LF 125 kHzNXP

HITAG 2

Name: NXP HITAG 2
Brand: NXP

The NXP HITAG 2 is an LF 125 kHz RFID tag IC, with 256 bits total (32 bytes) organized in 8 pages of 4 bytes each. 128 bits (16 bytes) user data in pages 4-7; 128 bits control/secret memory in pages 0-3. Serial Number: 32 bits. Secret Key: 48 bits. Password TAG: 24 bits. Password RWD: 32 bits., operating at 125 kHz, under Proprietary HITAG 2 protocol (not ISO/IEC 14443 or 15693). Emulation modes: Public Mode A (MIRO/µEM H400x compatible, Manchester), Public Mode B (ISO 11784/11785 animal ID, Biphase), Public Mode C (PIT compatible Biphase).

256-bit Crypto-1, vehicle immobilizers and access

Official Datasheet ↗

Frequency

125 kHz

Protocol

Proprietary HITAG 2 protocol (not ISO/IEC 14443 or 15693). Emulation modes: Public Mode A (MIRO/µEM H400x compatible, Manchester), Public Mode B (ISO 11784/11785 animal ID, Biphase), Public Mode C (PIT compatible, Biphase)

Memory

256 bits total (32 bytes) organized in 8 pages of 4 bytes each. 128 bits (16 bytes) user data in pages 4-7; 128 bits control/secret memory in pages 0-3. Serial Number: 32 bits. Secret Key: 48 bits. Password TAG: 24 bits. Password RWD: 32 bits.

Interface

RF contactless only (no battery, passive). Data transmission: half-duplex. Tag to reader: 4.0 kbit/s Manchester or Biphase coding. Reader to tag: 5.2 kbit/s BPLM (binary pulse length modulation). Modulation: ASK (amplitude shift keying). Absorption modulation from tag to reader.

Temp Range

-40°C to +85°C operating, -55°C to +125°C storage

Form Factor

HT2 DC20 S20/F: Stick transponder, 12 x 6 x 3 mm, epoxy resin encapsulated (black), IP67 rated

Full Specifications

Manufacturer	NXP
Frequency Category	LF 125 kHz
Frequency	125 kHz
Protocol	Proprietary HITAG 2 protocol (not ISO/IEC 14443 or 15693). Emulation modes: Public Mode A (MIRO/µEM H400x compatible, Manchester), Public Mode B (ISO 11784/11785 animal ID, Biphase), Public Mode C (PIT compatible, Biphase)
Memory	256 bits total (32 bytes) organized in 8 pages of 4 bytes each. 128 bits (16 bytes) user data in pages 4-7; 128 bits control/secret memory in pages 0-3. Serial Number: 32 bits. Secret Key: 48 bits. Password TAG: 24 bits. Password RWD: 32 bits.
Interface	RF contactless only (no battery, passive). Data transmission: half-duplex. Tag to reader: 4.0 kbit/s Manchester or Biphase coding. Reader to tag: 5.2 kbit/s BPLM (binary pulse length modulation). Modulation: ASK (amplitude shift keying). Absorption modulation from tag to reader.
Temperature Range	-40°C to +85°C operating, -55°C to +125°C storage
Form Factor	HT2 DC20 S20/F: Stick transponder, 12 x 6 x 3 mm, epoxy resin encapsulated (black), IP67 rated
Security	Mutual authentication with proprietary 48-bit crypto stream cipher. Password mode (32-bit Password RWD, 24-bit Password TAG). Crypto mode (48-bit secret key, encrypted data transmission). Selective read/write protection per page via configuration byte. One-time programmable (OTP) lock bits for pages 1, 2, 3 (Bit 6 and Bit 7 in configuration byte). User-defined write protection. Authentication duration: ~36 ms.

Engineering Brief

The HITAG 2 (HT2 DC20 S20) is a 125 kHz LF passive RFID transponder with 256 bits of EEPROM (128 bits user, 128 bits control/secret) organized in 8 pages. It supports mutual authentication using a proprietary 48-bit stream cipher in crypto mode or 32-bit password authentication in password mode, enabling secure bidirectional read/write communication. The chip offers flexible operation modes including crypto, password, and three public (read-only emulation) modes compatible with legacy systems (MIRO, ISO 11784/11785 animal ID, PIT). Key features include selective page write protection, OTP lock bits, multi-tag operation via HALT command, 10-year data retention, >100,000 write cycles, and operation from -40°C to +85°C, making it ideal for automotive immobilizers, secure access control, and industrial identification.

Typical Applications

Standards & Compliance

ISO 11784 / 11785 (Animal ID)

Frequently Asked Questions

How much user memory does the HITAG 2 have?

The HITAG 2 has 128 bits (16 bytes) of user data memory organized in pages 4-7. The total memory is 256 bits (32 bytes) with the remaining 128 bits used for control data, serial number, secret key, and passwords.

What security features does the HITAG 2 support?

HITAG 2 supports mutual authentication with a proprietary 48-bit stream cipher in crypto mode, or password authentication using a 32-bit reader password and 24-bit tag password. It also offers selective page write protection and one-time programmable lock bits for pages 1, 2, and 3.

What operating frequency does the HITAG 2 use?

HITAG 2 operates at 125 kHz in the low frequency (LF) RFID band. It uses a proprietary HITAG 2 protocol, not ISO 14443 or ISO 15693 standards.

Can HITAG 2 emulate other RFID tag formats?

Yes, HITAG 2 supports three public emulation modes: Public Mode A (MIRO/µEM H400x compatible with Manchester coding), Public Mode B (ISO 11784/11785 animal ID with Biphase coding), and Public Mode C (PIT compatible with Biphase coding). These are read-only modes for legacy system compatibility.

What is the data transmission speed of HITAG 2?

HITAG 2 transmits data from tag to reader at 4.0 kbit/s using Manchester or Biphase coding, and receives data from reader to tag at 5.2 kbit/s using BPLM (binary pulse length modulation) with ASK modulation.

How long does HITAG 2 authentication take?

The mutual authentication process in HITAG 2 takes approximately 36 milliseconds to complete when using crypto mode with the 48-bit secret key.

Explore

Manufacturer

All NXP chips →

Standards

ISO 11784 / 11785 (Animal ID)

Applications

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