ISA 8-bit Backplane
April 2, 2020 ยท View on GitHub
Compact ISA 8-bit Backplane board
Introduction
This backplane was designed as a smaller version of Micro ATX ISA Backplane. It can be used to build a compact IBM PC/XT compatible system using the Micro 8088 processor board, and the 8-bit ISA cards that I've designed: ISA Super VGA, ISA Floppy Disk and Serial Controller, XT-CF-Lite, ISA OPL2.
Specifications
- 7 ISA 8-bit (62 pin) slots
- ATX power supply connector, and ATX power control circuit
- Bi-color activity LED, that changes the color when the processor is executing the code (the color changes every time A7 address line changes its value)
- The form factor is (mostly) compatible with ATX / Micro ATX
- Pads for optional termination resistors
Hardware Documentation
Schematic and PCB Layout
Building Insturctions
Please refer to Building Instructions page for detailed instructions.
Jumpers, Connectors, and Switches
P1 - ATX power connector
| Pin | Description | Pin | Description |
|---|---|---|---|
| 1 | +3.3V power supply (not used) | 11 | +3.3V power supply (not used) |
| 2 | +3.3V power supply (not used) | 12 | -12V power supply |
| 3 | GND | 13 | Ground |
| 4 | +5V power supply | 14 | Power supply ON signal |
| 5 | Ground | 15 | Ground |
| 6 | +5V power supply | 16 | Ground |
| 7 | Ground | 17 | Ground |
| 8 | Power good (not used) | 18 | -5V power supply (not used)* |
| 9 | +5V standby power supply | 19 | +5V power supply |
| 10 | +12V power supply | 20 | +5V power supply |
Note: -5V is not provided by most ATX power supplies. It is generated using an on board voltage regulator instead
P2 - Power Switch connector
| Pin | Description |
|---|---|
| 1 | Ground |
| 2 | Power ON signal |
P3 - Power LED connector
| Pin | Description |
|---|---|
| 1 | LED+ |
| 2 | Ground |
SW1 - Power Switch
Press SW1 to turn power on or off. The SW1 is connected in parallel with P2
Bill of Materials - Version 1.0
ISA 8-bit Backplane project on Mouser.com - View and order all components except of the PCB.
ISA 8-bit Backplane project on OSH Park - View and order the PCB.
| Component type | Reference | Description | Quantity | Possible sources and notes |
|---|---|---|---|---|
| PCB | ISA 8-bit Backplane PCB - Version 1.0 | 1 | Refer to the RetroBrew Computers Board Inventory page for ordering information, or order from a PCB manufacturer of your choice using provided Gerber or KiCad files | |
| Integrated Circuit | U1 | 74HCT74, DIP-14 package | 1 | Mouser 595-SN74AHCT74N |
| Integrated Circuit | U2 | 74HCT14, DIP-14 package | 1 | Mouser 595-SN74AHCT14N |
| Integrated Circuit | U3 | LM7905C -5V voltage regulator | 1 | Mouser 512-LM7905CT |
| IC Socket | U1, U2 | DIP-14, 300 mil socket | 2 | Mouser 517-4814-3000-CP |
| LED | D1 | 3 mm, blue LED indicator | 1 | Mouser 696-SSL-LX3054USBD |
| LED | D2 | 3 mm, bi-color red/green LED indicator | 1 | Mouser 696-SSL-LX3054IGW |
| Diode | D3, D4 | 1N4148 | 2 | Mouser 512-1N4148 |
| Tactile Button | SW1 | 6 mm tactile button, straight | 1 | Mouser 653-B3F-1000 |
| Connector | P1 | 20 pin ATX power connector | 1 | Mouser 538-46015-2006 |
| Connector | P2, P3 | 4 pin header, 2.54 mm pitch | 2 | Mouser 649-68002-104HLF |
| Connector | BUS1-BUS7 | 62 pin card edge connector, 2.54 mm pitch | 7 | Mouser 571-6-5530843-5 |
| Capacitor | C1 - C19 | 10 uF, 16V, MLCC, 5 mm lead spacing | 19 | Mouser 810-FG28X5R1E106MR06 |
| Capacitor | C20 | 1 uF, MLCC, 5 mm lead spacing | 1 | Mouser 810-FG28X5R1H105KRT0 |
| Capacitor | C21, C22 | 0.1 uF, MLCC, 5 mm lead spacing | 2 | Mouser 594-K104K15X7RF53H5 |
| Resistor | R1, R2 | 10 kohm, through hole | 2 | Mouser 291-10K-RC |
| Resistor | R3 | 1 kohm, through hole | 1 | Mouser 291-1K-RC |
| Resistor | R4 - R7 | 470 ohm, through hole | 4 | Mouser 291-470-RC |
| Resistor Array | RR1 - RR5 | do not populate | Optional, should not be populated |