[Icc-mot] uexec and XGATE chip

[Peter Lissenburg]

Hi Edward,
	thanks for that, important point I had missed, although I should have 
questioned the extra stuff NoIce was showing me.
Before the
CLR 1,-SP
should I not make another entry to modify? by
psha
?

I'll have a go and learn more....
Thanks.
Peter L.



Edward Karpicz wrote:
> Peter Lissenburg wrote:
> 
>> Hi Richard and all,
>> I'm starting to use the uexec code on an xgate chip. Finding a 
>> problem(s),
>> that I have not tracked down yet, so I thought I'd ask if anyone has done
>> this and solved this (unknown as yet!) problem.
>> Thanks for any insights.
>> Peter L.
>>
>>
> 
> Hi Peter,
> 
> S12X CCR is 16bits wide, while S12 CCR is 8bits wide. As a result 
> interrupt stack frames do differ. This doesn't hurt anybody except when 
> code has to manipulate interrupt stack frame. I found two "suspect 
> places" in hc12.s file from examples12\uexec_dp256.zip, please search 
> for "create an interrupt stack frame":
> 
> ...
> _UEXC_SavregsAndResched::
> ; first create an interrupt stack frame
> pshy
> pshx
> pshd  ; what a concept, not A:B
> tpa
> anda #0xEF ; re-enable interrupt when it "returns" since
> psha  ; Defer() disables interrupt
> ...
> 
> In bottom three lines 8bit CCR is pushed to the stack. CCRh should be 
> pushed next. CCRh holds interrupt priority level and it should be zero 
> for foreground tasks. So add CLR 1,-SP after psha and it should get 
> ported, I think.
> 
> ...
> _UEXC_SavregsAndResched::
> ; first create an interrupt stack frame
> pshy
> pshx
> pshd  ; what a concept, not A:B
> tpa
> anda #0xEF ; re-enable interrupt when it "returns" since
> psha  ; Defer() disables interrupt
>   CLR   1,-SP
> ...
> 
> ...
> _UEXC_StartNewTask::
> lds _uexc_current_sp
> ; make KillSelf as the "return pc" of a new task, so if it
> ; ever returns, it will reclaim the storage
> ldd #_UEXC_KillSelf
> pshb
> psha
> ldd _uexc_current_func
> pshb
> psha
> ; create an interrupt stack frame
> pshy
> pshx
> pshd
> tpa
> anda #0xEF ; re-enable interrupt
> psha  ;
>   CLR   1,-SP
> ...
> 
> 
> Regards
> Edward
> 
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