at88sc1608 ATMEL Corporation, at88sc1608 Datasheet - Page 13

• Manufacturer Part Number: at88sc1608
• Description: 8 X 256 X 8 Secure Memory With Authentication
• Manufacturer: ATMEL Corporation

Initialize Authentication
Verify Authentication
Figure 12. Verify Authentication
Note:
Device Operation
Clock and Data
Transitions
Start Condition
0971G–SMEM–04/04
S
T
A
R
T
Q1: Host challenge, 8 bytes
1 0 1 1 0 1 1 0
Command
A
C
K
D 7
Figure 11. Initialize Authentication
Note:
The initialize authentication command sets up the random generator with the crypto-
gram (Ci), the secret seed (Gc), and the host random number (Q0). Once the sequence
is completed and a stop condition is issued, there is a nonvolatile write cycle to write a
new bit of the 8-bit AAC to “0”. In order to complete the authentication protocol, the
device requires the host to perform an ACK polling sequence with the specific device
address of $B7, corresponding to the verify authentication command.
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 device
address of $B5 to read the AAC in the configuration zone. A valid authentication will
result in the AAC cleared to $FF. An invalid authentication attempt will initiate a nonvol-
atile 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 (see Figure 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 which must precede
any other command (see Figure 13).
S
T
A
R
T
1 0 1 1 0 1 1 0
Command
Q1(0)
Q0: Host random number, 8 bytes
–
D 0
A
C
K
A
C
K
D
7
D 15
Q0(0)
–
Q1(1)
–
D
0
A
C
K
D
D 8
15
A
C
K
Q0(1)
–
. . .
D
D 63
8
A
C
K
. . .
AT88SC1608
Q1(7)
–
D
63
Q0(7)
D 56
–
A
C
K
D
S
T
O
P
56
A
C
K
S
T
O
P
13