Z80 SBC 3.x with Reset circuit and 4x8k ROM selection

This design is based on a circuit from Grant Searle all credit to him for the initial circuit,  The PCB layout was by me and I I have changed the design to include;

Rom page selection to provide 4x8k blocks. Currently providing 3x MS basic versions and a version of FORTH

Reset on powerup circuit. This holds the CPU in reset for around 1 second on powerup. It also provides an open drain reset for the expansion socket.

The expansion port is now 40pin Scothern Cross compatible

A new jumper to disable onboard memory has been added, for when the expansion provides RAM/ROM

The RTS line is now connected for hardware flow control

An extra power socket.

A ground plane added to reduce cross talk etc.