Don't read the port. Just set the "pin" in portbuf, then copy it out to the
port. 

As long as you ALWAYS set the pin in portbuf FIRST, you will never loose
anything by not reading the port.

--
James.

-----Original Message-----
From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf Of
Martin
Sent: Friday, January 25, 2008 11:35
To: Microcontroller discussion list - Public.
Subject: [PIC] macros to get around read-modify-write

Do you use macros in your assembly program to get around the fact that 
you shouldn't be using read-modify-write commands on a port?
I wrote two macros that should accomplish this:

setb    macro    port, pin
    movff    port,portbuf
    bsf        portbuf, pin
    movff    portbuf, port
    endm


clrb    macro    port, pin
    movff    port,portbuf
    bcf        portbuf, pin
    movff    portbuf, port
    endm

Simple, right? They don't work right. If I do this:

setb PORTB,0
setb PORTB,1
nop
clrb PORTB,0
clrb PORTB,1

Pin 0 is set then goes low while pin 1 goes high, then pin 1 goes low - 
so it looks like the second "setb" doesn't occur until pin 0 is cleared. 
The pulses don't overlap at all.
Do you know what the problem is?
-
Martin
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