ISO/IEC 14443 Quick Reference
One-page reference for ISO/IEC 14443 contactless smart cards: parts, layers, Type A vs Type B, anti-collision, framing.
Parts of the standard
| Part | Topic | Notes |
|---|---|---|
| -1 | Physical characteristics | Card dimensions; environmental tolerances. |
| -2 | RF interface | 13.56 MHz, modulation, coding, signalling. Type A = ASK 100% / Miller; Type B = ASK 10% / NRZ. |
| -3 | Initialisation & anti-collision | REQA / WUPA, anti-collision loops, SELECT, UID handling. Cascade for 7- and 10-byte UIDs. |
| -4 | Transmission protocol | Block-oriented half-duplex protocol. RATS / ATS, I-blocks / R-blocks / S-blocks, framing. |
Anti-collision in five lines
- REQA / WUPA — reader probes the field for Type A cards.
- ATQA — cards in field reply with their Answer To reQuest A.
- Anti-collision loop — reader narrows in on each card by UID prefix until a single PICC is selected.
- SELECT — reader issues SELECT for a specific UID. PICC responds with SAK (Select Acknowledge) telling the reader what protocol it speaks (e.g. ISO 14443-4 compliant).
- RATS / ATS — reader requests the protocol parameters; PICC answers; reader caches.
I / R / S blocks (Part 4)
| Block | Use |
|---|---|
| I-block | Information block — carries application APDUs. Chained for long messages. |
| R-block | Receive-ready / negative-acknowledge — for chaining and error recovery. |
| S-block | Supervisory — wait-time extension (WTX) and deselect. |
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Where this fits
ISO/IEC 14443 is the contactless companion to ISO/IEC 7816. The application-layer APDUs that ride on top are the same on both sides — once the contactless link is established, you are talking 7816-4 over a 14443-4 transport. DESFire layers its proprietary command set on top of the same APDU envelope.