7.5.1 Device Response to a Write Operation on a Locked Device

A locked device will respond differently to a write operation to the Security register compared to a device that has not been locked. Writing to the Security register is accomplished by sending a Start condition, followed by a device address byte with the opcode of 1011b (Bh), the appropriate client address combination, and the Read/Write bit set as a logic ‘0’. Both a locked device and a device that has not been locked will return an ACK. Next, the 8-bit word address is sent, and again, both devices will return an ACK. However, upon sending the data input byte, a device that has already been locked will return a NACK and will be immediately ready to accept a new command, whereas a device that has not been locked will return an ACK to the data input byte as per normal operation for a write operation as described in Write Operations.