need help with PASM

TimH

This is my first attempt at PASM with the propeller. I've studied various examples in this forum but have hit a wall.
I want to monitor a pin (15) for a pulse - (high). When detected I want to output another pulse after a delay on pin 16.
The output section works fine if I comment the 3 lines after :loop.
I'm sure its a simple error but I cannot see it.

jazzed

TimH said...
... The output section works fine if I comment the 3 lines after :loop.
I'm sure its a simple error but I cannot see it.

Try this:

:loop
                mov       read_port, ina                 'look for a pulse on Key In (15). If not then keep
                test      read_port,pinmask_in  wz       'looking else continue with output key.
                tjz       read_port,#:loop               'Mask all but pin 15 - loop if zero (no key in)

You could also use this to the same effect:

:loop
                waitpeq   pinmask_in, pinmask_in         'look for a pulse on Key In (15). If not then keep

Another variation:

:loop
                test     pinmask_in,ina  wz              'look for a pulse on Key In (15). If not then keep looking else continue with output key.
                tjz       read_port,#:loop               'Mask all but pin 15 - loop if zero (no key in)

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
--Steve

Propeller Tools

• Propalyzer: Propeller PC Logic Analyzer
• BMA: An on-chip PASM Debugger
• SPUD: Spin Source Level Debugger

Post Edited (jazzed) : 9/3/2009 3:30:00 AM GMT

TimH

Thanks Steve

The first change did not work but the 2nd did.

I need to go back to the manual and try to figure out why.

jazzed

Maybe the pulse is too fast for the loop. Assuming 80MHz operation, the first one takes 150ns, the test
alternative I added last takes 100ns, waitpeq detects smaller pulses .... How much smaller? Don't remember.

Glad you have something working.

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
--Steve

Propeller Tools

• Propalyzer: Propeller PC Logic Analyzer
• BMA: An on-chip PASM Debugger
• SPUD: Spin Source Level Debugger

Beau Schwabe

TimH,

In your original code change...

read_port         long

...so that it reads...

read_port         long      0

... and that will solve your error.
The way it is, pinmask_key is assigned to the read_port value and gets overwritten when you change read_port which corrupts the pinmask_key value.

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Beau Schwabe

IC Layout Engineer
Parallax, Inc.

Post Edited (Beau Schwabe (Parallax)) : 9/3/2009 4:29:09 AM GMT

jazzed

Ouch! read_port and pinmask_key are the same address without the added 0.

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
--Steve

Propeller Tools

• Propalyzer: Propeller PC Logic Analyzer
• BMA: An on-chip PASM Debugger
• SPUD: Spin Source Level Debugger

TimH

Steve & Beau

Thanks for your help - there's certainly plenty of scope for errors with PASM. I'm sure once you've spend a few hours tracking a problem its not easily forgotten though.

Tim