Stumped

[Mike Pitts]

Does anyone know what triggers the IRQ interrupt in P4 PCM's?  

I've deciphered most of the loops in my PCM and how they are 
scheduled (which is quite interesting BTW).  But there's some 
code that's in the IRQ vector, but I can't figure out what 
triggers the IRQ.  I assume it's tied to some external line, 
but which one?

TIA,
-Mike
"Reverse engineering a 64k PCM is like eating an elephant, 
one byte at a time."