RTOS/AM5728: DSP delay function

Hi,

In the Linux, the udelay() is a delay in 1us precision. On the C66x DSP side, you can use TCSL and TCSH counter. They are CPU cycle counter, TSCL is the lower 32 bit portion and TSCH is the higher 32 bit portion. In your system, you have the PLL setting for the DSP clock (through GEL, or secondary bootloader). It is most likely DSP runs at 750MHz (you need to double check), that is 1 cycle is 1/0.75 = 1.33 ns. If you delay 750 cycles, that is 1 us delay. 1500 cycles is 2us delay ...

For the code implementation, you can see below:

extern volatile unsigned int cregister TSCL;
TSCL = 1; //enable it, only need to do once

static uint32_t readTime32(void)
{
uint32_t timeVal;

#if defined (_TMS320C6X)
timeVal = TSCL;
#elif __ARM_ARCH_7A__
__asm__ __volatile__ ("MRC p15, 0, %0, c9, c13, 0\t\n": "=r"(timeVal));
#else
/* M4 specific implementation*/
static uint32_t simuTimer = 0;
simuTimer++;
timeVal = simuTimer;
#endif
return timeVal;
}

void cycleDelay (uint32_t count)
{
uint32_t start = (uint32_t)readTime32();

while (((uint32_t)readTime32() - start) < count);
}

If you want to introduce several seconds delay a time, you need to use TSCL and TSCH together. Otherwise, 32-bit TSCL is enough for your purpose.

Regards, Eric