I have made a webpage that shows the progress till now (little). It has pictures of the signals seen on the logic analyser. The first part describes the first developments, the last part is sort-of where I am now ... see www.pdp-11.nl/pdp11-34a/cpu/options/m7859/troubleshoot.html Any input is welcome! - Henk, PA8PDP. 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.