I would like to have a very slow PWM (1Hz - 2Hz) on the Teensy 4.0 and from my reading of the i.MX RT1060 Processor Reference Manual, I believe that I will need to source the PWM with an EXT_CLK, because the IPBus Clock is too fast. Is IPBus = 100MHz? However, I can't figure out how to connect to the EXT_CLK. In the section on EXT_CLK, the manual says "This signal allows a source external to the PWM (typically a timer or an off-chip source) to control the PWM clocking." But it doesn't say how to source that signal. If I could connect it to the output of a timer, that would give me a lot of flexibility on clocking. How do I select the source for the PWM EXT_CLK??