Roxtron — RFID & NFC datasheet library

Chip Memory Map Visualizer

Where UID, lock bytes, capability container, user memory and configuration pages live on each chip — drawn to scale from the datasheet.

NXP NTAG213 (180 B / 45 × 4-byte pages)

Layout: 45 pages × 4 bytes · Total: 180 B · Source: NTAG213/215/216 datasheet §8.5, Table 6
144 B
16 B
UID / manufacturer
Lock bytes
Capability Container
User memory
Configuration
UID / manufacturer databytes 0-7 · 8 B
Pages 0-1 (read-only)
Static lock bytesbytes 8-11 · 4 B
Page 2 (lock bits + internal)
Capability Container (CC)bytes 12-15 · 4 B
Page 3
User memorybytes 16-159 · 144 B
Pages 4-39 (144 B, NDEF)
Dynamic lock bytesbytes 160-163 · 4 B
Page 40
Configuration pagesbytes 164-179 · 16 B
Pages 41-44 (CFG0/1, PWD, PACK)

Why memory maps matter

Every RFID chip's user memory shares its silicon with a handful of housekeeping regions the datasheet spells out but readers glide past: the UID (factory-programmed and read-only), lock bytes that freeze pages once set, an OTP or Capability Container that tells NFC phones what's on the tag, and configuration pages that hold passwords, access rules, and mirror settings. This visualiser draws each of those regions to scale from the public datasheet — pages for the NTAG/Ultralight family, blocks and sector trailers for MIFARE Classic, 32-bit blocks for T5577, and 4-byte blocks for ICODE SLIX. Colour tells you the role at a glance: grey for factory UID, red for lock bytes, blue for user memory you can actually write NDEF to, orange for configuration. Hover any region to see the exact byte offset, the number of bytes, and the datasheet reference. The idea is to make it obvious why an NTAG216 has "888 bytes of user memory" but a 924-byte total — and why sector trailers on MIFARE Classic quietly eat 6% of your storage if you're planning to use every sector.

FAQ

Are these layouts exact to the datasheet?

Yes — each map cites the datasheet section it's drawn from. Where a chip has multiple variants (e.g. NTAG213/215/216 share a datasheet), each is drawn separately.

Why don't you cover MIFARE DESFire or NTAG 424 DNA here?

Those are file-based, not page-based — the addressable unit is an application + file, not fixed pages. A page-grid visual would misrepresent them; use the datasheet's file structure diagram instead.

What are lock bytes and sector trailers?

Lock bytes flip an individual page or range from writable to read-only (permanent on most chips). Sector trailers on MIFARE Classic hold two 6-byte keys and 4 access-condition bytes — one trailer per sector, non-negotiable.

Can I write to configuration pages?

Yes, but carefully. They control password protection, mirror behaviour, and access permissions; a bad write can permanently lock a tag.