Setting a timeout for WAITATN - can't get it to work

bob_g4bby · 2021-05-10 20:24

In assembler, using WAITATN by itself works fine - but I don't like using it because it will wait forever if ATN isn't set.

This code doesn't work for me, though, for WAITATN with a timeout

getct xx                           ' read the bottom half of the 64 bit system counter
add a,xx                         ' add in the required timeout in ticks
setq a                             ' timeout set for when the system counter = a
waitatn wc                     ' wait for atn flag then clear it and reset carry, else set carry if no ATN happens

The loop this is part of no longer loops when I set ATN for the cog it's running in. What am I doing wrong? (If this code appears a bit weird, it's because it's the assembler in Taqoz)

Has anyone got WAITATN with a timeout to work, please? If so, please show me your equivalent code fragment

Thanks, Bob

cgracey · 2021-05-10 20:52

Maybe you are corrupting 'a'. How about this, instead:

  getct   xx
  add     xx,a
  setq    xx
  waitatn wc

bob_g4bby · 2021-05-11 13:26

Chip, thanks for the suggestion, that wasn't it. I got it to go perfectly, and my WAITATN word in TAQOZ looks like this:-

--- The cog waits for the ATN flag for up to 'clocks' ticks. 
--- If ATN occurs before timeout, 'flag' = 1, else if timedout, 'flag' = 0
code WAITATN                ( clocks -- flag ) 
        getct xx            ' read the bottom half of the 64 bit system counter
        add a,xx
        setq a              ' timeout set for when the system counter = a
        waitatn wc          ' wait for atn flag
if_nc   mov a,#1        ' ATN flag detected
if_c        mov a,#0        ' we timed out
        ret
end

I'll post a complete demo on one of the TAQOZ threads

cgracey · 2021-05-11 14:10

Bob, there is an instruction which gets C or !C into a register. You can replace the last three lines with:

  _RET_  WRNC    a

bob_g4bby · 2021-05-11 15:47

Thanks Chip, the instruction set is unfamiliar just yet. That fft you did a while back was compact. I hope to adapt it to process an IQ signal stream for software radio, with other dsp blocks in assembly, glued together with Taqoz. I have a feeling that WAITATN will come in very handy, syncing the cogs that do the signal processing. There's plenty of scope for parallelism.

Setting a timeout for WAITATN - can't get it to work

Comments