The first “real” board for the RetroSys2019 system is the Z80 CPU board. Compared to older/other designs it has some specifics :
- A DIL crystal oscillator. In the past I had quite some issues with crystals mixed with modern TTL creating unstable clock signals. A DIL crystal oscillator will fix this and when using a socket at the same time gives the opportunity to play with the clock speed without soldering.
- Fully buffered bus. Which not only buffers the CPU signals (increasing the fan-out) but also giving the opportunity to put the CPU board in “Tri-State” , making the bus available for another processor, e.g. an Arduino to write the memory.
- A decent (TL7705) reset signal generator.
The board as it appears in Kicad (Non-Rendered and Rendered versions) :
DISCLAIMER : Please note that these boards have only been designed VERY recently . They are currently being manufactured and I will post progress in my blog.