8-bit ISA interface for Compact Flash cards with a single PLD
XT-CF-Pico is a remake of Sergey Kiselev [xt-cf-lite-v4] efectively reverting glue logic IC back to PLD but still using through hole components. This card allows connecting a Compact Flash (CF) card to computers with ISA bus and using it as a mass storage device. The card also supports BIOS extension ROM, but if you have it e.g. in a network adapter already, it's safe to leave it out.
- 16 KiB EEPROM (28128) with either 8 or 16k images, no flash ROM.
- no jumpers, everything you configure in the PLD (GAL20V8, still available on Aliexpress, used in projects like C64 PLA20V8)
This is my first ISA board and first PLD design, it was easy to debug by just rewriting the GAL and EPROM! My motivation was that there were too many components and a lot of unused pins on Sergey's design.
The idea was to use a minimum amount of components that were available late '80s, keeping Sergey's concept of having them all through hole (except of course the CF adapter). Result was one GAL IC and one EPROM.
Download latest bios from https://www.xtideuniversalbios.org/binaries/ (I used IDE_ATL.BIN) and configure primary IDE (with xtidecfg.com) for XT CF BIU 8 (I used addr 0x300). XTCFG
| Component Type | Reference | Description | Quantity | Possible Sources and Notes |
|---|---|---|---|---|
| PCB | XT-CF-Pico | 1 | jlpcb | |
| Capacitor | C1 | 0.1 uF ceramic, 5.0 mm lead spacing | 1 | |
| Capacitor | C2 | 10 uF electrolytic, 6.3 mm lead spacing | 1 | |
| LED | D1 | 5 m (T-1) LED indicator | 1 | You can use 2 pin jumper holder for external led |
| Connector | P1 | Compact Flash Card connector | 1 | 101D-TAAA-R01 from ATTEND (this was the cheapest now, footprint was updated) |
| Resistor | R1 | 470 Ohm, 1/4 W | 1 | Mouser 291-470-RC |
| Resistor | R3 | 1 kOhm, 1/4 W | 1 | Mouser 291-1K-RC |
| Resistor | R4 | 5.6 kOhm, 1/4 W | 1 | Mouser 291-5.6K-RC |
| Resistor | R2 | 10 kOhm, 1/4 W | 0 | Note: Do not install, kept for historic reasons only (card present detection?) |
| IC | U1 | 27128 EEPROM | 1 | mbm27128 |
| IC Socket | U1 | 28 pin 600 mil (wide) DIP socket | 1 | optional |
| IC Socket | U2 | 24 pin 300 mil (narrow) DIP socket | 1 | optional |
- PCB - 4.17 USD including shipping jlpcb
- GAL20V8 - 3.47 USD including shipping aliexpress
- 28C128 - 5.49 USD including shipping aliexpress
- 101D-TAAA-R01 attend - 10.4 including shipping from tme
- passives - 1USD or less (you can order them from tme to save on shipping)
Results a cost of around 5 USD per board (not including labor to assemble and program)