RTC8088
Real Time Clock for your PC XT. Very low profile, simple and open hardware.
Hardware Documentation
Schematic and PCB Layout
Swiches and Jumpers
SW1 - RTC I/O address select
| I/O Address | SW1.1 | SW 1.2 | SW 1.3 |
|---|---|---|---|
| 0x70 | OFF | OFF | OFF |
| 0x240 | ON | OFF | OFF |
| 0x2A0 | OFF | ON | OFF |
| 0x2C0 | ON | ON | OFF |
| 0x340 | OFF | OFF | ON |
| 0x3A0 | ON | OFF | ON |
| 0x3C0 | OFF | ON | ON |
| Reserved | ON | ON | ON |
- Note 1: The table above gives the addresses in the supplied SPLD fuse map. The selection can be changed by reprogramming the SPLD
- Note 2: "Reserved" address is set to 0x70 in the supplied SPLD fuse map. It is recommended to use this setting when adding a custom I/O address to the SPLD
JP1 - Clear CMOS
| Position | Description |
|---|---|
| open (default) | Normal operation |
| closed | Clear NVRAM memory |
Bill of Materials
Version 3.0
RTC8088 project on Mouser.com - View and order all components except of the FDC and the PCB.
RTC8088 on OSH Park - View and order the PCB.
| Component type | Reference | Description | Quantity | Possible sources and notes |
|---|---|---|---|---|
| PCB | RTC8088 PCB - Version 3.0 | 1 | Order from your favorite PCB manufacturer using provided Gerber files | |
| Integrated Circuit | U1 | DS12885+ - RTC, 24 pin DIP | 1 | Mouser 700-DS12885 or 700-DS12885N |
| Integrated Circuit | U2 | ATF16V8B-15PU - Simple Programmable Logic Device, 20 pin DIP | 1 | Mouser 556-AF16V8B15PU or GAL16V8 |
| Quartz Crystal | Y1 | 32768 Hz, 6 pF | 1 | Mouser 815-AB26T32768KHZ6B, 520-ECS327-6-13-X, or 628-VT200F-6PF20PPM |
| Battery Holder | BT1 | CR2032 battery holder | 1 | Mouser 122-2620-GR or 122-2420-GR |
| Battery | BT1 | CR2032 battery | 1 | Mouser 81-CR2032, 658-CR2032, or 614-CR2032-200 |
| Capacitor | C1 | 0.1 uF, 50V, MLCC, 5 mm pitch | 1 | Mouser 594-K104K15X7RF53H5 or 810-FG28X7R1H104KNT6 |
| Resistor Array | RN1 | 10 kohm, bussed, 5 pin SIP | 1 | Mouser 652-4605X-1LF-10K or 652-4605X-AP1-103LF |
| DIP Switch | SW1 | DIP switch, 3 position, SPST | 1 | Mouser 774-2103MS |
| Pin Header | JP1 | 2 pin header, 2.54 mm pitch | 1 | Mouser 649-68002-102HLF |
| Jumper | JP1 | Shunt, 2 pin, 2.54 mm pitch | 1 | Mouser 806-SX1100-B |
| IC Socket | U1 | 20 pin DIP, 2.54 mm pitch, 7.62 mm row spacing | 1 | Mouser 649-DILB20P-223TLF |
| IC Socket | U2 | 24 pin DIP, 2.54 mm pitch, 15.24 mm row spacing | 1 | Mouser 649-DILB24P-223TLF |
Software
The board is supported by the 8088 BIOS and GLaTICK BIOS Extension.
Release Notes
Changes
- Version 3.0
- Add I/O address configuration switches
- Remove IRQ configuration jumpers and IRQ support
- Version 2.0
- Aitor RTC8088
- Version 1.0
- Initial version
Known Issues
- No known issues
Wishlist
- None so far
Red Tape
Licensing
RTC8088 is an open source hardware project. The hardware design itself, including schematic and PCB layout design files are licensed under the strongly-reciprocal variant of CERN Open Hardware Licence version 2. The SPLD code is licensed under GNU General Public License v3. Documentation, including this file, is licensed under the Creative Commons Attribution-ShareAlike 4.0 International License.
