Device for loading and reading strings of latches in a data processing system

A device for loading data in and reading data out of latch strings located in field replaceable units containing the circuitry of a data processing system realized in accordance with the Level-Scan Sensitive Design (LSSD) technique. Each field replaceable unit includes an addressing circuit. The addressing circuits are interconnected by a monitoring loop over which a configuration of address bits is serially transmitted by a control circuit. The data to be loaded and read out propagate in a data loop and are entered in a latch string under control of the addressing circuit.