Architecture and Instruction Set of the C6x Processor - Digital Signal Processing and Applications with the C6713 and C6416 DSK - page 108

// Code_casm.c Calls ASM function.If code match slider values

#include <stdio.h>
short digit1=1,digit2=1,digit3=1,digit4=1;//init slider values

main()
{
short code1=1,code2=2,code3=2,code4=4; //initialize code
short result;

DSK6713_init(); //init BSL

DSK6713_DIP_init(); //init dip switches

while(DSK6713_DIP_get(3) == 1) //continue til SW #3 pressed

{
if(DSK6713_DIP_get(0) == 0) //if DIP SW #0 is pressed
{ //call ASM function
result=codefunc(digit1,digit2,digit3,digit4,code1,code2,code3,code4);
if(result==0) printf("correct match\n");//result from ASM function
else printf("no match\n"); //correct match or no match

}
}
}

FIGURE 3.15. C program that calls an ASM function to detect a four-digit code
( code_casm.c ).

; Code_casmfunc.asm ASM function->if code matches slider values

.def _codefunc ;ASM function called from C
_codefunc: MV A8, A2 ;correct code

MV B8, B2

MV A10, A7

MV B10, B7

CMPEQ A2,A4,A1 ;compare 1st digit(A1=1 if A2=A4)

CMPEQ A1,0,A1 ;otherwise A1=0

[A1] B DONE ;done if A1=0 since no match

NOP 5

MV B2,A2

CMPEQ A2,B4,A1 ;compare 2nd digit

CMPEQ A1,0,A1
[A1] B DONE
NOP 5

MV A7,A2

CMPEQ A2,A6,A1 ;compare 3rd digit

CMPEQ A1,0,A1
[A1] B DONE
NOP 5
MV B7,A2

CMPEQ A2,B6,A1 ;compare 4th digit

CMPEQ A1,0,A1

DONE: MV A1,A4 ;return 1 if complete match

B B3 ;return to C program

NOP 5
.end
FIGURE 3.16. ASM function called from C to detect a four-digit code
( code_casmfunc.asm ).