SRIX4K, 13.56 MHz short-range contactless memory chip with 4096-bit EEPROM, anticollision and anti-clone functions

■ ISO 14443-2 Type B air interface compliant
■ ISO 14443-3 Type B frame format compliant
■ 13.56 MHz carrier frequency
■ 847 kHz subcarrier frequency
■ 106 Kbit/second data transfer
■ France Telecom proprietary anti-clone function
■ 8 bit Chip_ID based anticollision system
■ 2 count-down binary counters with automated antitearing protection
■ 64-bit unique identifier
■ 4096-bit EEPROM with write protect feature
■ Read_block and Write_block (32 bits)
■ Internal tuning capacitor
■ 1million erase/write cycles
■ 40-year data retention
■ Self-timed programming cycle
■ 5 ms typical programming time

The SRIX4K is a contactless memory, powered by an externally transmitted radio wave. It contains a 4096-bit user EEPROM fabricated with STMicroelectronics CMOS technology. The memory is organized as 128 blocks of 32 bits. The SRIX4K is accessed via the 13.56 MHz carrier. Incoming data are demodulated and decoded from the received amplitude shift keying (ASK) modulation signal and outgoing data are generated by load variation using bit phase shift keying (BPSK) coding of a 847 kHz subcarrier. The received ASK wave is 10% modulated. The data transfer rate between the SRIX4K and the reader is 106 Kbit/s in both reception and emission modes. The SRIX4K follows the ISO 14443-2 Type B recommendation for the radio-frequency power and signal interface.

The SRIX4K is specifically designed for short range applications that need secure and reusable products. The SRIX4K includes an anticollision mechanism that allows it to detect and select tags present at the same time within range of the reader. The anticollision is based on a probabilistic scanning method using slot markers. The SRIX4K provides an anticlone function which allows its authentication. Using the STMicroelectronics single chip coupler, CRX14, it is easy to design a reader with the authentication capability and to build a system with a high level of security.

The SRIX4K contactless EEPROM can be randomly read and written in block mode (each block containing 32 bits). The instruction set includes the following ten commands:
● Read_block
● Write_block
● Initiate
● Pcall16
● Slot_marker
● Select
● Completion
● Reset_to_inventory
● Authenticate
● Get_UID
The SRIX4K memory is organized in three areas, as described in Figure 12. The first area is a resettable OTP (one time programmable) area in which bits can only be switched from 1 to 0. Using a special command, it is possible to erase all bits of this area to 1. The second area provides two 32-bit binary counters which can only be decremented from FFFF FFFFh to 0000 0000h, and gives a capacity of 4,294,967,296 units per counter. The last area is the EEPROM memory. It is accessible by block of 32 bits and includes an auto-erase cycle during each Write_block command.