NFC Reader Column：ISO14443 Introduction

NFC Reader Column：ISO14443 is a 4-part protocol with distinct layers: ISO14443-1 (physical characteristics), ISO14443-2 (RF power and signal interface), ISO14443-3 (initialization and anti-collision), and ISO14443-4 (transport protocol). ISO14443A and ISO14443B share the same structure, with sections specific to each type.

PCD (Proximity Coupling Device): Reader/writer.
PICC (Proximity Card): Tag.
SAK (Select Acknowledge)
UID (Unique Identifier)

Commands:

REQA/WUPA: Used by the PCD to check for the presence of a card (7-bit command code). WUPA responds to cards in IDLE or HALT states, while REQA responds only to cards in IDLE. Cards enter HALT state after receiving a HALT command.

ANTICOLISION and SELECT: Used for anti-collision when multiple cards are detected.
- Format: SEL (Selection code: 0x93 (Level 1), 0x95 (Level 2), 0x97 (Level 3)), NVB (Number of Valid Bits: indicates the number of transmitted bytes and bits), UID (Unique ID, length varies based on collision, 0-40 bits indicated by NVB).
- Anti-collision iteratively polls UID bits to select a specific card.
HALT: Puts the card into a sleep state. No response is sent by the card. Includes a 2-byte CRC_A.
ATQA: Response to REQA or WUPA. Includes: Proprietary coding, UID size, and a collision bit (non-
zero indicates multiple cards).

SAK: Response to SELECT. Indicates UID completeness and ISO14443-4 support (bits 3 and 6).

PCD Detection Process:

PICC Detection: PCD sends REQA, PICC responds with ATQA (identifies ISO14443A).
Anti-collision: Resolves multiple card detection (3 levels based on UID length).
PICC Type Determination: PICC sends SAK, PCD parses to determine ISO14443-4 support.

Anti-Collision Flow:

PCD sets SEL and NVB, then sends ANTICOLLISION (e.g., NVB=0x20 means 2 bytes: SEL and NVB).
Bit collisions are checked. If collisions occur, PCD chooses 0 or 1 and re-sends ANTICOLLISION until no collisions remain.
Once no collisions exist, PCD sends SELECT, and the PICC responds with SAK.