Z80 PUC is a single-board Z80-based computer for embedded applications.
It's designed with all through-hole components for easy soldering and hacking, as well as increased retro-cool factor. Despite its retro feel, all of its parts are still readily available and in production as of writing this.
The goal is to have a Z80 "module" that can be quickly modified and then added to a project instead of having to design and order a custom PCB every time. Kind of like using a Raspberry Pi instead of designing your own ARM-based computer for every project.
The "PUC" in Z80 PUC stands for "Previous Unit of Computing". Since the x86 CPUs in the Intel NUC (Next Unit of Computing) and the Z80 both have a common ancestor (the Intel 8080 CPU), and both the NUC and the Z80 PUC are small form factor computers, I thought it would be funny to call them something similar.
| From | To | Size | Use |
|---|---|---|---|
$0000 |
$1FFF |
8K | ROM |
$2000 |
$3FFF |
8K | Banked Area RAM |
$4000 |
$7FFF |
16K | Bus Expansion |
$8000 |
$FFFF |
32K | Static Area RAM |
The first 4 bits of Port B on the PIO select one out of 16 banks of 8K. The
static RAM area ($8000-$FFFF) is made up of 4 8K banks ($C-$F).
The total amount of addressable RAM built-in is 16x8K = 128K
- The CTC uses I/O addresses
$00-$0F. - The PIO uses I/O addresses
$10-$1F.
- The PIO gives us an additional 8 GPIO pins to play around with, 4 of which are used for memory bank selection, and 1 for the on-board LED. Implementing those without a PIO would increase component count, so since we're including it regardless, might as well use it.
- Transferring 8 bits at a time is probably faster than serial, and if pin count really is at a premium on your peripheral's microcontroller, you can still send fewer bits at a time.
- The parallel interface works regardless of the peripheral's clock speed.
- It's what I already had lying around in the parts bin.
I just included the CTC for timer interrupts. I've never needed any of the CTC's other functionality, so I decided to save some space and not include a pin header for that. If you really need it, you can just solder a few wires directly to the board, or add an external CTC chip.
- 74HC137 <=> 74HC138
- AS6C1008 <=> AS6C4008
- AT28C64 <=> AT28C256
Z80 PUC (c) by Ramy Tarchichy
Z80 PUC is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.
You should have received a copy of the license along with this work. If not, see http://creativecommons.org/licenses/by-sa/4.0/.