SC601 v1.1 Z80 CPU module for RCBus-40pin - 2025-06-09

SC601 v1.1.1 Z80 CPU module for 40-pin RCBus

Documentation at www.scc.me.uk (small computer central)     

SC601 is a Z80 Central Processor Unit (CPU) module with clock oscillator, status LEDs, and a voltage supervisor and reset device, designed for the RCBus 40-pin.

The voltage supervisor and reset device (U5) provides a reliable power up reset. It works by holding the CPU in reset until the supply voltage reaches approximately 4.75 volts. If the system does not seem to be working, always check the supply voltage is above 4.75 volts on the PCB and that the RESET signal is a logic high voltage, typically above 4 volts. The supervisor should hold the reset low of about 0.3 seconds after the system is turned on and after the reset button is released.

The system should only include one enabled voltage supervisor, so a jumper option has been provided to connect or isolate this device. Normally, it should be connected, but if you have a supervisor on another module you may need to isolate this one.

The module incudes 11 LEDs. Three of the LEDs show power, halt and reset, while the other 8 are programmable. The programmable LEDs can be controlled by writing to port 0. They are used in various ways by different firmware and software. Uses include: self-test, progress during start up, disk activity and general outputs. Self-test can be particularly helpful if the system is not running correctly. For example, SCM will use these even if the system has no working RAM and no working serial port.