[GPS_Standard] PIC18F2220 versus PIC18F2221

[Martein Bakker]

Hi list!

I have succesfully built the VE2ZAZ GPS standard. 

Initially I used PIC18F2221 as I could not get PIC18F2220. The 18F2221 is supposed to be the newer and better part and successor of 18F2220. I went through the datasheets and could not see any difference that would prevent the 18F2221 to work in this application. However it failed to work partially in practice. Montrol software could talk with it, but the measured frequency was always 0 and strange enough the frequency difference was not 0, but the MSB byte was always 0! Obviously it did not lock.

Does anyone know why the 18F2221 does not work with this application? It would be great if the firmware is compatible with this device as it is much cheaper.

Best regards
Martein 
pa3ake