I am building a Z80 computer
May 20, 2013
May 20, 2013
I am building a Z80 computer, based on the Zilog Z80 Z84C0006, a 6MHz CMOS version. bdk6 has started a very similar project at nearly the same time, We will certainly exchange ideas along the way. Other than bdk6 I will build a modular system with several extension boards, and my version will probably run Microsoft BASIC later. Much later...
As I have never built a Z80 computer before I will start with a bare minimum version, devided in 3 mile stones respectively boards:
Board one (200 x 150 mm perfboard) will carry the CPU, the ROM (EEPROM), oscillator(s), reset, PIO and power supply circuitry. There is enough place left to add serial access, RAM and other fancy stuff later.
Board two (150 x 100 mm perfboard) will carry 7-segment displays with according drivers and control circuitry to display current data and address bus status.
Board three will be a kind of homebrew Arduino shield EEPROM programmer (I am too lazy to move a lot of DIP SPST switches).
Next steps will be to draw the schematics of each board and gather parts.
May 23, 2013
I managed to finish the bare bone version schematic of the Z80 computer for first experiments. I mainly followed the instructions and explanations on The First Great Z80 Project, beside studying all the data sheets. The computer is in the moment just clocked by a 1 Hz Schmitt trigger inverter oscillator, later it will be clocked by a 6.144 MHz OSC.
The next step was to make a kind of wiring plan for the address and data bus. You can find the wiring plan in the attachments. As I have no wire wrap equipment and I am not a fan of cable spaghetti, I desided to put the address and data bus wires on the top side of the board. The chips and wires are aligned at a grid of 2.54mm. I have also included the RAM already on my wiring plan; I will just leave the IC socket blank in the moment. The connection dots in the wiring plan are actually single male pin headers, so it's easy to connect several wires on one spot and have access to every address and data line with a logic probe etc. This makes the board bigger than it must be, but it hopefully helps to keep track and I can later route a PCB if this ever goes beyond experiment and prototype status.