Radio 86RK - ROM Cartridge
June 15, 2022 ยท View on GitHub
ROM cartridge for my Radio-86RK implementation
Introduction
This ROM cartridge provides 16 KiB - 32 KiB ROM, that can be used to store the software - development tools, games, and so on. The ROM cartridge connects to Radio-86RK using the 8255 PPI based parallel interface.
Using ROM Cartridge
Make sure to power off the computer before connecting the cartridge. Connect the cartridge to the computer using a 26 conductor flat ribbon cable.
The Radio-86RK ROM monitor provides R command that can be used to copy of the ROM cartridge to computer's RAM. The syntax of R command is: R<ROM_Start_Address>,<ROM_End_Address>,<Destination_Start_Address>
The ROM monitor also provides a subroutine to copy ROM cartridge content to the RAM:
- Entry point: 0FA68H
- Input registers:
- HL - ROM start address
- DE - ROM end address
- BC - RAM start address
Hardware Documentation
Schematic and PCB Layout
Connectors and Jumpers
J1 - Parallel Port Connector
| Pin | Description | Pin | Description |
|---|---|---|---|
| 1 | Output: A8 | 2 | Output: D0 |
| 3 | Output: A9 | 4 | Output: D1 |
| 5 | Output: A10 | 6 | Output: D2 |
| 7 | Output: A11 | 8 | Output: D3 |
| 9 | Output: A12 | 10 | Output: D4 |
| 11 | Output: A13 | 12 | Output: D5 |
| 13 | Output: A14 | 14 | Output: D6 |
| 15 | Output: /ROM_CE | 16 | Output: D7 |
| 17 | Output: A7 | 18 | Input: A0 |
| 19 | Output: A6 | 20 | Input: A1 |
| 21 | Output: A5 | 22 | Input: A2 |
| 23 | Output: A4 | 24 | Input: A3 |
| 25 | Power: +5V | 26 | Power: GND |
JP1 and JP2 - ROM Type Configuration
JP1 determines the connection of the ROM's pin 1, while JP2 determines the connection of the ROM's pin 27
| ROM Type | Jumper 1 Position | Jumper 2 Position |
|---|---|---|
| 27C128 | JP1 - 2-3 | JP2 - 1-2 (jumper installed) |
| 27C256, 29C256 | JP1 pin 1 to JP2 pin 1 | JP1 pin 2 to JP2 pin 2 |
| 28C256, NVRAM | JP1 - 1-2 | JP2 - 1-2 (jumper installed) |
Bill of Materials
-
Radio-86RK-ROM project on Mouser.com - View and order all component except of the PCB.
-
Unicorn Electronics is a good source for UV ERPROMs and EEPROMs
| Component type | Reference | Description | Quantity | Possible sources and notes |
|---|---|---|---|---|
| PCB | Radio-86RK ROM Cartridge PCB - Version 1.1 | 1 | Buy from my Tindie store: Radio-86RK - PCB or order from a PCB manufacturer of your choice using provided Gerber or KiCad files | |
| Capacitor | C1 | 0.1 uF, MLCC, 5 mm Pitch | 1 | Mouser 594-K104K15X7RF53H5 |
| Connector | J1 | 13x2 pin header, shrouded | 1 | Mouser 517-30326-6002 |
| Connector | JP1 | 3 pin header | 1 | Mouser 855-M20-9990345 |
| Connector | JP2 | 2 pin header | 1 | Mouser 855-M20-9990245 |
| Integrated Circuit | U1 | 28C256, 27C256, 27C128 | 1 | Unicorn Electronics 27C256, 27C128, 28C256, Mouser 556-AT28C25615PU |
| IC Socket | U1 | 28 pin DIP | 1 | Mouser 649-DILB28P223TLF, 517-4828-6000-CP |
| Connector | Cable Assembly | 13x2 pin IDC socket | 2 | Mouser 517-D89126-0131HK |
| Cable | Cable Assembly | 26 conductor flat ribbon cable, 1 ft. | 1 | Mouser 517-3365/26FT |