TMS570LS3137: HALCoGen startup code initializing SPSR in System Mode

Charles Johnston

Part Number: TMS570LS3137

Hello,

The file sys_core.asm, function _coreInitRegisters_ contains the following:

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

But there is no SPSR banked register for System mode.

Can the last three lined be removed, or is there a reason for this code?

Thanks, Charlie Johnston

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

over 8 years ago

0 Chuck Davenport over 8 years ago

TI__Guru 59540 points

Hi Charlie,

I don't have access to all of the documentation at the moment to fully answer your question. I will have another look at it tomorrow morning and get back with you.

0 Chuck Davenport over 8 years ago

TI__Guru 59540 points

Hello Charlie,

The SPSR is the Saved Program Status Register and is accessible in privileged modes and yes, the Cortex R4 TRM does specify that it is not a banked register which is why it takes the special instructions to access it using MRS and MSR instructions.

This register is used during the sys_core.asm when all of the various modes are walked through to initialize all of the various stacks. These lines cannot be commented as they are key to configuring the cores for operation.

Please reference section 2.6 of the ARM Cortex-R4 TRM for more information.

0 Charles Johnston over 8 years ago in reply to Chuck Davenport

Expert 2690 points

Hi Chuck,

I'm looking at DDI0363G as the ARM Cortex-R4 TRM which doesn't have a section 2.6. Which document number are you referring to?

Thanks, Charlie Johnston

0 Chuck Davenport over 8 years ago in reply to Charles Johnston

TI__Guru 59540 points

Hi Charlie,

I am referencing the same document that our safety manual links to for the Cortex R4 and R4F Terchnical Reference Manual (r1p3) in the ARM infocenter. Here is the link provided in our Safety Manual infocenter.arm.com/.../index.jsp. To be more exact, the information is in section 2.6.1.

0 Charles Johnston over 8 years ago in reply to Chuck Davenport

Expert 2690 points

Thank you, Chuck.

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TMS570LS3137: HALCoGen startup code initializing SPSR in System Mode