Simple boot-up code for an Atmel A91

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I'm still having an extremely hard time getting IRQ interrupts of any
sort to work on my AT91R40008.
Does anyone have a simple boot.s that sets up all the stacks for IRQ
interrupts and then can branch to C functions?
I am not using any debug monitors like Angel.
I am not using any pre-canned libraries (like Atmel's)
I am using gcc-3.2, and I am trying to implement my interrupt handlers
in C also.

Here is exactly what I'm trying to do:
- I'm not bothering with running from flash at the moment. Currently
I"m locating my code at 0x00, manually initiating a REMAP through my
JTAG interface and then loading the code (so it should be all loaded
into RAM)
- I have a small test program which toggles PIO pins every TIMER0
overflow interrupt.

The problems I've been having:
- The pin will go high (suggesting the reception of 1 interrupt) and
then stay high - halting the processor results in the PC being at
either Data Abort or Program Abort in the vector table (the first
weirdness).
- If I issue a RESET command, and then execute the program again (w/o
powering down the chip), the program runs fine and just loops
infinitely on my while(1) { } at the end of main, but there is no pin
toggling at all (suggesting no reception of interrupts)

I have been communicating with Tauno somewhat and he has been a great
help so far.

Here's what I understand I must do (but may not be implementing it
correctly):
Setup the IRQ, SVC, and SYS stacks.
Enable Timer interrupts in the TC registers and the AIC (pretty sure I
have this correct).
Setup interrupt vector in the AIC (pretty sure I also have this
correct).
Writing to AIC_EOICR at the end of the interrupt handler (I have this
correct).

Re: Simple boot-up code for an Atmel A91
Go to the Atmel website and find the AT91 library AT91LibV214_light.zip or
the non-light version.  It's about a 9 MB download. In it find a Cstartup.s
file.  There are more than one, pick the one appropriate for your chip.  It
should have what you need and plenty of other example code.

Scott


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Re: Simple boot-up code for an Atmel A91

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we had a similar problem and the fix was to write 0, 8 times to the end
of interrupt register to make sure that all the queued interrupts have
been removed ~ do this as the last part of an initialisation process.
This efectively flushes all pending interrupts otherwise the whole
process gets out of kilter and problems ensue...


Re: Simple boot-up code for an Atmel A91

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James, remember to read the timer status register before EOI in the
interrupt service, to reset the internal request.

Tauno Voipio
tauno voipio @ iki fi



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