Compiler/TMS320F28335: Assembly Language-Swap Register Values

Han SeungJae

Part Number: TMS320F28335

Tool/software: TI C/C++ Compiler

Hello

I want to put the return address value of the RPC register into the memory address pointed to by the general-purpose register XAR.

__asm(" MOVL XAR4, #0x00eb40");
__asm(" MOVL *XAR4, RPC"); // How do I fix this so that the RPC address is in #0x00eb40 pointed to by XAR4?
__asm(" ADD AR4, #1");

Thanks, Regards

Han

over 5 years ago

0 Lori Heustess over 5 years ago

TI__Guru* 93190 points

Han,

The RPC can only be used with a PUSH or a POP instruction. So you would push it to the stack and then move it from the stack to the address you want.

I'm curious why you are working with assembly instead of C? And why you need the RPC value?

Regards

Lori

0 Han SeungJae over 5 years ago in reply to Lori Heustess

Intellectual 980 points

Thanks for the answer, Lori

I am a student studying embedded security.
I'm writing code to check flow control integrity using an RPC address.

If I could know the address of the TMS320F28335's core register, I wouldn't have written it in assembly.

Are there any documents that disclose addresses of core registers?

Regards

Han

0 Lori Heustess over 5 years ago in reply to Han SeungJae

TI__Guru* 93190 points

The core registers are not memory mapped.

Regards, Lori

0 Han SeungJae over 5 years ago in reply to Lori Heustess

Intellectual 980 points

Lori

I have one more question.

__asm("PUSH RPC");
__asm(" MOVL XAR5, *-SP[2]");
__asm(" MOVL XAR4, #0x00eb40");
__asm("MOV *+XAR4[0], AR5"); // Here, 2 bytes of Low RPC are written to 0xeb40.
__asm("MOV *+XAR4[0], AR5H"); // How to put the remaining 6 bits of RPC?

Is it correct that ARnH does not change?
I think I have to use the ACC register to implement what I'm trying to do.

I wonder if there is any assembly language that can be written to memory.

Regards,

Han

0 Lori Heustess over 5 years ago in reply to Han SeungJae

TI__Guru* 93190 points

Han SeungJae said:
__asm("MOV *+XAR4[0], AR5H"); // How to put the remaining 6 bits of RPC?

To move more than 16-bits use MOVL. i.e. MOVL loc32, XARn

Han SeungJae said:
Is it correct that ARnH does not change?

I don't understand the question.

The C28x base set of instructions are documented in https://www.ti.com/lit/spru430

The FPU32 extension instructions are in https://www.ti.com/lit/SPRUHS1

Regards

Lori

0 Han SeungJae over 5 years ago in reply to Lori Heustess

Intellectual 980 points

It seems that ARnH cannot be changed with MOV instruction. Similar to this,

"AR0H-AR7H are accessed only as part of XAR0-XAR7 and are not individually accessible."

in TMS320C28x CPU and Instruction Set (Rev. F) Seems to be.

Thanks for the answer Lori. have a nice day.

Han

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Compiler/TMS320F28335: Assembly Language-Swap Register Values