iButton / 1-Wire family code reference table
Use family codes as a first check of a 1-Wire ROM format, then verify the exact part, documentation and device behaviour. A printed ID alone cannot identify a manufacturer or prove compatibility.
| Family code | Part number | Device type |
|---|---|---|
01h | DS1990A / DS2401 / DS2411 | 64-bit ROM serial number — the standard access credential |
02h | DS1991 | MultiKey, three password-protected subkeys |
04h | DS1994 / DS2404 | 4 Kb NV RAM plus real-time clock |
06h | DS1993 | 4 Kb NV RAM |
08h | DS1992 | 1 Kb NV RAM |
09h | DS1982 / DS2502 | 1 Kb add-only EPROM |
0Ah | DS1995 | 16 Kb NV RAM |
0Bh | DS1985 / DS2505 | 16 Kb add-only EPROM |
0Ch | DS1996 | 64 Kb NV RAM — the large-memory token |
0Fh | DS1986 / DS2506 | 64 Kb add-only EPROM |
10h | DS1920 / DS18S20 | Temperature sensor |
14h | DS1971 / DS2430A | 256-bit EEPROM |
1Ah | DS1963L | Monetary iButton with write cycle counters |
1Dh | DS2423 | 4 Kb NV RAM with external counters |
21h | DS1921 Thermochron | Temperature logger with clock and memory |
23h | DS1973 / DS2433 | 4 Kb EEPROM |
24h | DS1904 / DS2415 | Real-time clock |
26h | DS2438 | Smart battery monitor |
28h | DS18B20 | Temperature sensor — the most common 1-Wire sensor |
2Dh | DS1972 / DS2431 | 1 Kb EEPROM |
33h | DS1961S / DS2432 | 1 Kb EEPROM with SHA-1 authentication |
41h | DS1922 / DS1923 | High-resolution temperature / humidity logger |
This table is provided as a working reference. For design-critical decisions always confirm against the current manufacturer datasheet.
On an original DS1990A, the ROM combines a family code, serial number and CRC. Confirm how your reader displays the bytes and compare its readout with the supplied part documentation. Markings and a valid CRC do not prove manufacturer origin or that the ID is unique across supplied batches.
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