Missed INT0 Interrupt?

Started by Unknown April 11, 2003
Has anyone seen a case where the '5416 could miss an interrupt? I'm
grasping at straws here I know.

I've got this SPI interface that uses a couple of interrupt lines to
control the flow of the data, and it works most of the time :> But
after running for a bit (seconds to a minute or so) somethnig happens
and it stops.

Examining my state machine indicates that it totally missed an ack
interrupt from the slave processor. In the INT0 interrupt I'm
incrementing a counter that is checked and decremented in
non-interrupt time (surrounded by INTM=1/INTM=0 even though I don't
think a *(var) -= #1 needs interrupt protection because its a single
instruction, right?

Looking at the data on a scope (Tek 458, not great for this) I see SPI
clocks and an ack, so the slave, as far as I can tell, really is
pulling the line low (for about 1uS, more than long enough for the

The DSP has a variety of things happening, mostly DMA interrupts going

I really doubt the DSP could be missing the irq, but it sure looks
that way!

Does this ring any bells with anyone?



Brian C. Lane (W7BCL) Programmer RF, DSP & Microcontroller Design