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CCS, CCP, PIC18, and multiple native PWM outputs

 
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CCS, CCP, PIC18, and multiple native PWM outputs
PostPosted: Wed Jan 05, 2005 9:21 pm     Reply with quote

Hello,

I was looking through the CCS documentation, and the documentation for the PIC18F458, which has one CCP and one ECCP module. I am aware that for a single conventional CCP module, only one PWM output is possible. For an ECCP, the datasheet suggests to me that only one INDEPENDENT PWM is possible (P1A, the remainder being variations of this, in the form of the various bridge modes) and there appears to be only one register for adjusting the duty cycle.

However, CCS allows for the setup of a CCP1 through CCP5 (setup_ccpX) for the ECCP-enabled devices, and allows for PWM1-5 (set_pwmX_duty). If I made use of these, could PWM with varying duty cycles be output simultaneously on ports P1A-P1D? Does the compiler just bit-bang this? (i.e. will the PIC be bogged down or drop the PWM during a long ISR?)

Thanks to anybody out there who can help me with this!
PCM programmer



Joined: 06 Sep 2003
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PostPosted: Fri Jan 07, 2005 12:35 pm     Reply with quote

I didn't check the code, but I would suspect that these routines
are intended for a PIC such as the 18F4431, which has four
independent PWM modules. The 18F458 only has two PWM modules.
Look at the block diagrams in the data sheets to see this.
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