labels and the __asm()

Gigo Dret

Hello,

I'm trying to create my own analog for __delay__cycles() for am335x PRU with a variable argument not a constant as it is in original function.
I wrote the following code but the compilation gives me some error.

void delay(register uint32_t x)
{
  __asm__ __volatile__
  (
	" WAIT: \n"
	" SUB r14, r14, 1 \n"
	" QBNE WAIT, r14, 0 \n"
  );

}

and hereare errors:

ERROR! at line 1043: [E0003] Invalid instruction
WAIT:

ERROR! at EOF: [E0300] The following symbols are undefined:
WAIT

I didn't found the right way of using labels in inline asm in datasheets.

How to make it?

over 9 years ago

0 Chester Gillon over 9 years ago

Guru 92251 points

Gigo Dret said:
I didn't found the right way of using labels in inline asm in datasheets.

A label must start on column 1 of a line, since leading white-space causes a token to be treated as an instruction. i.e. try:

void delay(register uint32_t x)
{
  __asm__ __volatile__
  (
    "WAIT: \n"
    " SUB r14, r14, 1 \n"
    " QBNE WAIT, r14, 0 \n"
  );

}

See section 4.5 Source Statement Format of PRU Assembly Language Tools v2.1 User's Guide SPRUHV6A for more details.

0 Gigo Dret over 9 years ago in reply to Chester Gillon

Prodigy 120 points

thank you,

that works! syntax ckeck passed.

0 George Mock over 9 years ago in reply to Gigo Dret

TI__Guru**** 249380 points

Consider using the compiler intrinsic __delay_cycles instead. Search for it in the PRU compiler manual.

Thanks and regards,

-George

0 Gigo Dret over 9 years ago in reply to George Mock

Prodigy 120 points

Hello George,

unfortunately __delay_cycles() takes only constant parameter but I need it to be varyable.

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labels and the __asm()