CCS/LAUNCHXL-F28377S: Parameter of Assembler Function in C

Hi Jonas,
b0 will be at *-SP[3]. The calling function will place stack argument first, and then the return program counter (RPC) at *-SP[2] before calling asmfunc(). To verify that b0 is at *-SP[3] you can first step into the assembly function in the disassembly window, find out what SP is from the register view, and then examine the words before that address in the memory browser.

for example, if you find SP = 0x8003 as you get into the assembly function then open up the mem browser window and see if the value 8 is at 0x8000.

Hi Vishal,
Thanks for your answer. I solved the Problem for this example (b0 was placed in XAR4 register, but i have the same Problem with another.
I hope you can help me.


C-Code:

extern unsigned int asmfunc( int Vref, int Vadc, int b0, int a1, int c1, int d);

void main(void)
{
test = asmfunc( 4, 5, 8, 200, 2, 40);
}


Assmbly-Code:

.global _asmfunc

_asmfunc:
; AL = 4
; AH = 5
; XAR4 = 8
; XAR5 = 200





Where is Variable c1, d placed?

How can i add for example Vref+b0? ; Vref is placed in AL
ADD AL, ???

Like this:
ADD AL, *-SP[3] ; which number is correct and why?

Thank you so much,
Jonas

Hi,

still have this Problem. Can anybody help me?

Check out www.ti.com/.../litabsmultiplefilelist.tsp

Hopefully that helps.

Hi Jonas,

Sorry for the delay, i didn't see your response to my post earlier.

From the compiler guide (SPR514, section 7.3.1), 

(e) Remaining 16-bit arguments are placed in the order AL, AH, XAR4, XAR5 if they are available.
4. Any remaining arguments not placed in registers are pushed on the stack in reverse order. That is, the
leftmost argument that is placed on the stack is pushed on the stack last. All 32-bit arguments are
aligned to even addresses on the stack.

 

So, d1 and c1 should have been placed on the stack as shown

 

;; |_______|<- Stack Pointer (SP)
;; |_______|<- c1 (SP-1)
;; |_______|<- d1 (SP-2)
;; |_______|<- return pc of calling function (SP-4)

 

Jonas Hemmer said:

How can i add for example Vref+b0? ; Vref is placed in AL

ADD AL, @AR4 ; adding Vref (AL) and b0 (lower half of XAR4)

ADD AL, @AR4 overwrites the original Vref value so if you need Vref for other calculations you should save AL to the stack or another ARn register before the addition

Thanks for your quick respone.
The original Problem is how to adress the stack

How can i add for example Vref+c1?
like this:
ADD AL, *–SP[1] ???

This does not work in my example

Thank you very much,

Jonas

I have to thank both of you very much.
Vishal your description above this comment is right. This works.
And the workshop sheet is very helpful too.

Regard,

Jonas