PIC18F2550 USB and clock configuration

[tatokash]

One more time... with feeling.

Why does this not work with a 12MHz crystal:

[Douglas Kennedy]

Here is what I know
At 20Mhz
#fuses HSPLL,NOWDT,NOPROTECT,NOLVP,NODEBUG,USBDIV,PLL5,CPUDIV1,VREGEN,NOBROWNOUT,MCLR
The 20 mhz external crystal is pre scalled by div 5 (PLL5) to 4mhz
PLL multiplies by 16 to 96Mhz USBDIV post scales with div by 2 to 48MHZ
CPU clock is post scaled with
CPUDIV1 by with div by 2 for 48 MHZ
#use delay(clock=48000000)

At 12Mhz
#fuses HSPLL,NOWDT,NOPROTECT,NOLVP,NODEBUG,USBDIV,PLL3,CPUDIV1,VREGEN,NOBROWNOUT,MCLR
The 12 mhz external crystal is pre scalled by div 3 (PLL3) to 4mhz
PLL multiplies by 16 to 96Mhz USBDIV post scales with div by 2 to 48MHZ
CPU clock is post scaled with
CPUDIV1 by with div by 2 for 48 MHZ
#use delay(clock=48000000)
The exact same result so both should work. I have had issues with certain chips running the CPU stage at 48Mhz...I know 32Mhz ( CPUDIV2) works every time. Try 32Mhz and see if that works

[PCM programmer]

I tested this on a PicDem2-Plus with a 12 MHz crystal, with PCH vs. 4.053
and it puts out a 1 KHz squarewave on Pin B0.