Hello Craig,

Have you made any changes to the code? Perhaps added an interrupt that might be pulling it out? If you have made some changes please post your code, it might be somewhat easier than guessing...

Just to test something, try replacing
Code:
TXWait:
  if nirq = 1 then
      goto TXWait
  endif
with "pause 100" or something like that.

Also, check with a meter or scope that nIrq actually goes low.

Best Regards,
Paul