eCap PWM

Target Category: Delfino, F280x, Piccolo

Target Sub-Category: Capture

Description: The eCap PWM block takes the ecapture unit and configures it as a PWM.

Additional information: Texas Instruments SPRU791A document.

Capture Unit: Specifies the unit to be configured.

Change Phase Dynamically: Changes the phase dynamically.

CTRPHS (phase): The phase register is loaded into the counter register when a synchronization pulse is received from the prior unit. The phase register can be continuously updated if desired.

Note: Some F280x and MSP430 devices have different functions for the same physical pin on the chip. This is referred to as multiplexing, or muxing, for short, and is done because pins are expensive. Because multiple functions compete for a given pin, you must choose the pin function. For flexibility, in some cases Texas Instruments provides multiple pins for a given function. For instance, the CANTXB function can be on pin 8, 12, or 16. Pin 8 is shared with ePWM5A and ADCSOCA0; pin 12 is shared with TZ1 and SPISIMOB; and pin16 is shared with SPISIMOA and TZ5. If you want ePWM5A on a pin, you cannot use pin 8 for CANTXB, but rather use pin 12 or 16.

Mux Pin: Selects the physical pin on the device a given function is on.

Period: Specifies the number of cycles (counter increments) of the board’s system clock to reach the end of its period. The carrier frequency of the PWM signal is determined as follows:

(System-Clock-Frequency)/(Timer-Frequency) = Carrier-Frequency

For example, 150 MHz/150 = 1 MHz.

Polarity: Controls the active high and active low.

Sync-Out: Each eCap PWM block is potentially linked to the next highest one. The link is via a synchronization pulse to load the counter with the contents of the CTRPHS phase register. The pulse can either be passed through the previous unit or generated when the counter equals the period (PRD).