topic Re: inline assembly problem in Kinetis Microcontrollers

inline assembly problem

GudeADS — Tue, 25 Nov 2014 15:55:57 GMT

Hello,

I want to code a delay loop in gcc inline assembly for a K64:

	asm("push {r4}");
	asm("mov r4, delay_val");
	asm(".Lab:");
	asm("add r4, r4, #-1");
	asm("bne .Lab");
	asm("pop {r4}");

I have the push/pop instructions in here, because I have no idea how to get otherwise a free register that I can use for the small loop.

But with the push/pop instructions the exe works unstable. Any idea for a better solution?

Best Regards

Re: inline assembly problem

Jorge_Gonzalez — Tue, 25 Nov 2014 18:54:58 GMT

Hello Andreas Schmidt:

The next documents could be useful. Both are the same with some tiny differences between CW and KDS:

Extended Inline Assembly with Kinetis Design Studio

Extended inline assembly with GCC in CodeWarrior

Regards!,
Jorge Gonzalez

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Re: inline assembly problem

yasuhikokoumoto — Tue, 25 Nov 2014 22:08:07 GMT

Hi Andreas Schmidt,

according to IAR EWARM IDE, it would be described as following, given the loop variable was declared.

     asm ("mov %0,%1" : "=r" (loop),   "=r" (delay_val) : "0" (loop), "1" (delay_val));
     asm ("Lab:\n\t"
             "adds %0,%0,#-1\n\t"
             "bne Lab\n\t" : "=r" (loop) : "0" (loop) );

As for the label, it seems not to be recognized unless it will be written in one statement by IAR. By ordinary GCC even the following statements was OK.

     asm volatile ("mov %0,%1" : "=r" (loop), "=r" (delay_val) : "0" (loop), "1" (delay_val));
     asm volatile (".Lab:");
     asm volatile ("add %0,%0,#-1" : "=r" (loop) : "0" (loop));
     asm volatile ("bne .Lab");

Best regards,
Yasuhiko Koumoto.

Re: inline assembly problem

GudeADS — Wed, 26 Nov 2014 14:48:22 GMT

I will test it, when I am back at the office on Friday. Many thanks, that will help a lot!

Best Regards