So, I took another slight diversion and built a piece of test equipment that can help.
The analyser can connect to the set of control signals that control a shift register chain within a project, and display on several bar-LED displays, the status of the shift register chain being monitored.
The unit has two inputs so it can monitor two shift register chains in parallel, each of up to 56 bits, or by flicking a switch, combine the two displays together to monitor a single chain of up to 112 bits in length. The project is extendable and could be expanded to monitor shift register chains of any number of bits if required.
The unit is a bit of a compromise as I had to use parts and a case I had available, but it does employ fully buffered inputs so presents minimal external load to the project it’s being used to monitor, and has it’s own internal voltage regulator board which will accept a 9v AC/DC input. With all the LED's on, the unit draws just under an amp !!
At some point over the next few days, I’ll create a basic construction article and include the PCB foils and circuit diagrams etc.