The ICODE SLI-L is the reduced-memory version of the first ICODE generation from NXP Semiconductors, designed for high-volume object identification with a particular focus on privacy: factory automation, industrial and laundry, asset management, libraries and rental. Compliant with the ISO/IEC 15693 standard (known as vicinity) and compatible with the NFC Forum Type 5 format, it offers 32 bytes of user memory along with privacy and destroy modes. Now replaced by the ICODE SLIX-L, it can still be read and written by the vast majority of recent NFC smartphones.
Information
| Manufacturer | NXP Semiconductors |
| Family | ICODE (first generation) |
| References | SL2 ICS50 and SL2 ICS51 |
| Standard | ISO/IEC 15693 (vicinity cards) |
| NFC Forum type | Type 5 Tag compatible |
| Operating frequency | 13.56 MHz |
| Data rate | Up to 53 kbit/s |
| Unique identifier (UID) | 8 bytes (64 bits), factory programmed |
| Operating distance | Up to 1.5 m with a long-range reader; a few centimeters with a smartphone |
| Data retention | 10 years |
| Write endurance | 100,000 cycles |
| Total memory (EEPROM) | 64 bytes (512 bits) |
| User memory | 32 bytes |
Memory
The EEPROM memory of the ICODE SLI-L is organized into 16 blocks of 4 bytes; only the 8 user blocks can be addressed with the read and write commands:
| Area | Content | Access |
|---|---|---|
| Configuration area | 64-bit UID, passwords, locks, AFI, EAS and DSFID | No direct access; managed through dedicated commands |
| Blocks 0 to 7 | User memory (32 bytes) | Read / write, lockable block by block |
In practice, the 32 bytes of user memory only leave room for a minimal NDEF record: a URL of around 20 characters once the Capability Container (written into the first block during formatting) and the NDEF envelope are taken into account. The chip is primarily designed for identification through its UID, with most of the information residing on the system side; for a consumer NFC tag intended to hold a link, an NTAG213 remains the appropriate choice.
Features & security
- Privacy mode: the Enable Privacy command silences the chip (it only responds to the Get Random Number and Set Password commands) until the 32-bit privacy password is presented, in order to protect the holder's privacy.
- Destroy command: protected by a 32-bit password, it disables the chip permanently and irreversibly; it will never respond to any command again.
- Password-protected EAS: the EAS anti-theft feature (with its identifier for selective alarm) can be placed under the protection of a 32-bit password: enabling, disabling and locking it then require its presentation. The AFI, however, cannot be password protected on this generation.
- Locking and inventory: irreversible block-by-block locking (AFI, DSFID and EAS can also be locked), multi-tag inventory with page reading during anticollision, and passwords that can themselves be locked.
- Long range and symmetrical range: a dedicated long-range command takes advantage of the European regulatory limits, and the write distance is equal to the read distance, an asset for encoding tags on the fly on a logistics line.
The ICODE SLI-L is limited to three passwords (privacy, destroy and EAS) and does not offer memory read and write passwords. The chip comes in two antenna tuning versions, SL2 ICS50 (23.5 pF) and SL2 ICS51 (97 pF) for small labels, and its replacement, the ICODE SLIX-L, extends password protection to the AFI.
Compatibility
The ICODE SLI-L uses NFC-V technology (ISO/IEC 15693), supported by the vast majority of recent NFC smartphones. On Android, reading and writing work natively with NFC Tools, without any particular restriction. On iPhone, automatic background reading is available from the iPhone XS and XR onwards; models from the iPhone 7 can read and write the chip via NFC Tools on iOS 15.6 or later, by starting the scan manually from the app.
With NFC Tools, the ICODE SLI-L chip supports reading technical information, writing records, erasing and permanent locking. The passwords are managed through the chip's dedicated commands. The list of compatible models is available in the article on compatibility.
ICODE SLI-L vs ICODE SLIX-L
| Chip | User memory | Security | Typical use |
|---|---|---|---|
| ICODE SLI-L | 32 bytes | Privacy, destroy, protected EAS | First generation, existing systems |
| ICODE SLIX-L | 32 bytes | Privacy, destroy, protected EAS and AFI | The replacement in the SLIX generation |
Both chips share the same memory, the same command set and the same trio of passwords. The SLIX-L extends password protection to the AFI and raises data retention to 50 years, compared with 10 years: it is the choice for any new deployment. For more memory, the ICODE SLIX and SLIX2 take over.
Frequently asked questions
How much data can be stored on an ICODE SLI-L?
The chip has 32 bytes of user memory, which corresponds to a URL of only around 20 characters once the Capability Container and the NDEF envelope are taken into account. It is primarily designed for identification through its UID rather than for storing content.
What is the difference between ICODE SLI-L and ICODE SLIX-L?
The memory, the commands and the three passwords are identical. The SLIX-L adds password protection for the AFI and raises data retention to 50 years, compared with 10 years for the SLI-L.
Is the ICODE SLI-L compatible with iPhones?
Yes. Background reading works from the iPhone XS and XR onwards, and both reading and writing are possible via NFC Tools from the iPhone 7 on iOS 15.6 or later.
Can an ICODE SLI-L be protected against rewriting?
A permanent, irreversible lock is possible block by block, including from NFC Tools. The chip does not offer a memory write password: for that feature, the ICODE SLI-S or SLIX-S are the chips to consider.
Useful links
