CCS 3.249 producing erroneous interrupt code?

[zilog]

I have placed my entire project here: http://wintermute.csbnet.se/~zilog/kod/styrkort_riktiga/ for you to have a look at. What is interesting is that during close examination of the assembler code in main.lst, I have found that the assembler code for #INT_EXT3 high void ChainHighCurrentIsr(void) in chain.c which is present in main.lst at adress 0x1F18 destroys the contents of register 0x5A8. Have a look below:

[Ttelmah]

That is what 'ScopeDebugViaAD does. The value passed, is put into the register at 05A8, and is then used in the routine itself. 5A8, is used as a scratch for this putpose, by each routine calling this sub.

Best Wishes

[Mogge]

This is inside an high pri interrupt routine.

The point is that the used register is not saved before being used here, and not saved afterwards, although it is used elswhere in the program.

Here is the relvant asembler from high pri int, snipped from th elst file on the link zilog gave:

In high pri interrupt:

[Ttelmah]

The compiler never 'saves' anything of this sort.
Don't confuse variables, and registers.
The only things that are saved, are _registers_. ie., the internal stuff in the processor itself (note that the stuff being 'saved', is all up in the Fxx area), and processor scratch values (the five bytes of the universal scratch area at the base of memory). _Variables_ (values used inside functions, _are not saved for interrupts_. However they are _protected_, by disabling interrupts around the routines themselves. So in this case, high priority interrupts will be disabled around the ScopeDebugViaAD function, to avoid both 'normal' routines, and those in the interrupt using the same area at the _same time_. However both _will_ use the same area, so if you rely on the value being in some way saved when you interrupt, it won't be.
This is why if you want to use the same routine, inside interrupts,and in the main code, you need to generate two copies, if you want them to be independant, and also avoid having the interrupts disabled...

Best Wishes

[Mogge]

OK
Thank you for the insight