TMS570LS1224: TMS570 NHET Usage

Hello,

All NHET pins provide the HR structure based on the HR clock, so all the pins can be used as HR input capture (PCNT or WCAP) or HR output compares (ECMP, PWCNT, or MCMP). All five HR instructions have a dedicated hr_lr bit (high resolution/low resolution; program field bit 8) allowing operation either in HR mode or in standard resolution mode. By default, the hr_lr bit value is 0 which implies HR operation mode.

You can use the following microcode to time stamp the free running timer. The WCAP captures the counter when a falling edge occurs. The WCAP data field (WCAP_DF) is updated in the loop succeeding the loop in which the edge occurred.

CNT {reg=A, max=01ffffffh}

WCAP { hr_lr=high, reg=A, event= FALL, pin=0, data=0}

However, only one instruction is allowed to operate in HR mode (bit cleared to 0) for one pin. We can set the bits in HR Share Control Register (HETHRSH) to allow two HR structures to share the same pin for input capture. If these bits are set, the HR structures N and N+1 are connected to pin N. In this structure, pin N+1 remains available for GPIO.

If we set HETHRSH[1:0] = 1, the HR structure 0 (HR0) and HR structure 1 (HR1) will share the pin HET[0]:

CNT {reg=A, max=01ffffffh}

WCAP { hr_lr=high, reg=A, event= FALL, pin=0, data=0}

WCAP { hr_lr=high, reg=A, event= RISE, pin=1, data=0} //pin=1 means using the HR1, HR0 and HR1 share pin0

The 2^nd WCAP captures the rise edge of the counter when the rising edge of input waveform at pin0 occurs.

Regards,

QJ