AT88SC153 View Datasheet(PDF) - Atmel Corporation
Part Name
Description
MFG CO.
'AT88SC153' PDF : 24 Pages View PDF
Initialize Authentication
Figure 10. Initiatize Authentication
AT88SC153
Verify Authentication
Note: Q: Host random number, 8 bytes
The Initialize Authentication command sets up the random generator with the crypto-
gram (Ci), the secret seed (Gc), and the host random number (Q). Once the sequence is
completed and a stop condition is issued, there is a nonvolatile write cycle to clear a
new bit of the AAC. In order to complete the authentication protocol, the device requires
the host to perform an ACK polling sequence with the specific command byte of $B6,
corresponding to the Verify Authentication command.
Figure 11. Verify Authentication
Q1(0)
1
Q1(1)
Q1(7)
Device Operation
Clock and Data
Transitions
Start Condition
Note: Q1: Host challenge, 8 bytes
If Q1 is equal to Ci + 1, then the device writes Ci + 2 in memory in place of Ci; this must
be preceded by the Initialize Authentication command. Once the sequence is completed
and a stop condition is issued, there is a nonvolatile write cycle to update the associated
attempts counter. In order to know whether or not the authentication was correct, the
device requires the host to perform an ACK polling sequence with the specific command
byte of $BD, to read the corresponding attempts counter in the configuration zone. A
valid authentication will result in the AAC cleared to $FF. An invalid authentication
attempt will initiate a nonvolatile write cycle, but no clear operation will be performed on
the AAC.
The SDA pin is normally pulled high with an external device. Data on the SDA pin may
change only during SCL-low time periods (Figure 13 on page 14). Data changes during
SCL-high time periods will indicate a start or stop condition as defined below.
A high-to-low transition of SDA with SCL high is a start condition that must precede any
other command (Figure 12 on page 14).
13
1016D–SMEM–04/04
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