1. For the 16F628 you would need CMCON = 7 to setup RA as digital. It doesn't hurt to use this with the F877A part either. Even though the F877A POR default is CM2:CM0 = 111 it never hurts to make 100% sure.

2. You're using the wrong baud mode for SERIN. 396 would be used for SERIN2 @ 2400 bps, driven, true.

For SERIN you would use mode 0 or --

Serin porta.0, 0, B0 ' B0 = input character

Or, since you're already using Include "modedefs.bas" --

Serin porta.0, T2400, B0 ' B0 = input character