TMS570LS3137: HALCoGen startup code initializing SPSR in System Mode

_MM_

Expert 1995 points

Part Number: TMS570LS3137
Other Parts Discussed in Thread: HALCOGEN

Hello,

I did not find an answer to the original doubt: according with the reference material, actually even if system mode is a privileged mode, it has no SPSR. It makes sense for me since in system mode there are no exceptions and then no reason to have dedicated SPSR.

So, why in the portion of sys_core.asm, at the following portion:

; Switch to System Mode ( Shares User Mode registers ) (M = 11111)
        cps #31
        mov lr, r0 
        mrs r1,cpsr
        msr spsr_cxsf, r1

the last line should not be removed ?

over 7 years ago

0 Sunil Oak over 7 years ago

TI__Mastermind 49120 points

Hi Marco,

Thanks for the catch! Yes, the last two lines of the code you posted are not necessary since there is no SPSR for the System and User modes.

I will add an internal ticket to update the template sys_core.asm file for a future release of HALCoGen.

Regards,
Sunil

0 _MM_ over 7 years ago in reply to Sunil Oak

Expert 1995 points

Thanks Sunil. Can you confirm me also that both the last two lines can be removed? Then, it would stop to moving R0 to the LR.

0 Sunil Oak over 7 years ago in reply to _MM_

TI__Mastermind 49120 points

Marco,

mrs r1,cpsr
msr spsr_cxsf, r1

The above two lines can be removed when the CPU mode is System mode. So only the link register in system/user mode is initialized.

Regards,
Sunil

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TMS570LS3137: HALCoGen startup code initializing SPSR in System Mode