DS1982 Add-Only iButton
1 Kb add-only EPROM for records that should not be altered.
Physics does the enforcing here. This is EPROM without an erase path: per the original manufacturer's datasheet a programmed bit stays programmed, so data written to a DS1982 cannot be removed or edited through the normal 1-Wire interface. Software can supersede an old page by programming a newer one, which gives you append-only ledger behaviour, and each of the four 256-bit pages can additionally be write-protected so it accepts nothing further. Confirm the behaviour for the supplied version.
Ordering information
| MOQ | Confirmed by model and order when quoting |
|---|---|
| Preparation time | Availability and lead time are confirmed by model and order when quoting |
| Packing | Confirm pack quantity, protection and labelling for the selected model. |
| Samples | Sample quantity, fees and shipping are confirmed for the selected model. |
| Payment | Agree payment terms and the payee in the quotation and invoice. |
| Shipping | Confirm the shipping method, cost and timing for your destination and order. |
| Customization | State ROM, colour, marking and packing needs; feasibility and cost require confirmation. |
No erase path — that is the feature
A rewritable device can be altered by whoever holds it and a suitable reader. The DS1982 has no erase function, which is why it is worth considering for guard-tour checkpoints, calibration records, maintenance logs and other records that may need to show they were not edited after the fact. When an inspector asks whether the log could have been edited, "the memory has no erase function" is a useful answer, though it does not replace your own procedures and access controls. Need more room for a longer history? The DS1985 is the same idea with sixteen times the memory.
Key features
- Original DS1982 reference: 1 Kbit add-only EPROM in four 256-bit pages.
- Original EPROM programming changes bits from 1 to 0; pages can be write-protected or superseded through page redirection.
- Use a programmer that supports the documented programming voltage and sequence. Write protection does not by itself authenticate the holder.
Specifications
| Chip / compatibility | DS1982 · family code 09h · shares its die with the DS2502 chip form |
|---|---|
| Memory | 1 Kbit add-only EPROM (4 pages × 256 bits) + 64-bit status memory for page write-protect bits |
| Protocol | 1-Wire · reads at 2.8–6.0 V across −40 to +85 °C; programs at 11.5–12.0 V within −40 to +50 °C · CRC-verified programming (per the original manufacturer's datasheet; confirm for the supplied version) |
| Operating temperature | −40 to +85 °C · battery-free; data retention per the original manufacturer's datasheet (confirm for the supplied version) |
| Package | F5 can, Ø16.25 × 5.89 mm · approx. 3 g |
| Options | Colour, marking and other customization options: feasibility, MOQ and cost are confirmed in the quote. |
Product dimensions
Inside the stainless can
Typical construction of this can format: a stainless-steel shell, an insulating grommet separating lid from base, and the chip bonded inside. Lid = data contact, base = ground return. Wall thickness, grommet material and other construction details: confirm for the supplied version.
Which memory iButton do you need?
The whole memory range side by side, grouped by storage technology — capacities and family codes per the Analog Devices datasheets.
| Model | Family code | Capacity | Memory technology | Pick it for |
|---|---|---|---|---|
| DS1971 | 14h | 256 bit + 64-bit OTP | EEPROM — battery-free | Asset tag: a locked ID beside rewritable data |
| DS1972 | 2Dh | 1 Kbit (128 B) | EEPROM — battery-free | Per-page write-protect or EPROM-emulation modes |
| DS1973 | 23h | 4 Kbit (512 B) | EEPROM — battery-free | Battery-free rewritable memory (4 Kbit); production travellers |
| DS1982 | 09h | 1 Kbit (128 B) | EPROM — add-only; written data is not erasable (per datasheet) | Add-only records such as checkpoints and certificates |
| DS1985 | 0Bh | 16 Kbit (2 KB) | EPROM — add-only; written data is not erasable (per datasheet) | Append-only service history (16 Kbit) |
| DS1992 / DS1993 | 08h / 06h | 1 Kbit / 4 Kbit | NV RAM — battery-backed, high write endurance (per datasheet) | Data that changes constantly on the key |
| DS1996 | 0Ch | 64 Kbit (8 KB) | NV RAM — battery-backed, high write endurance (per datasheet) | Portable database — 64 Kbit NV RAM |
| DS1994 | 04h | 4 Kbit + RTC | NV RAM + clock, timer, counter, alarms | Time- or usage-limited access with the expiry held in the key |
| DS1904L | 24h | No user memory | Real-time clock only | Give a microcontroller a real-time timebase |
| DS1991 | 02h | 1152 bit = 3 × 384 bit | Secure NV RAM — three password zones | Legacy multi-tenant systems (not for new secure designs) |
| DS1961S | 33h | 1 Kbit + 64-bit secret | EEPROM + SHA-1 challenge–response | Authentication: proves it knows a secret (assess cloning risk for your own system) |
Typical applications
Frequently asked questions
Can data on a DS1982 really not be erased?
Per the original manufacturer's datasheet, there is no erase mechanism in the silicon; confirm for the supplied version. This is EPROM in an opaque steel can with no UV window, so a programmed bit is not meant to be returned to its unprogrammed state by any command, password or piece of equipment. Software creates an append-only ledger by superseding an old page with a newly programmed one, and each of the four pages can also be permanently write-protected so it will accept nothing further.
What voltage does programming a DS1982 need?
Per the original manufacturer's datasheet, reading works at the normal 2.8–6.0 V bus level, but programming requires a 12 V pulse on the data line, so a plain read-only reader cannot write to it; confirm for the supplied version. A 1-Wire adapter or programmer that explicitly supports EPROM devices is needed for this — check your hardware if you plan to write in the field rather than pre-programming at issue.
Related products
DS1991 MultiKey iButton
Three password-protected 384-bit subkeys in one button.
DS1992 / DS1993 Memory iButton
1 Kb and 4 Kb NV RAM tokens for carrying data on the key.
DS1996 64 Kb Memory iButton
The large-memory token — 64 Kb of rewritable NV RAM.
DS1961S SHA-1 Authentication iButton
1 Kb EEPROM with on-chip SHA-1 challenge–response.