2 layers68.6 × 53.3 mm
2 layers99.5 × 70 mm
Zed-80
Gnardisitor/zed-80Simple Z80 computer based on Grant Searle's Z80 computer.
- Size
- 99.5 × 70 mm
- Copper layers
- 2
- Thickness
- 1.6 mm
- Parts
- 33
- Nets
- 67
- Pads
- 268
- Tracks, vias
- 584, 52
- Pours
- 2
- Routed
- Yes
- KiCad
- KiCad 10.0 (file 20260206)
- Created
- 22 Dec 2025
- Updated
- 5 May 2026
Overview
Zed-80 is an open-source printed circuit board by Gnardisitor, from the Gnardisitor/zed-80 repository on GitHub. It is a 2-layer board of 99.5 × 70 mm with 33 parts on 67 nets, routed with 584 tracks and 52 vias.
It is built around the CH340C, 74HCT04D and 74LS32SC, with the AT28C256-15PU and TYPE-C-31-M-12 among its other parts. Its parts include 10 capacitors, 7 resistors, 7 ICs, 1 diode and 1 connector.
Main components
5
CH340C
SOP-16-20℃~+70℃ 2Mbps 3.3V、5V 50uA 7mA Transceiver USB 2.0 SOP-16 USB Converters ROHSWCH (Nanjing Qinheng Microelectronics)USB Converters
74HCT04D
SO-14-40℃~+125℃ 1 19ns@4.5V,50pF 2V 2uA 3.7V 4.5V~5.5V 400mV 4mA 4mA 6 74HCT 800mV SO-14 Inverters ROHSNexperiaInverters
74LS32SC
-- Logic Gates ROHSTexas InstrumentsLogic Gates
AT28C256-15PU
PDIP-28-40℃~+85℃ 10 Years 100,000 cycles 10ms 256Kbit 4.5V~5.5V Hardware write protection function、Software write protection function、Built-in error correction code (ECC) function Parallel Port (Parallel) PDIP-28 EEPROM ROHSMicrochip TechnologyEEPROM
TYPE-C-31-M-12
SMD-30℃~+80℃ 1 10,000 cycles 16P 20V 5A 7.35mm Female Surface Mount, Right Angle Type-C SMD USB Connectors ROHSHRO ElectronicsUSB Connectors
README
README.mdzed-80
Simple Z80 computer based on Grant Searle's Z80 computer.
Board
The first iteration of the board had an issue with the clock circuit since I used a 74LS04, which is a non-CMOS IC. The modified Pierce oscillator circuit I made does not function with non-CMOS inverters.
With a modified resistor configuration and a 74HCT04 inverter, I did manage to get a stable clock. However, the UART IC never let the CTS pin to low, therefore never sending any data. Without a logic analyzer, I am unable to check whether the IC, circuit, or the assembly code is bad.
Another issue with my attempt to make this board very quickly is that I based my design almost completely on Grant Searle's Z80 design and used his ported code directly, which gives me less room for making my own changes. For the next version I will base it more on my own design and try the modular ROMWBW firmware instead, which should give me more chances to modify it for my own needs.
Programmer
The programmer is based on the TommyPROM project, but I turned it into an Arduino Uno shield, which makes it more compact and easy to use. However, my version is limited to flashing only the AT28C256, which makes it much less useful for other projects. For future endeavors, I will most likely buy an XGecu T48 programmer to remove extra points of failure.
Parts
33| Qty | Value | Footprint | References |
|---|---|---|---|
| 8 | 0.1 µF | Capacitor_THT:C_Disc_D5.0mm_W2.5mm_P5.00mm | C203, C204, C301, C302, C303, C401, C402, C403 |
| 4 | M3 | MountingHole:MountingHole_3.2mm_M3_Pad_Via | MH101, MH102, MH103, MH104 |
| 2 | 1 kΩ | Resistor_THT:R_Axial_DIN0207_L6.3mm_D2.5mm_P7.62mm_Horizontal | R202, R403 |
| 2 | 10 kΩ | Resistor_THT:R_Axial_DIN0207_L6.3mm_D2.5mm_P7.62mm_Horizontal | R203, R204 |
| 2 | 22 pF | Capacitor_THT:C_Disc_D5.0mm_W2.5mm_P5.00mm | C201, C202 |
| 2 | 5.1 kΩ | Resistor_THT:R_Axial_DIN0207_L6.3mm_D2.5mm_P7.62mm_Horizontal | R401, R402 |
| 1 | 1 MΩ | Resistor_THT:R_Axial_DIN0207_L6.3mm_D2.5mm_P7.62mm_Horizontal | R201 |
| 1 | 7.3728 MHz | Crystal:Crystal_HC49-4H_Vertical | Y201 |
| 1 | 74HCT04 | Package_DIP:DIP-14_W7.62mm_Socket_LongPads | U201 |
| 1 | 74LS32 | Package_DIP:DIP-14_W7.62mm_Socket_LongPads | U301 |
| 1 | AT28C256-15PU | Package_DIP:DIP-28_W15.24mm_Socket_LongPads | U302 |
| 1 | CH340C | Package_SO:SOIC-16_3.9x9.9mm_P1.27mm | U401 |
| 1 | HM628128BLP-10 | Package_DIP:DIP-32_W15.24mm_Socket_LongPads | U303 |
| 1 | LED | LED_THT:LED_D5.0mm | D401 |
| 1 | LOGO | code:qr | G*** |
| 1 | MC68B50P | Package_DIP:DIP-24_W15.24mm_Socket_LongPads | U402 |
| 1 | SW_Push | Button_Switch_THT:SW_PUSH_6mm | SW201 |
| 1 | TYPE-C-31-M-12 | Connector_USB:USB_C_Receptacle_HRO_TYPE-C-31-M-12 | J401 |
| 1 | Z84C0010PEC | Package_DIP:DIP-40_W15.24mm_Socket_LongPads | U202 |
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Questions
How big is the Zed-80 PCB?
It measures 99.5 × 70 mm and has 2 copper layers, 1.6 mm thick.
What parts does the Zed-80 use?
33 parts, built around the CH340C, 74HCT04D, 74LS32SC and AT28C256-15PU. The full list of its parts is on this page, with links to each part's symbol and footprint where PCBKit's library has them.
Where can I download the Zed-80 KiCad files?
From the Gnardisitor/zed-80 repository on GitHub, at the commit this page was made from: the board is boards/zed-80/zed-80.kicad_pcb and its schematic boards/prom-shield/prom-shield.kicad_sch. PCBKit opens the board in the browser, with nothing to install.
Can I use the Zed-80 design in my own project?
Its repository states no licence, so its author keeps all rights: ask Gnardisitor before reusing the design.