[cctalk] Rainbow Z80 firmware

Hello everyone, I am working on a Rainbow 100A which is showing a diagnostic code on the lights at the back of 0110101. This is supposed to be Message 1 "Main Board Video". I have disassembled the 8088 firmware and checked address traces with a logic analyser and my suspicion is that actually this is something to do with the interaction with the Z80 because it is reading a status from the shared memory and then using that to set the status lights. I have been unable so far to work out where in the ROMs the Z80 code lives or where in the 8088 code it transfers it to the shared memory to allow the Z80 to run. Can anyone tell me where the Z80 firmware is in the ROMs? And does anyone have any insight into the above error or have details of the interaction between the Z80 and the 8088? The Technical Manual only goes so far unfortunately. Thanks Rob