How to verify HS_PLL clock speed

[Darrel Taylor]

Just wanted to add that the PLL only starts up properly on Power-Up.

The first time you program a chip with the PLL turned on, it won't actually start working at x4 untill you turn the power off and on again. A simple reset of MCLR wont do it.

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[Bruce]

And it "does" work with a 4MHz TTL clock input with HSPLL set. Just tested it. __CONFIG _CONFIG1H,_OSCS_OFF_1H & _HSPLL_OSC_1H

You just can't use the OSC2 pin for I/O or clock/4 output without using EC or ECIO mode.

[CocaColaKid]

On that note then, using this code it should run at 16MHz internally, correct?

@ __CONFIG _CONFIG1H, _OSCS_OFF_1H & _HSPLL_OSC_1H
@ __CONFIG _CONFIG2L, _BOR_ON_2L & _PWRT_ON_2L & _BORV_45_2L
@ __CONFIG _CONFIG2H, _WDT_ON_2H 
@ __CONFIG _CONFIG4L, _STVR_ON_4L & _LVP_OFF_4L & _DEBUG_OFF_4L

Main:
HIGH portd.1
PAUSE 500
LOW portd.1
PAUSE 500
GOTO Main

This reminds me of the old 486DX2 and DX4 microprocessors

[Bruce]

I'm using MPASM version 4.02 which complains if I use the old __config options, so I replaced the old options in the .inc file with:
CONFIG OSC=HSPLL,OSCS=OFF,LVP=OFF,PWRT=ON,BOR=ON,WDT=OFF, BORV=25,WDTPS=128,CCP2MUX=OFF,STVR=OFF

DEFINE OSC 16

LOOP:
HIGH 0
PAUSE 500
LOW 0
PAUSE 500
GOTO LOOP

With the 4MHz TTL input to OSC1, it produces .5 S pulses on RB0. So assuming your programmer isn't altering config fuse settings, and you're getting it programmed with HSPLL, then it should definitely be running at 16MHz internally.

[CocaColaKid]

I added the DEFINE OSC 16 and it only flashes about once every 2 seconds. I have cycled power and still the same thing.

[Bruce]

If you're programming in-circuit, did you cycle power?

As Darrel mentioned previously, you need to cycle power OFF then back ON when switching to HSPLL mode.

With DEFINE OSC 16 -- a 2 second pause is what you'll see if the PLL isn't locked in. It's running directly from the 4MHz TTL clock input until the PLL circuit locks-in, and kicks in the 4x PLL.

[CocaColaKid]

I think I just found my problem. The bootloader doesn't seem to be changing the configuration bits properly. I programmed the PIC in the EPIC programmer and it works fine now. Thanks for the help. I'll look further into the other programming method tomorrow.