8.3.5.4 Executing an Authentication Query

To execute an authentication query in UNSEALED mode, a host must first write 0x01 to the BlockDataControl() command to enable the authentication data commands. If in SEALED mode, 0x00 must be written to DataFlashBlock() instead.

Next, the host writes a 20-byte authentication challenge to the Authenticate() address locations (0x40 through 0x53). After a valid checksum for the challenge is written to AuthenticateChecksum(), the bq27546-G1 uses the challenge to perform the SHA-1/HMAC computation in conjunction with the programmed key. The bq27546-G1 completes the SHA-1/HMAC computation and writes the resulting digest to Authenticate(), overwriting the pre-existing challenge. The host should wait at least 45 ms to read the resulting digest. The host may then read this response and compare it against the result created by its own parallel computation.