Hello to all forum members, hopefully somebody can point me in the right direction.

I have setup a simple PIC18F4520 demo board, using a 10Mhz crystal. My Rx + Tx pins are connected directly to a Maxim 3080 rs485 transciever. PIC port D0 is connected to my { driver enable, (!reciever enable) } on the transciever. I am using a very short run of rj45 cable with no biasing or terminating resistors. I am using a baud rate of 115200.

A PC is acting as bus master and sending simple ascii strings to the PIC using realterm.

Sending characters from the PIC to the PC works fine, no characters are lost.

Only the first 3 characters are triggering the rx interrupt when transmitting from the PC to the PIC.

For example, I have set a breakpoint on the interrupt handler. When I send 'abcde' from the PC terminal, the breakpoint is only triggered for the 3 chars, a, b and c. The additional chars seem to be ignored.

I could work around this, however I would like to understand what is happening.

Thanks !

David