Hello all, I've run into another weird problem that doesn't make sense.

While debugging some code with a Signum Systems emulator I have run into a problem that has been making me go back to the data sheets for answers--answers that I haven't been able to find. I have seen several times Timer 0, running in mode 1 (16 bit timer), where upon rollover from FFFF to 0000 TF0 was *not* set, so my timer ISR never executed (or executed 64K clocks later than expected).

My reading of the book says that TF0 should set, regardless of the state of the interrupt system or its interrupt enable ET0. Yesterday I had seen the problem happen most often when rollover occured just as I reached a piece of code where EA was reset (momentarily); this morning first thing I saw it happen again in regular code.

Any ideas on what would prevent TF0 from setting? Based on past experience, I've got to be doing something wrong...

Thanks for any input!

Dennis