Instruction fetch exception on C674

Marcos Doblado

Other Parts Discussed in Thread: OMAPL138

Hello,

I'm working with the omapL138 making a signal processing algorithm in the C674x part of this ic.

I have a part of the code written in asm to get the highest speed as possible. The problem is that sometimes I get an instruction fetch exception coming from a repetitive part of the code. It is the direction of the first instruction where a branch instruction jumps to close the loop. I have read in the CPU and instruction set document (page 665) that this error can come from one of the next situations:

But I'm not able to understand what is happening. I have a similar code running on C6678 cpu and works fine.

What can be happening?

Regards (and merry xmas)

over 14 years ago

0 Paul.Yin over 14 years ago

TI__Genius 14405 points

Marcos,

Please read this post: http://e2e.ti.com/support/development_tools/code_composer_studio/f/81/t/97831.aspx

and let me know if Brad's comments helps.

regards,

Paul

0 Brad Griffis over 14 years ago

TI__Guru*** 125430 points

I'm not surprised to hear you're having this kind of issue. It's extremely difficult to write assembly code for c6000. An easy fix is to disable interrupts in your function, e.g. add a few instructions to disable interrupts at the beginning and then restore (not enable) interrupts at the end. The only downside of this solution is increased interrupt latency. You would probably have to rewrite the function otherwise.

0 Marcos Doblado over 14 years ago in reply to Brad Griffis

Intellectual 455 points

I disabled the maskable interrupts and it works fine.

Have you got any idea to solve the problem?, not just hide it. If I don't get any new solution I will let it this way, but the asm code takes a lot of time so, as you said, the interruption latency will grow and I'm not sure if it will be a problem in the future.

Thanks.

0 Brad Griffis over 14 years ago in reply to Marcos Doblado

TI__Guru*** 125430 points

See Chapter 9 "Interrupts" in the C6000 Programmer's Guide. It gives details on things that affect interruptibility of code. For example if your code is using multiple assignment as discussed in the document then you are required to make the code uninterruptible.

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Instruction fetch exception on C674