LF Legacy 
HITAG S
For animal identification, laundry and industrial LF applications.
Security 48-bit key
Memory 32 / 256 B
EM4100 / EM4200: Technical Data, Security and Use
EM4100 and EM4200 from EM Microelectronic are contactless LF RFID chips for simple identification applications. The EM4200, which EM Microelectronic currently lists, operates in the frequency range of 100 to 150 kHz and is designed as a direct replacement for EM4100/4102 and EM4005/4105. The identification data is written at the factory into a laser-programmed read-only memory and continuously transmitted by the transponder.
We offer EM4100 / EM4200 mainly as a legacy solution for older 125 kHz access control systems and key fobs. The chip has no cryptographic authentication or encryption. It may therefore still be required for existing systems. For new access control systems with security requirements, on the other hand, a chip family with cryptographic authentication should be considered.
| Feature | Value |
|---|---|
| Manufacturer | EM Microelectronic |
| Product family | LF Animal & Access ICs |
| Type designation | EM4100 / EM4102 (legacy), EM4200 |
| RFID class | LF |
| Frequency | 100–150 kHz for the EM4200; typical EM4100 systems 125 kHz |
| Standard / protocol | Proprietary LF protocol; EM4200 compatible with EM4100/4102 and EM4005/4105 |
| Data rate / encoding | Manchester 32/64 RF, Biphase 32/64 RF, PSK 16 RF or FSK2 50 RF, depending on the variant |
| ROM / total memory | 128-bit laser-programmed ROM for the EM4200; 64- and 96-bit options available |
| User Memory | No freely writable user memory |
| Memory structure | Factory laser-programmed read-only code |
| Authentication | No cryptographic authentication |
| Encryption | None |
| Identifier | Factory-programmed read-only code; 64, 96 or 128 bits depending on the EM4200 variant |
| Anti-collision | No anti-collision function specified in the EM4200 data sheet |
| Read range | Depends on reader, antenna, transponder coil and resonance tuning; no general distance specified by the manufacturer |
| Write cycles | Not relevant, read-only ROM |
| Data retention | No corresponding lifetime specification stated in the relevant EM4200 data sheet |
| Smartphone NFC | Not directly supported |
| Product status at manufacturer | EM4200 currently listed; several variants “Available on demand” |
| Typical media | RFID card, key fob and LF special transponders |
| Security rating | None |
| Recommendation | Mainly for existing LF systems |
The EM4200 is a pure read-only transponder. EM Microelectronic specifies 128 bits of laser-programmed ROM and offers mask options with 64, 96 or 128 output bits. For the typical EM4100-compatible variant, 64 bits with Manchester encoding are available, among others. Unlike writable RFID chips, there is no freely usable user memory.
The EM4200 supports several encoding and data rate options, including Manchester, Biphase, PSK and FSK. The manufacturer specifies an operating frequency range of 100 to 150 kHz; typical EM4100-compatible access control systems operate at 125 kHz.
Typical Applications
For the EM4200 chip, EM Microelectronic names in particular applications in which a permanently programmed identifier is sufficient for identification. These include:
- access control,
- animal identification according to ISO 11785 FDX-B with appropriately configured variants,
- waste management,
- logistics automation,
- industrial transponders and
- simple identification applications.
In practice, EM4100 / EM4200 is used today mainly in older 125 kHz access control systems and key fobs. In such existing installations, the fixed identifier typically serves as a reference to a data record in the backend system.
Particularly suitable media are RFID cards, RFID key fobs and application-specific LF special transponders. When reordering, it should be checked in advance which data format and encoding the existing reader actually expects.
Security
Security level: No cryptographic security
EM4100 / EM4200 is not designed as a cryptographic security chip. The EM4200 transmits the factory-programmed identifier from its read-only ROM. The data sheet describes neither mutual authentication nor encryption or key management.
Although the read-only design prevents the identifier stored in the original chip from being rewritten later, it does not cryptographically authenticate the transponder to the reader. A received identifier is therefore not automatically proof that the original transponder is present.
For existing installations in which the system explicitly expects EM4100/EM4200-compatible media, this technology may still be required.
For new access control or ID card systems that require protection against copying or emulating identification data, a chip technology with cryptographic authentication should be used.
Advantages and Disadvantages of EM4100 / EM4200
| Advantages | Disadvantages |
|---|---|
| EM4200 supports the communication protocols of older EM4100/4102 systems | No cryptographic authentication or encryption |
| Fixed read-only identifier cannot be overwritten later in the original chip | No freely writable user data |
| Several encoding and data rate options available for the EM4200 | Normal smartphone NFC cannot read 125 kHz LF transponders directly |
| Still relevant for existing 125 kHz reader infrastructures | A fixed identifier alone offers no cryptographic protection against cloning |
| Can be used as card, key fob and special transponders | Reader compatibility also depends on encoding and data format |
Alternatives to EM4100 / EM4200
Depending on the existing reader infrastructure, security requirements and desired frequency, other chip types may be better suited.
HF Legacy 
MIFARE Classic 1K
For existing access control and hotel systems in the HF range. Only partially readable by smartphone.
