So, from reading the manual for the CA plug-in it looks like the multi-trace sync signals (on pins 8 and 16) are what drive which channel is displayed when on a 500-series scope. Unlike the 7000-series, where the backplane actively selects one channel or the other, the 500-series plug-ins use the multi-trace sync signal, which appears to be a pulse that indicates the end (or start?) of a sweep. The plug-in simply multiplexes its channels over the signal pins (1 and 3) in whatever way it wants, but it can do this because it knows when a sweep starts. This means that I could conceivably have multiple plug-ins active simultaneously by switching the multi-trace sync signal to different plug-ins in a round-robin fashion.
Alternately I could set up a multi-channel chopper to merge the outputs from all three plug-ins. I wonder how fast I could chop between signals and still have it work on the 533A.
This is actually looking like something that wouldn't be too hard to do.
-- Jeff Dutky
