Help my PWM

Started by soso soso April 3, 2006

Question about PWM output:

I am using BX24s PWM (pin26) to control a 24V DC motor with a driver LMD18200, and it has no problem at all. However, suddenly, the PWM doesnt work, while other function is fine. Also I have checked by using the dual PWM problem provided, the following cases can be observed.

Firstly, I have 2 BX24 (may called BX24-a and BX24-b) and those both pin26, 27 dont work now.

For BX24-a
Pin26 always output a constant voltage about 3.5V. Even I program it to be low, PutPin (26 , 0), It also output 3.5V.

Pin27 is able to output PWM but with low frequency (rate-setting is 5, and use 8-bit mode). If higher frequency, 14 kHz, is set, the waveform look like a capacitors charging and discharging curve, and wont reach 0V.

For BX24-b
Pin26 can output PWM with low frequency, but it wont reach 0V such that the single is triggered between 5V and 3.5V. For high frequency, the waveform look like a capacitors charging and discharging curve.

Pin27 is the same as Pin26 (BX24-b).

Is my BX24 broken? or any other reason. I have tried to program Timer2 to output PWM, it works well. But now I dare not to use Time2 in my project before the above question solved. Please tell me the answer.


YM - uT

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