Category : C Source Code
Archive   : MNP14.ZIP
Filename : SETPAR.ASM

title mnpc\setpar.asm
page 60,132
;==============================================================================
;
; The Microcom MNP Library
; (Microsoft C Version)
;
;------------------------------------------------------------------------------
;
; Setpar - set input data byte to specified character format
;
; Synopsis: c = setpar(data_byte, par_type);
;
; char data_byte;
; int par_type;
;
;==============================================================================

_data segment word public 'DATA'
_data ends
dgroup group _data

_text segment byte public 'CODE'
assume cs:_text,ds:dgroup

public _setpar

; Local equates
NONE = 0
EVENP = 1
ODD = 2
MARK = 3
SPACE = 4
;
_setpar proc near
push bp ;save register
mov bp,sp ;point to parameters

mov ah,[bp+6] ;get parity type
mov al,[bp+4] ;get data byte

cmp ah,NONE ;8 none?
je setp9 ;yes-go exit

and al,07fh ;clear parity bit

cmp ah,EVENP ;7 even?
jne setp1 ;no-go on

or al,al ;get current parity sense
jpe setp9 ;if even, go exit
or al,80h ;else set parity bit
jmp short setp9 ;and go exit

setp1:
cmp ah,ODD ;7 odd?
jne setp2 ;no-go on

or al,al ;get current parity sense
jpo setp9 ;if odd, go exit
or al,80h ;else set parity bit
jmp short setp9 ;and go exit

setp2:
cmp ah,MARK ;7 mark?
jne setp9 ;no-already set to space, go exit

or al,80h ;set parity bit

setp9:
xor ah,ah ;clear high part of ax
pop bp ;restore register
ret ;return byte in ax

_setpar endp

_text ends
end