ISA-WS-SL811 is a simple 8-bit ISA (or XT) bus adapter for the Waveshare SL811 USB board, made for debugging and development purposes in the course of the TC-USB project mainly. It is based upon an identity comparator (74'688 or 74'521), an inverter (74'14) and a 3.3V regulator. The ISA data and IRQ lines are directly connected to the SL811 without an additional bus transceiver, so its drive current (4 mA) does not meet ISA specification (24 mA). This is not a problem in most cases, as ISA busses are not fully loaded usually and CMOS inputs are all over the place even in "old" machines. And ISA-based PC/104 also specifies 4 mA...
I/O port address (0x000 to 0x3fc) and IRQ channel (3, 4, 5, 6, 7, 9) can be configured by DIP switch and jumper, respectively. Three LEDs indicate reset, I/O and interrupt status. A dedicated pin header provides a buffered (100nF + 220uF capacitors) +5V power supply suitable for Waveshare's separate USB VBUS. The Waveshare board fits into an angled socket header and can optionally be fastened on matching holes.
The boards are available through OSH Park as a shared project (see BoM below), the schematic can be downloaded from here. Possible parts are also given, but can be substituted with matching alternatives.
| Amount | Val. | Pkg. | Ref. | Descr. | Manuf. | Type |
|---|---|---|---|---|---|---|
| 1 | ISA-WS-SL811 PCB | OSH Park | ISA-WS-SL811 | |||
| 1 | Waveshare SL811 USB Board | Waveshare | SL811 USB Board | |||
| 1 | Jumper Wire Female/Female | |||||
| 3 | 100n 50V X7R | Cap 5mm | C1, C2, C3 | Ceramic Capacitor | Vishay | K104K10X7RF5UH5 |
| 1 | 220µ 10V | 6.3x11mm 2.5mm | C4 | Electrolytic Capacitor (low ESR) | Rubycon | 10ZL220M6.3X11 |
| 3 | 10µ 16V X7R | Cap 5mm | C5, C6, C7 | Ceramic/Tantal Capacitor | TDK | FK26X7R1C106K |
| 1 | Red | LED 3mm | DS1 | LED | Würth Elektronik | 151031SS06000 |
| 1 | Green | LED 3mm | DS2 | LED | Würth Elektronik | 151031VS06000 |
| 1 | Yellow | LED 3mm | DS3 | LED | Würth Elektronik | 151031YS05900 |
| 1 | SH 2x10 90° .1" | J1 | 2x10 Angled Socket Header | Würth Elektronik | 613020243121 | |
| 1 | PH 2x6 .1" | J2 | 2x6 Pin Header | |||
| 1 | PH 2x1 90° .1" | J3 | 2x1 Angled Pin Header | |||
| 3 | 1k | Res 0207 | R1, R2, R3 | Resistor (match LEDs!) | ||
| 1 | 10k | SIP-9 | RN1 | Resistor Network (bussed) | Bourns | 4609X-101-103LF |
| 1 | DIP-16 | S1 | 8-Position DIP Switch | Würth Elektronik | 418127270908 | |
| 1 | DIP-20 | U1 | 8-Bit Identity Comparator (74'688 or 74'521) | Texas Instruments | SN74F521N | |
| 1 | DIP-20 | DIP-20 Socket | Assmann | A 20-LC-TT | ||
| 1 | DIP-14 | U2 | Hex Schmitt-Trigger Inverter (74'14) | Texas Instruments | SN74ACT14N | |
| 1 | DIP-14 | DIP-14 Socket | Assmann | A 14-LC-TT | ||
| 1 | TO-92 | U3 | 3.3V LDO voltage regulator | Microchip | MCP1700-3302E/TO |
