2 layers83.3 × 68.2 mm
4 layers83.3 × 68.2 mm
Yet another 8bit Retro Computer
- Size
- 83.3 × 68.2 mm
- Copper layers
- 4
- Thickness
- 2.61 mm
- Parts
- 15
- Nets
- 121
- Pads
- 328
- Tracks, vias
- 356, 136
- Pours
- 2
- Routed
- Yes
- KiCad
- KiCad 8.0 (file 20240108)
- Created
- 28 May 2024
- Updated
- 26 Jul 2024
Overview
RAM is an open-source printed circuit board by Synthron, from the Synthron/S65 repository on GitHub. It is a 4-layer board of 83.3 × 68.2 mm with 15 parts on 121 nets, routed with 356 tracks and 136 vias.
It is built around the 74HC138 and AS6C4008-55PCN. Its parts include 4 capacitors, 3 ICs and 1 connector. It belongs with the retro computing and games boards of this library.
Main components
2
74HC138
SOP-160℃~+70℃ 24ns@5.0V,16pF 2V~6V 3/8 5.2mA 5.2mA 5uA 74HC Decoder Reverse function Single Supply SOP-16 Signal Switches, Multiplexers, Decoders ROHSGRSignal Switches, Multiplexers, Decoders
AS6C4008-55PCN
PDIP-320℃~+70℃ 2.7V~5.5V 30mA 4Mbit 4uA 55ns Parallel Port (Parallel) PDIP-32 SRAM ROHSAlliance MemorySRAM
README
README.mdS65xx Computer System
Yet another 8bit Retro Computer
Completely bloated, overkill and fully hackable!
ToDo
- Finish Hardware
- Software
- WozMon
- Implement Serial IO
- Implement Input Buffer
- extended for block write
- Kernel Functions
- General SysCalls
- Hardware Drivers
- RAM-Kernel
- Basic
- EhBasic
- File System
- Operating System
- WozMon
- Hardware
- order PCBs
- order parts
- solder together
Hardware
- Modules
- Backplane Bus
- CPU
- ROM
- RAM
- Bank/IRQ
- LCD/IRQ
- SIO
- PIO
- User Ports
- IDE
- Simple-IDE
- CF
- SID
- Addr + RTC + Clock
- Prototyping Board
- LPT Interface
- MyCPU Graphics Unit Interface
Software Brainstorm
- EhBasic
- maybe Microsoft Basic? See Ben Eater
- both in different banks
- maybe Microsoft Basic? See Ben Eater
- WozMon Main Boot
- Serial Program Bootloader
- File System (FAT?)
- DOS-Like UI
boot routine:
- selftest
- RAM Check
- ROM Check + version
- Load Kernel functions to RAM
- Start Monitor
Memory Map
General:
| Start | End | Usage | Size |
|---|---|---|---|
| 0000 | 7FFF | RAM | 32.768 |
| 8000 | BEFF | RAM Banked | 16.128 |
| BF00 | BFFF | IO Space | 256 |
| C000 | FFFF | ROM Banked | 16.384 |
IO Space:
| Start | End | Usage | Size |
|---|---|---|---|
| BF00 | BF07 | Bank & IRQ | 8 |
| BF08 | BF0F | TPI IDE | 8 |
| BF10 | BF12 | LPT | 2 |
| BF13 | BF14 | --- (LPT2) | 2 |
| BF14 | BF16 | MyCPU VGA | 3 |
| BF17 | BF1B | --- | 5 |
| BF1C | BF1F | PIA LEDs | 4 |
| BF20 | BF2F | VIA 1 LCD IRQ | 16 |
| BF30 | BF3F | VIA 2 | 16 |
| BF40 | BF4F | VIA 3 | 16 |
| BF50 | BF53 | ACIA 1 | 4 |
| BF54 | BF57 | ACIA 2 | 4 |
| BF58 | BF5B | --- (ACIA 3) | 4 |
| BF5C | BF5F | --- (ACIA 4) | 4 |
| BF60 | BF7F | SID 8580 | 32 |
| BF80 | BF87 | Simple IDE | 8 |
| BF88 | BF8F | CF Card | 8 |
| BF90 | BF9F | RTC | 16 |
| BFA0 | BFFF | --- | 96 |
Interrupts
The TPI Chip for the memory banks also functions as a priority interrupt controller, providing 5 seperate interrupt lines.
IRQ_0 is further divided into 8 lines for communication modules, giving an overall of 14 available IRQ-Lines.
These are currently used as follows:
- IRQ -> TPI
- IRQ_0 -> VIA0
- IRQ_0.0 -> ACIA0
- IRQ_0.1 -> ACIA1
- IRQ_0.2 -> ACIA2
- IRQ_0.3 -> ACIA3
- IRQ_0.4 -> RTC
- IRQ_0.5 -> ---
- IRQ_0.6 -> ---
- IRQ_0.7 -> ---
- IRQ_1 -> VIA1
- IRQ_2 -> VIA2
- IRQ_3 -> ---
- IRQ_4 -> ---
- IRQ_0 -> VIA0
- NMI -> ---
Note that the NMI is connected to a push button on the bus board.
Parts
15| Qty | Value | Footprint | References |
|---|---|---|---|
| 3 | 100n | Capacitor_SMD:C_0805_2012Metric | C1, C2, C3 |
| 1 | 10µ | Capacitor_THT:CP_Radial_D5.0mm_P2.50mm | C4 |
| 1 | 74HC138 | Package_DIP:DIP-16_W7.62mm | U4 |
| 1 | AS6C4008-55PCN | Package_DIP:DIP-32_W15.24mm | U1 |
| 1 | Bus_PCI_6502 | Connector_PCBEdge:BUS_PCI | J1 |
| 1 | CY62256-70PC | Package_DIP:DIP-28_W15.24mm | U2 |
| 1 | LOGO | Eigene:logo | G*** |
| 1 | OE_H | Jumper:SolderJumper-2_P1.3mm_Bridged_RoundedPad1.0x1.5mm | JP1 |
| 1 | OE_L | Jumper:SolderJumper-2_P1.3mm_Bridged_RoundedPad1.0x1.5mm | JP2 |
| 1 | Val** | Eigene:ladder_4 | Ref** |
The 12 most common of 15 parts.
Questions
How big is the RAM PCB?
It measures 83.3 × 68.2 mm and has 4 copper layers, 2.61 mm thick.
What parts does the RAM use?
15 parts, built around the 74HC138 and AS6C4008-55PCN. 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 RAM KiCad files?
From the Synthron/S65 repository on GitHub, at the commit this page was made from: the board is Hardware/modules/RAM/RAM.kicad_pcb and its schematic Hardware/modules/ACIA2/ACIA2.kicad_sch. PCBKit opens the board in the browser, with nothing to install.
Can I use the RAM design in my own project?
Its repository states no licence, so its author keeps all rights: ask Synthron before reusing the design.
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