Real Time Clock for your PC XT. Very low profile, simple and open hardware.
| 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
| Position | Description |
|---|---|
| open (default) | Normal operation |
| closed | Clear NVRAM memory |
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 |
The board is supported by the DSCLOCK.SYS DOS driver, the 8088 BIOS, and the GLaTICK BIOS Extension.
DSCLOCK.SYS is an MS-DOS / PC DOS clock driver for DS12885 and DS12887 based real time clock controllers.
Add the following line to the CONFIG.SYS to use this driver:
DEVICE=[PATH]DSCLOCK.SYS [PORT] [/D]
Where:
- PATH - Drive and path to the driver, e.g., C:\DRIVERS\
- PORT - Decimal or hexadecimal port number. Use C notation (0x) for hexadecimal numbers, e.g., 0x240
- /D - DST enable flag. If enabled, the RTC controller will automatically adjust the clock for daylight saving time. Note that DS12885/DS12887 support North American DST switch rules, so it is not very useful for the rest of the world
Usage example:
DEVICE=C:\DRIVERS\DSCLOCK.SYS 0x240
- 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
- No known issues
- None so far
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.
