps label near

mov bx, cs:beg_buf ;get begining of str
mov byte ptr [bx], al ;save error code as first character
inc bx ;so dbase can find it
jmp short strend ;and ret to dbase


eloop label near

pop ax ;restore registers
pop bx
pop cx
pop dx
pop si
ret ;far return to dbase


inport endp

; temp storage for local vars

beg_buf dw 0 ;beg of dbase string buffer
t_cnt dw 0 ;inactivity timeout count
car_cnt dw 0 ;no carrier timeount count


;======================================
; get character from com port
;
; return ffh if no carrier
; return feh if activity timeout
; else character received with parity stripped
;======================================


chin proc near

push ds
mov ax, 40h ;set up data segment for RS232 port
mov ds, ax ;address

mov ax, no_act_time ;sec to wait for no activity
mov cs:t_cnt, ax
mov ax, carr_time ;sec to wait for carrier detect
mov cs:car_cnt, ax

mov si, comline ;get comline index
shl si, 1 ;make word offset
mov dx, rs232_port[si] ;get address of port

add dx, 4 ;control reg
mov al, 1
out dx, al ;set DTR

add dx, 2 ;modem status reg


carr_loop label near

mov ah, 80h ;Data carrier detect
call wait_st ;wait for DCD
jz car_ok ;timed out no carrier

mov ax, cs:car_cnt
dec ax
mov cs:car_cnt, ax
jnz carr_loop
pop ds
mov al, 0ffh ;no carrier
ret


car_ok label near

dec dx ;line status register


ch_loop label near

mov ah, 1 ;recv char?
call wait_st ;wait for character
jz ch_rdy ;got one ?

mov ax, cs:t_cnt ;no - then check count
dec ax
mov cs:t_cnt, ax
jnz ch_loop ;more time
pop ds ;else return error as
mov al, 0feh ;just timeout
ret


ch_rdy label near

mov dx, rs232_port[si] ;get address of port
in al, dx ;get char
and al, 07fh ;strip parity anyway
pop ds
ret


chin endp


;======================================
; send out character in al
;======================================


chout proc near

push dx
mov ah, 1
mov dx, comline
int 14h
pop dx
ret

chout endp


;======================================
; erase prev character typed
;======================================


erase proc near

push ax
cmp bx, cs:beg_buf ;make sure that there are characters
jle short era1 ;first character
dec bx ;move pointer back
mov al, 8 ;delete char on user's
call short chout ;screen
mov al, ' ' ;with space
call short chout
mov al, 8 ;
call short chout


era1 label near

pop ax
ret
erase endp


;======================================
; wait for a status in port [dx] and bit pattern in ah
;
;======================================


wait_st proc near

push cx
xor cx, cx ;set up loop count


w1 label near

in al, dx ;get stat
and al, ah ;strip unwanted bits
cmp al, ah ;check for all set
je w_end ;yes?
loop w1 ;loop again

or ah, ah ;zero flag off - error


w_end label near

pop cx
ret

wait_st endp


cseg ends
end