The ICODE SLI-S is an NFC chip from NXP Semiconductors, the second member of the ICODE family, designed for applications requiring more memory and security: supply chain, asset management, container and pallet identification. Compliant with the ISO/IEC 15693 standard (known as vicinity) and compatible with the NFC Forum Type 5 format, it offers 160 bytes of user memory that can be protected by passwords. It can be read and written by the vast majority of recent NFC smartphones.
Information
| Manufacturer | NXP Semiconductors |
| Family | ICODE (SLI generation) |
| References | SL2 ICS53 and SL2 ICS54 (HC version) |
| 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) | 256 bytes (2,048 bits) |
| User memory | 160 bytes |
Memory
The EEPROM memory of the ICODE SLI-S is organized into 64 blocks of 4 bytes, grouped into pages of 4 blocks (16 bytes) for password protection; only the 40 user blocks can be addressed with the read and write commands:
| Area | Content | Access |
|---|---|---|
| Configuration area (24 blocks) | 64-bit UID, EPC memory (OTP), passwords, locks, AFI and DSFID | No direct access; managed through dedicated commands |
| Blocks 0 to 39 (pages 0 to 9) | User memory (160 bytes) | Read / write, lockable block by block, protectable page by page |
In practice, the 160 bytes of user memory can hold an NDEF record containing a URL of around 145 characters, once the Capability Container (written into the first block during formatting) and the NDEF envelope are taken into account, with the common prefix (https://www. for example) compressed into a single byte. Password protection applies per 16-byte page, allowing public and restricted areas to coexist on the same chip.
Features & security
- Five 32-bit passwords: five independent passwords (read, write, privacy, destroy and EAS) individually lockable, control the sensitive functions of the chip; the read and write passwords can be combined into a 64-bit protection.
- Page-level protection: each 16-byte page can be public, write-protected or read and write protected, a granularity that allows areas with differentiated access.
- Privacy mode: the Enable Privacy command silences the chip (it only responds to the Get Random Number and Set Password commands) until the privacy password is presented, in order to protect the holder's privacy.
- Destroy command: password protected, it disables the chip permanently and irreversibly; it will never respond to any command again.
- Selective EAS: the EAS anti-theft feature, protectable by password, manages an EAS identifier that triggers the alarm only for a given application.
- EPC memory: a 96-bit OTP area holds an EPC code that can be programmed only once, with a dedicated EPC command set and a long-range command.
- Locking and inventory: irreversible block-by-block locking (AFI, DSFID and EAS can also be locked) and multi-tag inventory with page reading during anticollision.
Unlike cryptographic authentication, the security of the ICODE SLI-S relies on passwords. The chip comes in two antenna tuning versions, SL2 ICS53 (23.5 pF) and SL2 ICS54 known as HC (97 pF) for small labels, and its backward-compatible successor is the ICODE SLIX-S.
Compatibility
The ICODE SLI-S 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-S chip supports reading technical information, writing records, erasing and permanent locking. Configuring the passwords and page protections is done through the chip's dedicated commands. The list of compatible models is available in the article on compatibility.
ICODE SLI vs ICODE SLI-S
| Chip | User memory | Security | Typical use |
|---|---|---|---|
| ICODE SLI | 112 bytes | EAS and AFI, block locking | Libraries, general logistics |
| ICODE SLI-S | 160 bytes | Five passwords, privacy, destroy, EPC memory | Secured supply chain, anti-counterfeiting |
Both chips share the ISO/IEC 15693 protocol and the same smartphone compatibility. The SLI-S adds extended memory and the full password protection arsenal; the range also includes the ICODE SLI-L, a reduced-memory version, and continues with the ICODE SLIX-S and then SLIX2, which take over and extend these features.
Frequently asked questions
How much data can be stored on an ICODE SLI-S?
The chip has 160 bytes of user memory, which corresponds to a URL of around 145 characters once the Capability Container and the NDEF envelope are taken into account. Password protection can be applied page by page, in 16-byte blocks.
What is the privacy mode for?
Once enabled, it silences the chip: it no longer responds to any command, except the random number request and the presentation of the privacy password. This mode protects the holder's privacy, for example after a labeled item has gone through checkout.
Is the ICODE SLI-S 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-S be protected against rewriting?
Yes, in two ways: a permanent, irreversible block-by-block lock, including from NFC Tools, or write protection by password, applied page by page and reversible by the password holder.
Useful links
