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setup-counter() question

 
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Core2



Joined: 27 Sep 2008
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setup-counter() question
PostPosted: Thu Nov 20, 2008 12:37 am     Reply with quote
I'm trying to port some code written for a PIC16F877 to a PIC18F4620. The statement in question is:
Code:
setup_counters(RTCC_EXT_L_TO_H, WDT_2304MS);

The parameter WDT_2304MS is specific to the '877 but NOT the'4620. What does the parameter 'WDT_2304MS' mean/do? The manual that I have (version 4 march 2007) just lists this as a parameter but doesn't explain its function. More importantly, how do I get this functionality ported to the 4620? Or do I even need to? The WDT base is 18ms for the '877; 4ms for the 4620. Both are being clocked at 20MHz.

My compiler version is PCWH 4.071

Thanks,
Duane
FvM



Joined: 27 Aug 2008
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PostPosted: Thu Nov 20, 2008 1:45 am     Reply with quote
Apart from what's written in a CCS C manual or found in the header files, it's a good idea to understand the underlying chip hardware before starting to write the code. Microchip datsheets are a valid source in this regard.

You'll find, that PIC18 family generally has the WDT period set by configuration bits (fuses) rather than a register. That's the reason, why you won't find an equivalent WDT setup function with this chip. The valid fuses tab shows the possible settings. A postscaler value of 512 would the setting next to the said 2304 ms with PIC16F.
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