External Oscillator with PIC MCU

winson · Joined: 03 Dec 2008 Posts: 24

Hi,

I am using PIC microcontroller. If I wish to use an external crystal oscillator for my project, then is it necessary to include some lines of code in my program to tell that I'm using an external oscillator now? If it is needed, then how to write this in CCS C language?

Thanks a lot.

ckielstra · Joined: 18 Mar 2004 Posts: 3680 Location: The Netherlands

For the different oscillator configurations you have to specify a Configuration bit. CCS calls these settings 'fuses'

winson · Joined: 03 Dec 2008 Posts: 24

SherpaDoug · Joined: 07 Sep 2003 Posts: 1640 Location: Cape Cod Mass USA

NOLVP = No Low Voltage Programming
NOWDT = No Watch Dog Timer

LVP allows the PIC to generate its own high voltage for programming instead of taking it from the MCLR pin. This can cause accidental programming under certain circumstances, which trashes your programmed code.
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winson · Joined: 03 Dec 2008 Posts: 24

Thanks SherpaDoug.

So every time just put

#fuses HS,NOWDT,NOLVP

Then can throw all the headache away.

SherpaDoug · Joined: 07 Sep 2003 Posts: 1640 Location: Cape Cod Mass USA

Well it depends on what you are doing. If your clock is a crystal slower than 4 MHz you don't want HS (see ckielstra's post), and if your product is running in the real world you may want the Watch Dog enabled.... All those choices are useful for somebody.
_________________
The search for better is endless. Instead simply find very good and get the job done.