2 layers144.8 × 73.9 mm
Control
Robert-Riordan-UCD/8_Bit_CPU_PCB
PCB version of Ben Eaters 8-bit breadboard computer
68 partsCERN-OHL-P-2.0
2 layers84.3 × 39.3 mm
MemoryAccessRegister
Robert-Riordan-UCD/8_Bit_CPU_PCBPCB version of Ben Eaters 8-bit breadboard computer
- Size
- 84.3 × 39.3 mm
- Copper layers
- 2
- Thickness
- 1.6 mm
- Parts
- 26
- Nets
- 35
- Pads
- 103
- Tracks, vias
- 151, 0
- Pours
- 2
- Routed
- Yes
- KiCad
- KiCad 8.0 (file 20240108)
- Created
- 22 Jul 2024
- Updated
- 15 Jan 2025
Overview
MemoryAccessRegister is an open-source printed circuit board by Robert-Riordan-UCD, from the Robert-Riordan-UCD/8_Bit_CPU_PCB repository on GitHub, published under the CERN-OHL-P-2.0 licence. It is a 2-layer board of 84.3 × 39.3 mm with 26 parts on 35 nets, routed with 151 tracks and 0 vias.
It is built around the 74LS173SC, CD74HCT258E and SN74AC14N. Its parts include 9 resistors, 4 ICs, 4 diodes, 3 connectors and 1 capacitor. It belongs with the retro computing and games boards of this library.
Main components
374LS173SC
CDIP-160℃~+70℃ 10ns 10ns 28mA 30MHz 4 4.75V~5.25V 40ns@5V,15pF 74LS Series Asynchronous D-Type Reset Rising Edge Tri-State CDIP-16 Flip FlopsTexas InstrumentsFlip Flops
CD74HCT258E
PDIP-16-55℃~+125℃ 27ns@4.5V,50pF 4.5V~5.5V 6mA 6mA 74HCT 8uA Output enable high-impedance、Tri-state output Single Supply PDIP-16 Signal Switches, Multiplexers, Decoders ROHSTexas InstrumentsSignal Switches, Multiplexers, Decoders
SN74AC14N
PDIP-14-40℃~+85℃ 10ns@5V,50pF 2.2V~3.9V 24mA 24mA 2V~6V 2uA 4.7V 440mV 500mV~1.1V 6 6 74AC Schmitt trigger PDIP-14 Inverters ROHSTexas InstrumentsInverters
README
README.md8-Bit PCB CPU
This is my version of Ben Eaters 8-bit breadboard SAP-1 CPU, converted to a PCB. I have made some minor changes as I could not find all of the components as listed in Ben's part list.
Video of the computer running
https://youtube.com/shorts/QNcSWgcGv9o?si=QzoUVq9Kj8X1f4Rs
Major Changes
Random Access Memory
- RAM IC's have been replaced with ATMega328-PU's. This should allow me to have persistant programs between power cycles.
License
CERN Open Hardware Licence Version 2 - Permissive
Parts
26| Qty | Value | Footprint | References |
|---|---|---|---|
| 5 | 1k | _DownloadFootprints:CF_series_Resistors_THT | R5, R6, R7, R8, R9 |
| 4 | 220 | _DownloadFootprints:CF_series_Resistors_THT | R1, R2, R3, R4 |
| 4 | LED | LED_THT:LED_D5.0mm | D1, D2, D3, D4 |
| 1 | 0.1uF | Capacitor_THT:C_Disc_D5.0mm_W2.5mm_P2.50mm | C1 |
| 1 | 74LS173 | Package_DIP:DIP-16_W7.62mm | U4 |
| 1 | CD74HCT258E | _DownloadFootprints:2_to_1_selector | U2 |
| 1 | Conn_01x03_Pin | Connector_PinHeader_2.54mm:PinHeader_1x03_P2.54mm_Vertical | J3 |
| 1 | Conn_01x05_Pin | Connector_PinHeader_2.54mm:PinHeader_1x05_P2.54mm_Vertical | J1 |
| 1 | Conn_01x06_Pin | Connector_PinHeader_2.54mm:PinHeader_1x06_P2.54mm_Vertical | J2 |
| 1 | SN74AC14N | _DownloadFootprints:6x_not | U1 |
| 1 | SW_SPDT | 8BitCPUFootprints:DoubleThrowSwitch | SW1 |
| 1 | ~ | 8BitCPUFootprints:DIP-8 | U3 |
The 22 most common of 26 parts.
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Questions
How big is the MemoryAccessRegister PCB?
It measures 84.3 × 39.3 mm and has 2 copper layers, 1.6 mm thick.
What parts does the MemoryAccessRegister use?
26 parts, built around the 74LS173SC, CD74HCT258E and SN74AC14N. 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 MemoryAccessRegister KiCad files?
From the Robert-Riordan-UCD/8_Bit_CPU_PCB repository on GitHub, at the commit this page was made from: the board is MemoryAccessRegister/MemoryAccessRegister.kicad_pcb and its schematic ALU/ALU.kicad_sch. PCBKit opens the board in the browser, with nothing to install.
Can I use the MemoryAccessRegister design in my own project?
Its repository publishes it under the CERN-OHL-P-2.0 licence: you may reuse it on that licence's terms (keep the author's notice, and for a copyleft licence share your changes alike).