MIBAM and 40Mhz (10Mhz x 4 PLL) 18F452 - Chip does not work

Hi there,

I am using DT's MIBAM routine with 20 port/LEDs.
With 18F452, set to 4x10Mhz PLL clock, chip does not work.

It works with 20Mhz HSOSC with no problem.

Any ideas why it does not work with 40MHz?
I will use 24 ports with 40MHz.

Thank you.

Hi Sayzer,

Does it do anything at all? Or is it just dead at that point?

The circuit has a digit to show the animation mode number. At 40MHz, sometimes( ! ) the digit comes and goes. But port pins used for MIBAM never works.

Thank you Darrel.

Can you confirm that the PIC does indeed work at 40MHz? Maybe you are having a hardware problem with the oscillator (I had something similar once using a breadboard).

Can you add a simple test, maybe blink an LED at a fixed interval?

Sayzer,

After checking the program, going through the math, compiling for an 18F @ 40mhz and not finding anything wrong ... I put together a breadboard with an 18F4620 running at 40Mhz with a 10Mhz crystal and 24 LED's.

It works fine.

BAM_INFO says ...
Message[301]: MESSAGE: ('BAM_INFO' - MinPeriod= 173 inst, Cycle= 22774 inst, Pins= 24, FREQ= 219 Hz)

Thank you very much Darrel.

I also went through the hardware, and found nothing wrong.
10Mhz xtall, 15pf caps, HSPLL (DEF. OSC 40) does not work.
20Mhz xtall, 15pf caps, HS_OSC (DEF. OSC 20) works.

Testing it with 40Mhz using a test code (without MIBAM) is ok.

Quote:

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Originally Posted by Darrel Taylor

...
I put together a breadboard with an 18F4620 running at 40Mhz with a 10Mhz crystal and 24 LED's.

It works fine.
...

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Sayzer was using an 18F452, not an 18F4620, maybe it's a problem with a particular chipset and not the 18F family?

One thought, Sayzer, did you try with another 18F452? That would rule out a defective unit.

And if you want to rule out the breadboard, try it on another one. I've had only one breadboard so far with a defective track in it.

And a really dumb question, did you confirm that power to the circuit was good? Forgetting to readjust the voltage or current on a variable power supply like the one I use could make for freaky results; not saying that I ever did that noob mistake. :D