I'm having an issue trying to use RFVAR from within a debug interrupt service routine.
The fifo pointer address set with RDFAST is lost on entry to the ISR.
It seems that the fifo pointer address is being replaced with $FFFC8 + cogid << 2.
These values I can confirm with a GETPTR instruction.
Here's some test code for P123-A9 to show the issue.
If you change the "test_cog" value you will see the values mentioned above.
If the debug interrupt is dusabled the value counts from $f00 ok.
sys_clk = 60_000_000
test_cog = 0
wrlong isr,##$FFFC0 + test_cog << 2 'comment out to disable debug
isr jmp #\my_isr
mycode bmask dirb,#15
rdfast #0,##$f00 'set fifo start address to $f00
again rfbyte pa 'dummy byte read
getptr outb 'leds <= fifo address
my_isr setbrk #1
Am I breaking the rules again? :)