What does a logic probe on the (TTL) Serial Input of the SIO do when you send data? Are the Hardware Handshaking lines at the corrent levels? You could have a faulty Line reciever. If I were doing this, I would be proving the hardware, I don't see why the S/W would be failing? BTW, There is *never* a bonehead problem... Just the kind that we didn't think of.. regards. Doug Jackson CAUTION - The information in this message may be of a privileged or confidential nature intended only for the use of the addressee or someone authorised to receive the addressee's e-mail. If you are not the intended recipient, you are hereby notified that any dissemination, distribution or copying of this e-mail is strictly prohibited. If you have received this email in error please notify postmaster(a)citadel.com.au. Any views expressed in this message are those of the individual sender and may not necessarily reflect the views of Citadel Securix. Feel free to visit the Citadel Securix website! Click below. http://www.citadel.com.au