NXP Semiconductors Kinetis KE1xZ256, Reference Manual

Page: 1050 / 1325

The step 1 and 2 can be sequential or not, but they must be completed before step 3 to
ensure all settings are ready before pulse width measurement is enabled.
41.9 Usage Guide
PWT provides an accurate signal frequency measurement for both the positive and
negative portions of a periodic signal, useful for applications such as motor control. In
conjunction with a Pulse Width Modulated signal it can effectively be used to implement
a highly accurate closed loop motor control system, or any other system in which it might
be necessary to measure a periodic signal frequency and duty cycle, providing not only
accuracy but also high flexibility.
41.9.1 Edge detection, capture control and period measurement
PWT typical usage is external signal input capture and time period measurement.
Example: PWT input channel 1 capture external signal and measure its time period
• Enable the PWT module clock;
• Reset the timer channels and registers;
• Configure not to load the first counter values to corresponding registers, enable the
PWT interrupt;
• Select bus clock as clock source and enable PWT_IN1 as input source;
• Set the module enable bit to start PWT;
• Wait for the pulse width valid flag (PWTRDY) in interrupt routinue, then get the
positive and negative value(PPW, NPW) to calculate the period.
The following pseudo-code matches the described setup above:
CLOCK_EnableClock(PWT);
PWT_CS|= PWT_CS_PWTSR_MASK;
PWT_CS|= PWT_CS_FCTLE(0)|PWT_CS_PWTIE_MASK|PWT_CS_PRDYIE_MASK;
Usage Guide
Kinetis KE1xZ256 Sub-Family Reference Manual, Rev. 3, 07/2018
1050 NXP Semiconductors