DEC OMNIBUS Signal Definitions

Hi, everyone, I'm looking for a reference document that defines the functions of the various signals on the DEC PDP 8/e/f/m Omnibus. In Volume 1 of the Maintenance Manual, there is an Omnibus locator that gives the names of the various signals and which pin on the backplane each function exists on, but there's nothing that I can find that gives the function definition of each of the signals. The information is buried in the test of the processor description, but there doesn't seem to be a place that I can find that summarizes the information all in one place. I'm troubleshooting a DEC RK8E disk controller that causes problems on the Omnibus when the controller boardset is installed in an otherwise fully operational PDP 8/e, and knowing what the various bus signals do would make the task a whole lot easier. Does anyone know of a document like this? Rick Bensene