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Help! Inverted PWM in 16F73

 
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azhar_multan



Joined: 24 Aug 2012
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Location: Lahore

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Help! Inverted PWM in 16F73
PostPosted: Sat Mar 08, 2014 8:53 pm     Reply with quote

Hello,
Is it possible to get inverted PWM in 16F73 ? Actually I need both inverted and non inverted outputs. So ideal solution for me is to have one module operating in normal mode and the second one in inverted mode.

Regards
Ttelmah



Joined: 11 Mar 2010
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PostPosted: Sun Mar 09, 2014 1:07 am     Reply with quote

Read the data sheet.
No.

To have inverted outputs available requires a chip with a more sophisticated module like the ECCP. Why on earth use such an old chip though?. It is not flagged as obsolete yet, but cannot be far from being so. In general newer chips offer extra features like the ECCP, and are cheaper as well.
temtronic



Joined: 01 Jul 2010
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PostPosted: Sun Mar 09, 2014 5:47 am     Reply with quote

As MR. T points old, 'ancient' PIC.....however if you're stuck using it, simply add an inverter to the PWM output pin.
Depending on the overall speed of the project, you probably will not notice any effect of the small propagation delay of the inverter.
Another option, again if a small delay is OK, is to select another I/O pin and invert it's output based upon the PWM signal.This also could work for you , though there will be a greater delay due to the program reading,deciding, setting I/O bits.
For low frequency PWM(<20KHz) or non critical loads( lights,audio) either method will work.
I do suggest that you use a new PIC though as Mr. T. says, if possible!

hth
jay
asmboy



Joined: 20 Nov 2007
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PostPosted: Sun Mar 09, 2014 4:18 pm     Reply with quote

Quote:

both inverted and non inverted outputs


but be aware that if you stick with antique parts
that the inverter approach suggested,
can make "shoot-through" trouble at higher frequencies,
especially if you are using the two signals to drive a synchronous
buck converter or similar totem-pole mosfet pair,
due to asymmetric switch time delays,
quite possible in the LOAD side of your circuit.

Not knowing the frequency or your circuit- i
can't comment further.

using a more suitable PIC is the real answer here.
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