Quote Originally Posted by peter_wiersig View Post
We have
1 PIC18F2550
1 PIC18F2423

Config 2550
Code:
@        __CONFIG    _CONFIG1L, _PLLDIV_5_1L & _CPUDIV_OSC1_PLL2_1L & _USBDIV_2_1L
@        __CONFIG    _CONFIG1H, _FOSC_HSPLL_HS_1H & _FCMEN_OFF_1H & _IESO_OFF_1H
...
DEFINE OSC 20
We measured the 2550 + 2423 TX lines with an oscilloscope until we found a HSER_BAUD rate that matched and we got no problem communicating between those two PICs.

Does it make any sense that those two HSER_BAUD settings differ?
Those fuses let the 2550 run at 48 MHz, we coded a sample program and measured again with our oscilloscope

Code:
DebugLoop:
TOGGLE PORTC.1
PAUSE 100
GOTO DebugLoop
Which showed a ~40 ms pulse on the 2550 and a 100 ms pulse on the 2423, from there it was back to the data sheets and we found our error.

config 2550
Code:
@        __CONFIG    _CONFIG1L, _PLLDIV_5_1L & _CPUDIV_OSC1_PLL2_1L & _USBDIV_2_1L
@        __CONFIG    _CONFIG1H, _FOSC_HS_1H & _FCMEN_OFF_1H & _IESO_OFF_1H
DEFINE OSC 20