I vaguely remember the AY-1315 (not sure!!), but that 40-pin IC was a 8-bit data parallel to serial data bi-directional converter. A sort of a UART. To send serial data, you put the 8-bit data parallel in its 8 input pins, strobed an other pin and then the data with start- and stopbit came out of another pin :-) But, as said, memory is vague, but it might help ... - Henk. This message and attachment(s) are intended solely for the use of the addressee and may contain information that is privileged, confidential or otherwise exempt from disclosure under applicable law. If you are not the intended recipient or agent thereof responsible for delivering this message to the intended recipient, you are hereby notified that any dissemination, distribution, or copying of this communication is strictly prohibited. If you have received this communication in error, please notify the sender immediately by telephone and with a "reply" message. Thank you for your cooperation.