bon@JPL-VLSI.ARPA (02/04/86)
This is a request for information on the availability of a clock which can be read from 2 microVAXes for a real-time application. We are implementing a robotic task which will have one microVAX II doing vision and another commanding robot arms using visual feedback. My problem is conceptually very simple -- I need a precise time base which is consistent for both machines to about 0.1 millisecond. Ideally, I would like to have a single millisecond time-of-day clock which takes care of its own register incrementing, etc., but which can be read simply by doing a load from memory to memory-mapped I/O locations. I don't care about interrupts or anything more sophisticated. Another possibility would be to have a clock in each VAX and start them based on an externally-generated pulse. The consistency achieved by this method depends on both the delays between receipt of the pulse and activating the clocks, and on the accuracy of crystals in each clock to maintain synchronization -- I'm not crazy about having to rely on these. If anyone knows of vendors which sell devices which might help us with our time-keeping problem, I would appreciate hearing from you with their names and addresses/phone numbers. Also, if anyone has solved similar problems, I would be interested in hearing how. Thanks in advance for any help you can give. Bruce Bon Bon@JPL-VLSI.ARPA