SimonZhu

maybe an issue in the datasheet of MC68HC908AZ32A

Discussion created by SimonZhu on Nov 30, 2006
Latest reply on Nov 30, 2006 by bigmac

I don't quite understand some statements in the datasheet of MC68HC908AZ32A. In the page 288 of "MC68HC908AZ32A.pdf Rev 0.0" file there are some statement as below:

"The value in the TIMA counter modulo registers and the selected prescaler output determines the frequency of the PWM output. The frequency of an 8-bit PWM signal is variable in 256 increments. Writing $00FF (255) to the TIMA counter modulo registers produces a PWM period of 256 times the internal bus clock period if the prescaler select value is $000".
"The value in the TIMA channel registers determines the pulse width of the PWM output. The pulse width of an 8-bit PWM signal is variable in 256 increments. Writing $0080 (128) to the TIMA channel registers produces a duty cycle of 128/256 or 50%."
 
I understand the the first section, but I think maybe there is an issue in the second section. Writing $0080 (128) to the TIMA channel registers should produce a duty cycle of 129/256, but not 128/256. If the statement is correct, then which duty cycle will be produced if we writing $0000 to the TIMA channel registers? My test result is 1/256 duty cycle is produced.
 
Thanks,
Simon

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