Hi,
I am attempting to use the AVR Studio IDE to implement a simple program for ATtiny2313, utilizing both the 8-bit timer0 and the 16-bit timer1. I am using the latest version of AVR Studio (4.11.401). Unfortunately, I have discovered that the output compare interrupt for timer1 is not handled correctly by the simulator.
Here is what I did:
- Create a new project under AVR Studio, and select "Simulator" as the platform, and "ATtiny2313" as the device.
- Write a short program to intialize timer1. * Set the timer to CTC mode, and set the TOP value to OCR1A (WGM13:10==0100) * Set OCR1A to 5 * Enable the output compare A interrupt in TIMSK (OCIE1A==1) * Write an interrupt handler routine for it, with a simple NOP inside, and place it at the correct address in the interrupt vector table (* Write a short program to intialize timer1. * Set the timer to CTC mode, and set the TOP value to OCR1A (WGM13:10==0100) * Set OCR1A to 5 * Enable the output compare A interrupt in TIMSK (OCIE1A==1) * Write an interrupt handler routine for it, with a simple NOP inside, and place it at the correct address in the interrupt vector table ($0004)04)
- My main program enables global interrupts, and loops in an infinite loop.
Here is what I observe in the simulator:
- All the timer registers (TIMSK, OCR1A, TCCR1x) are set correctly
- The timer counter TCNT1H:TCNT1L counts from 0 to 5, then clears back to 0, as expected (in CTC mode)
- The flag OCF1A in TIFR is set each time the timer loops around. The OCF1A flag is cleared during the next CPU instruction.
- And yet, my interrupt routine is never called.
I have tried setting breakpoints in my routine, using the "run to cursor" command, or stepping through execution manually with the "step into" button. The result is the same: the output compare A interrupt flag is set and cleared, yet my interrupt routine is never called.
Just out of curiosity, I decided to replace "attiny2313" with "at90s2313" as the Device under the "Debug | Select platform and device" menu in AVR studio. When I did that, my interrupt routine started working as expected -- i.e., it was called each time the OCF1A flag was set.
It would appear that there is a bug in the simulator for attiny2313, which prevents it from simulating the OCF1A interrupt properly.
I should also point out that the 8-bit timer0 does not suffer from this problem - - both its output compare interrupts (OCF0A and OCF0B) are raised and simulated properly.
Is anyone else experiencing this problem ? Is there a workaround ?