Lo-tech ISA CompactFlash Adapter
Note: This board has been superseded by the Lo-tech ISA CompactFlash Adapter revision 2
The Lo-tech ISA CompactFlash Adapter is a through-hole, small form factor 8-bit ISA adapter providing a 40-pin IDE header suitable for connection to a separate IDE to CompactFlash adapter. The design had several goals:
- Ease of home assembly, by use of only through-hole components for basic operation
- Small form-factor, to enable use in machines with limited expansion slot space such as the Tandy 1000HX, Sinclair PC200 and Amstrad PC-20
- IBM Personal Computer XT System Board Slot 8 compatibility (with optional SMD components mounted on rear of PCB)
- 5V supply to IDE header key-pin, for cable-less operation of CompactFlash adapters supporting this power option
The board is programatically identical to the XT-CF-lite and is therefore powered by the XT-IDE Universal BIOS, provided through an in-system re-programmable 32KB (addressible) flash-based ROM. Since the BIOS is only 8KB, 24KB is available for other purposes, and is byte-programmable. The board can therefore function as a universal ROM board, regardless of whether the IDE decoder logic is used (or indeed populated on the PCB).
Specifications
General
- 8-bit ISA card with 40-pin IDE header
- 5V power supply:
- to IDE header key-pin (can drive micro-drives or CompactFlash cards without any external power connection)
- via 4-pin header (for direct soldered attachment of peripheral power cable)
- Basic functionality is dependent only on through-hole components
- Optional SMT components provide additional functionality:
- Line driver for external activity LEDs (30mA power budget for external LED)
- IBM Personal Computer XT System Board Slot 8 compatibility
- Low-cost flash memory chip for boot ROM, with 32KB usable
- Port-mapped IO; supports both 8- and 16-bit instructions (via partial address decoding)
- Utilises XT-IDE Universal BIOS (adapter type: 'XT-CF')
- Fixed resource allocation - IO ports 300-31Fh, ROM 32KB at C800h
PCB
Bill of Materials
Basic functionality requires only through-hole components:
| Part | Device | Package | Qty | Farnell | Mouser |
|---|---|---|---|---|---|
| IC1, IC3 | 74HCT688N | DIP-20 | 2 | 382504 | 771-74HCT688N |
| IC2 | AMIC - A29010-70F or SST39SF010 | DIP-32 | 1 | 1896595 | 804-39SF010A7CPHE |
| IC4 | 74HCT139N | DIP-16 | 1 | 382036 | 595-SN74HCT139N |
| IC5 | 74HCT245N | DIP-20 | 1 | 382279 | 595-SN74HCT245N |
| R2, R3, R5 | 10k Resistor (3.5mm) | - | 3 | 9342419 | 270-10K-RC |
| R4 | 5k6 Resistor (3.5mm) | - | 1 | 9343369 | 270-5.6K-RC |
| C1..5 | 0.1uF Ceramic Capacitor | C025-030X050 | 5 | 1100533 | 581-SR205E104MAR |
| C6 | 10uF Electrolytic Capacitor | E2-5 | 1 | 8767084 | 647-UVR1C100MDD |
| HD1 | T821140A1S100CEU | 2x20 Pin Header, 2.54mm spacing | 1 | 2215314 | 517-D2540-6002-AR |
| IC Socket | - | DIL32 | 1 | 1654375 | 571-1-390263-2 |
| JP1, JP2, LED | AMP - 826629-6 | 1x6 Pin Header (cut for each header) | 1 | 3418327 | 571-826629-6 |
For IBM Personal Computer XT System Board Slot 8 compatibility and device activity LED, also populate these optional components:
| Part | Device | Package | Qty | Farnell | Mouser |
|---|---|---|---|---|---|
| U1 | MC74ACT02DG | SOIC-14 | 1 | 1607770 | 863-MC74ACT02DG |
| U2 | SN74AHC1G125DBVT | SOT-23 | 1 | 1105921 | 595-SN74AHC1G125DBVT |
| R1 | RESISTOR, 0.125W 1% 130R | - | 1 | 9342567 | 270-130-RC |
| R6 | RESISTOR, 10K, 125MW | 0805 | 1 | 1612522 | 71-CRCW0805J-10K-E3 |
| C7 | CAPACITOR, 0.1UF, 50V | 0805 | 1 | 2112751 | 581-ESD55C104K4T2A24 |
- Board design permits the use of a range of DIP-32 flash chips (1, 2 or 4Mb):
- SST39SF0x0A (SST39SF010A, SST39SF020A, SST39SF040A)
- AMIC A29010
- Regardless of the chip used, 32KB is presented commencing C800h
Configuration
- JP1: ROM enable (closed = enabled)
- JP2: Slot-8 function enable (closed = enabled)
An external LED can be attached to the 2-pin LED header only if the optional components (on the rear of the PCB) are populated. JP2 also depends on those components. Current limit for LED is 30mA.
The IO port address (300h - 31Fh) is fixed, as is the ROM address (32KB at C800h).