Datasheet

Mode” on page 1116). On the next counter cycle in periodic mode, the counter reloads its start value
from the GPTMTnILR and GPTMTnPR registers and continues counting until disabled by software
clearing the TnEN bit in the GPTMCTL register. The timer is capable of generating interrupts based
on three types of events: rising edge, falling edge, or both. The event is configured by the TnEVENT
field of the GPTMCTL register, and the interrupt is enabled by setting the TnPWMIE bit in the
GPTMTnMR register. When the event occurs, the CnERIS bit is set in the GPTM Raw Interrupt
Status (GPTMRIS) register, and holds it until it is cleared by writing the GPTM Interrupt Clear
(GPTMICR) register . If the capture mode event interrupt is enabled in the GPTM Interrupt Mask
(GPTMIMR) register , the GPTM also sets the CnEMIS bit in the GPTM Masked Interrupt Status
(GPTMMIS) register. Note that the interrupt status bits are not updated unless the TnPWMIE bit is
set.
In addition, when the TnPWMIE bit is set and a capture event occurs, the Timer automatically
generates triggers to the ADC and DMA if the trigger capability is enabled by setting the TnOTE bit
in the GPTMCTL register and the CnEDMAEN bit in the GPTMDMAEV register, respectively.
In this mode, the GPTMTnR and GPTMTnV registers always have the same value.
The output PWM signal asserts when the counter is at the value of the GPTMTnILR and GPTMTnPR
registers (its start state), and is deasserted when the counter value equals the value in the
GPTMTnMATCHR and GPTMTnPMR registers. Software has the capability of inverting the output
PWM signal by setting the TnPWML bit in the GPTMCTL register.
Note: If PWM output inversion is enabled, edge detection interrupt behavior is reversed. Thus, if
a positive-edge interrupt trigger has been set and the PWM inversion generates a positive
edge, no event-trigger interrupt asserts. Instead, the interrupt is generated on the negative
edge of the PWM signal.
Figure 16-4 on page 1115 shows how to generate an output PWM with a 1-ms period and a 66% duty
cycle assuming a 50-MHz input clock and TnPWML =0 (duty cycle would be 33% for the TnPWML
=1 configuration). For this example, the start value is GPTMTnILR=0xC350 and the match value is
GPTMTnMATCHR=0x411A.
December 13, 20131114
Texas Instruments-Advance Information
General-Purpose Timers