8.7.1 Functional

The Write User Zone command ($B0) allows writing of data to the device's currently selected user zone (the procedure for selecting a user zone is described in section 8.10 System Write: $B4.

The data byte address to be written is defined by Address 1 and Address 2 in the command. The value N defines how many bytes are to be written. The maximum number of bytes that may be written is $10, corresponding to the EEPROM page size. In Anti-Tearing mode, the maximum value for N is $08 for all devices. A write in Anti-Tearing mode is activated with the set user zone with Anti-Rearing command; all subsequent write operations to the user zone will be in Anti-Tearing mode. A write may be started in the middle of an EEPROM page but must not extend past the end of the page.

When a Write User Zone command is sent in Authentication mode or Encryption mode, the data are saved in a buffer until a cryptographic checksum is received. The host must send the checksum it has computed immediately after the Write User Zone command. If the checksum is valid, CryptoMemory® writes the data; if the checksum is incorrect, the data are discarded and the cryptographic engine is reset. If the host is not allowed to write in the zone, the device will not acknowledge the N byte. After this command, the host must perform ACK polling.