Debugging at 64MHz

Will Reeve · Joined: 30 Oct 2003 Posts: 209 Location: Norfolk, England

Hi,
Using a 18F26K20 with the internal OSC at 64MHz. I am a little confused as to the correct use of the fuses and setup_oscillator() function, the help seems to suggest that the setup_oscillator isn't necessary with the correct fuses. The only way I can get the PIC to run at 64MHz is a single fuse of
#FUSES INTRC_IO
and a setup_oscillator(OSC_64MHZ).

However when debugging the speed is reported as "Ready MCU at 1.00MHz".

I have delay (clock=64000000) and a 1second pulse is measured correctly on my 'scope.

I would have thought a INTRC_IO and a H4 would do the same job in fuses but it appears not.

Compier version is 4.099.

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

When you use the internal oscillator in PLL mode, the PLL has to be
enabled in software. This is done with the setup_oscillator() statement.
You can see this by looking at the parameters for setup_oscillator()
in the 18F26K20.h file. The OSC_64MHZ value includes the OSC_PLL_ON
bits in it.

However, there is an alternate way. You can specify "internal" in the
#use delay() statement. Then you don't need to call setup_oscillator().
CCS will put the instructions to setup the oscillator in the start-up code.