I wrote a C program to take a hex ascii input from the keyboard
that creats an RS232 stimulus file for use with the MPLAB.  Does
that sound like what you need?

>Date:  Mon, 2 Feb 1998
>From:  Mike Montgomery <mike@ANALI.DEMON.CO.UK>
>Subject: Stimalus files
>
>Hi
>       Does anyone have a util that will convert TEXT/BIN/HEX file
>   to a stimulus file to reproduce RS232 input.
>
>thanks