Security Broken
Memory 1 KB
HF / NFC Recommendation 
MIFARE DESFire EV3
For secure company ID cards and multi-application cards.
Security AES-128
Memory 2 / 4 / 8 / 16 KB
Frequently Asked Questions about EM4100 / EM4200
How much memory does EM4100 / EM4200 have?
The EM4200 is not a classic RFID memory chip with freely writable user memory. The chip has 128 bits of laser-programmed ROM; depending on the mask option, 64, 96 or 128 bits can be used or transmitted. A standard variant, for example, works with 64 bits and Manchester encoding. The data is programmed during manufacturing and cannot subsequently be changed as with an EEPROM-based RFID chip. The frequently cited “64-bit UID” therefore describes a common EM4100-compatible version, not the entire memory configuration of all EM4200 variants.
What is the difference between EM4100 and EM4200?
EM Microelectronic explicitly developed the EM4200 as a direct replacement for the older read-only ICs EM4100/4102 and EM4005/4105. The manufacturer states that it is fully compatible with the communication protocols of these older chips. Compared to the EM4100/4102, the EM4200, according to the manufacturer, offers improved read range performance and various integrated resonance capacitor options, among other things. The manufacturer's current website lists the EM4200, while EM4100 is mainly relevant as the designation of older or existing systems.
Can EM4100 / EM4200 be written?
No. The EM4200 is designed as a read-only identification chip. Its identifier is stored in a laser-programmed ROM and is fixed during manufacturing. The data sheet describes no writable user memory and no function with which a user could subsequently change the stored identifier. For applications in which data in the transponder must be updated, a read/write chip is therefore required. EM Microelectronic, for example, offers separate LF products with writable memory in the EM4205/EM4305.
How secure is EM4100 / EM4200?
EM4100 / EM4200 has no cryptographic authentication and no encryption. The transponder sends its permanently programmed identifier as soon as it receives sufficient energy from the reader's electromagnetic field. The read-only memory merely protects against the identifier being rewritten in the original chip. It does not cryptographically prove the authenticity of the transponder. This principle may be sufficient for simple identification or existing installations. For new security-critical access control systems, a technology with cryptographic authentication should be considered.
Which readers support EM4100 / EM4200?
A reader must support the LF protocol, encoding and data format of the specific transponder. According to the manufacturer, the EM4200 operates between 100 and 150 kHz and is compatible with the communication protocols of EM4100/4102 and EM4005/4105. Different encodings such as Manchester, Biphase, PSK and FSK as well as different data rates are available. The specification “125 kHz” alone therefore does not guarantee compatibility in every case. For reorders, the reader model and existing transponder should be checked.
Can EM4100 / EM4200 be read with a smartphone?
Not directly with a smartphone's normal NFC module. EM4100 / EM4200 belongs to the LF range and is typically used at 125 kHz. Smartphone NFC, on the other hand, operates in the HF range at 13.56 MHz. For a smartphone application, an external LF reader or a different chip technology is required. For classic NFC applications with URLs or NDEF content, HF/NFC chips designed for this purpose are suitable, for example.
What is the read range of EM4100 / EM4200?
EM Microelectronic does not state a general centimeter value for the EM4200 that applies regardless of the transponder construction. Compared to the EM4100/4102, the manufacturer describes improved read range performance. However, the actual distance depends on the reader, reader antenna, transponder coil, resonance tuning and environment. LF systems generally operate at close range of a few centimeters. A specific read range should therefore be tested for the planned medium and the existing reader instead of assuming a fixed value for all EM4200 transponders.
When does EM4100 / EM4200 still make sense today?
The chip is mainly relevant for existing 125 kHz systems whose readers and backend are designed for EM4100-compatible identification media. Typical cases are replacement cards or additional key fobs for existing access control installations. For a new system, it should be checked whether the mere transmission of a fixed identifier is actually sufficient. If protection against copying or emulation is required, a chip technology with cryptographic authentication is the more suitable technical basis.
Is EM4200 still being produced?
EM Microelectronic still lists the EM4200 on its current product website and lists several order variants as “Available on demand”. The manufacturer continues to describe it as a read-only LF identification chip and a direct replacement for EM4100/4102 and EM4005/4105. For a specific procurement, availability, package type, encoding, data length and resonance capacitor option should be checked, as the EM4200 is offered in different mask variants.
Request RFID Media with EM4100 / EM4200
Do you need RFID cards or key fobs for an existing EM4100/EM4200 system?
For the review, the desired media format, quantity and the manufacturer and model of the existing reader are particularly helpful. If possible, an existing transponder or information on encoding and data format should also be available. This makes it possible to check which EM4100-compatible variant is required.
Technical sources
Data as of: September 2026
The technical information is based on the data sheet EM4200 – 128 bit Read Only Low Frequency Contactless Identification Device, Version 3.2 dated 8 November 2013, the EM4200 Fact Sheet, Version 3.0 dated 7 October 2014, and the current product page of EM Microelectronic. Among other things, the data sheet documents the frequency range of 100 to 150 kHz, the 128-bit ROM with 64- and 96-bit options, the available encoding methods and compatibility with EM4100/4102 and EM4005/4105.
Trademark notice
EM4100 and EM4200 are product names of EM Microelectronic.