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Pulse width Modulator behavior in low and high speed mode

Question asked by Jose Alfaro on May 9, 2013
Latest reply on May 24, 2013 by Pascal Irrle

I am using CW 10.3 with a MC9S08LL64 chip.  I am setting this chip to run in two modes (high 4.2MHz and low 1.05MHz). 

By setting this two modes, I am using a PWM on TPM2CH0 and set it to be 100 Hz period with pulse width of 0, 100 and 200 uSecs.  Generating an interrupt every 10 mSeconds to control the pulse output.

Using Processor expert, creates a HighComp table with 3 values (0x00, 0x01A3 and 0x0347) and a LowComp table with 3 other values (0x00, 0x69 and 0xD2). 

I am finding that while in Low mode and setting the pulse width to 0 uSecs, the pulse is actually having a 100 - 125 uSec width for a long period of time (20 mSec variable).

Everything works correct while in high speed mode.

 

Any ideas

 

Jose Alfaro

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