SRI512, 13.56 MHz short-range contactless memory chip with 512-bit EEPROM and anticollision functions
The SRI512 is a contactless memory, powered by an externally transmitted radio wave. It contains a 512-bit user EEPROM fabricated with STMicroelectronics CMOS technology. The memory is organized as 16 blocks of 32 bits. The SRI512 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 SRI512 and the reader is 106 Kbit/s in both reception and emission modes. The SRI512 follows the ISO 14443-2 Type B recommendation for the radio-frequency power and signal interface.
The SRI512 is specifically designed for short range applications that need re-usable products. The SRI512 includes an anticollision mechanism that allows it to detect and select tags present at the same time within range of the reader. Using the STMicroelectronics single chip coupler, CRX14, it is easy to design a reader and build a contactless system.
The SRI512 contactless EEPROM can be randomly read and written in block mode (each block containing 32 bits). The instruction set includes the following nine commands:
● Read_block
● Write_block
● Initiate
● Pcall16
● Slot_marker
● Select
● Completion
● Reset_to_inventory
● Get_UID
The SRI512 memory is organized in three areas, as described in Table 3. 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 that 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.
