Toggling pins on/off in PASM

Philldapill

How do you toggle a pin on and off in PASM? Is there an equivalent of OUTA[noparse]/noparse in PASM?

Timmoore

translate pins to pin masks then use

or outa, mask
andn outa,mask

Coley

mov     dira,#1  
mov     outa,#1

Turns on P0

Use it with a pin mask to turn on a specific pin eg outa, #1 <<16 would turn on P16

Regards,

Coley

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Post Edited (Coley) : 6/30/2008 11:51:41 PM GMT

Philldapill

Perfect. Thanks guys!

Phil Pilgrim (PhiPi)

Coley said...
Use it with a pin mask to turn on a specific pin eg outa, #1 <<16 would turn on P16

Actually, it would not. Immediate operands are limited to values between 0 and $1ff, so 1 << 16 is out of range. But you can still use indirect addressing:

        or      dira,mask16    'Set pin as an output.
        or      outa,mask16    'Turn pin on.
        andn    outa,mask16    'Turn pin off.
        xor     outa,mask16    'Toggle pin.

mask16  long    1 << 16

-Phil

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Post Edited (Phil Pilgrim (PhiPi)) : 6/30/2008 11:36:04 PM GMT

Philldapill

haha, that's funny you posted this Phil. I was just trying that and would get an error saying the source must be less than $1FF. I was just about to post an "er?" question. Thanks!

Timmoore

The other thing to be careful with using mov for outa, is if the cog has more than 1 output pin, the mov outa affects them all, i.e. the others are set to 0. Its great if thats what you want but often you only want to affect 1 pin.

Coley

DAT

Led        mov     _mask,#1              
           shl      _mask,#16
           mov     dira,_mask
           mov     outa,_mask

_mask      res      1 

Oops, my bad!

This does work though!

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Philldapill

Well, I'm excited. My first ever PASM program! yay!

org
entry   or dira, pinOut
        mov time, cnt
        add time, duty
        mov invduty, period
        sub invduty, duty         
        jmp #:loop

:loop   waitcnt time, invduty
        or outa, pinOut
        waitcnt time, duty
        xor outa, pinOut
        jmp #:loop                     'loop for next cycle  
 
period  long  8000
duty    long  7000
invduty res 1                     
time    res 1
value   res 1
t1      res 1
pinOut  long 1<<15
ctraval res 1

·

Timmoore

res must be the last thing. pinout needs to be moved earlier.

Philldapill

Oops! You're right. Fixed it.

Now I have a question... If I set the period to 80,000, the frequency should be 1kHz, right? No. My meter says it's ~166Hz... pretty off if you ask me...

Philldapill

Ok, so now the question is, how do you use an "if this, then do that" statement in PASM?

I need to see some incremental count has reached a threshold, then do something else.

Timmoore

Look at tjz, tjnz for 0 and non-0, djnz, test and cmp instructions
you test and cmp you need to specify to set wz or wc
then you can use
cmp t0,#4 wz
if_z jmp #equal4

it compares t0 to 4 sets the wz flag if they are the same.
if_z says execute the instruction if the wz flag is set, so you would execute the jmp otherwise its a nop

you can set the flags on most instructions and you can use if_z etc on most instructions, so for example

cmp t0,#4 wz
if_z mov t0, #0

would set t0 to 0 if it was 4
I would take a look through fullduplexserial, its a pretty good straightforward piece of pasm that is complex enough to show a lot of stuff. (I would not look at my version of fullduplexserial4fc, I was trying to push the prop and so it re-writes the code on the fly - not just source/dest addresses but the instructions, etc. Once you get used to pasm take a look at some of the stuff you can do if you really want but it does make the code a lot harder for anyone to understand)