Hi Chris,

Framing errors are normally caused by serial data coming in at the wrong baud rate or noise. Your pulse is causing a logic 0 to be seen where the hardware USART expects to see the stop bit.

If you add a framing error test & a solution to clear it, then you shouldn't see the continuous pulse stream.

Unless you have an ongoing problem with noise pulses or a baud rate missmatch, this should clear the problem, and you should only see the single pulse on entry into the framing error test routine.
Code:
ChrIn VAR BYTE
Junk   VAR BYTE

RXLOOP:
   HSERIN 10,NOCHR,[ChrIn]
   GOTO RXLOOP

NOCHR:

' Test for & clear framing error
IF FERR THEN              ' IF RCSTA.2 = 1
    Junk = RCREG         ' Read RCREG to clear error
    PulsOut PortC.2,10 ' Pulse to see what's happening
ENDIF
GOTO RXLOOP
You can test other conditions pretty much the same;
Code:
' Test for & clear overrun
IF OERR THEN             ' Test OERR for overrun condition
    CREN = 0                ' Disable receive
    CREN = 1                ' Re-enable & clear OERR flag
ENDIF

' Test for & clear remaining data in buffer
WHILE RCIF                ' Trash left over characters in RCREG
     Junk = RCREG          
WEND
GOTO RXLOOP