Hang me if I'm wrong (I've never done low-level PC programming) but aren't interrupts easier to control in DOS than in Windoze? I figure that the handshaking is imperative and needs to be precise, so maybe the inerrupts while in windows effects that. Just a thought... Tim H. In a message dated 7/15/99 1:14:10 PM Pacific Daylight Time, haroldhallikainen@JUNO.COM writes: > I'm running MPLAB 4.12 and ProMate 5.00.00 . I believe > handshaking (RTS-CTS) is working since the downloads are fine under DOS, > though it could be that Windoze is dozing while running under DOS (a DOS > session in Windoze) is faster. I'll see if I can find my RS232 breakout > box and see if the appropriate lights are flashing... >