This is essentially a redraw of Mahjongg's great ZX81plus38 project. I've done it to be able to fix and modify some issues:
- fixed pinout of tape connectors CO2/CO3
- fixed rotation/position of keyboard connector J3
- fixed CPU clock phase
- fixed position of connectors and mounting holes
- replaced USB power connector with 2.1/2.5 mm power plug
- simplified memory address decoder to allow full usage of RAM/ROM memory
- fixed video output sync latch to avoid ghost lines