Forum Post: Question about register usage in C called assembly code for C6000

Hi,

I write an assembly code function which is called by a C program for C6000 DSP. Although I have read the C call convention on spru187t.pdf, it is still not clear to me. For simplicity, I have two input parameters and one output parameter in function calling. This will use A4, B4 for input while A4 for output. What registers should I save in assembly code?

I notice that A0 to A9 are reserved by parent function while others reserved for child. I do not know what action in the assembly code to deal differently with those two group registers. Could you explain it to me?

Thanks,