DS1990A vs TM1990A vs RW1990: what is the difference?
A plain comparison of the read-only DS1990A, its TM1990A equivalent, the rewritable RW1990 blank and the universal Cyfral/Metakom blanks — what each one is for, whether it can be copied, and which readers accept it.
| Type | Rewritable | Protocol | Typical use | Notes |
|---|---|---|---|---|
DS1990A / DS1990R | No — factory-programmed, read-only | 1-Wire, 64-bit ROM | The original credential issued by system owners | Each unit carries a globally unique ID that cannot be altered. This is what makes it trustworthy as an identity token. |
TM1990A | No — read-only | 1-Wire, 64-bit ROM | Cost-optimised equivalent for volume issuance | Electrically interchangeable with DS1990A. Readers cannot tell the difference — it answers the same ROM commands. |
RW1990 / RW1990.2 | Yes — programmable with any TM duplicator | [object Object] | Blank for key-cutting shops and duplicating services | Emulates a DS1990A whose ID you can write and rewrite. The consumable behind every key-copying kiosk. |
TM08v2 | Yes — multi-format | [object Object] | Universal blank for mixed intercom estates | One blank covers Dallas plus the Cyfral and Metakom formats widely installed across the CIS — one SKU instead of three. |
TM-01A / RW2000 (OTP) | Once — programs a single time, then locks | [object Object] | Tamper-proof one-time copies for estates that ban rewritable blanks | After writing, an OTP blank behaves like a factory original — it can never be re-flashed, so a copy cannot become a master for further copies. |
Cyfral / Metakom | Format, not a part number | [object Object] | Legacy CIS intercom systems | Physically similar to a Dallas key but electrically different. A plain DS1990A will not open a Cyfral door. |
A genuine DS1990A-F5+ lists at roughly US $5 per piece in single quantities at Western catalogue distributors (DigiKey, 2026). That gap — not any quality defect — is why volume projects standardise on TM1990A-class equivalents and keep genuine parts for design validation.
Analog Devices completed its acquisition of Maxim Integrated in August 2021, and the iButton line remains in production under ADI — DS1990A is still listed as “Recommended for New Designs”. The original is not discontinued; its supply has simply consolidated, which is exactly why compatible equivalents carry the volume demand.
RW1990 covers the Dallas branch only. Cyfral (DC2000A-type) and Metakom keys use different silicon, and newer Vizit panels (roughly 2014 onward) moved to protected RFID keys entirely. A shop serving a mixed estate needs universal TM blanks plus 125 kHz RFID blanks — not more RW1990.
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