AT88SC1608 データシートの表示（PDF） - Atmel Corporation

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AT88SC1608

8 x 256 x 8 Secure Memory with Authentication

Atmel Corporation 

AT88SC1608

Initialize Authentication

Figure 11. Initialize Authentication

S

T

A

R

T Command

Q0(0)

1 0 1 1 0 1 1 0 D7 –

A

C

K

D0 D15

A

C

K

Q0(1)

–

D8

. . . D63

A

C

K

Q0(7)

–

S

T

O

P

D56

A

C

K

Note: Q0: 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 (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.

Verify Authentication

Figure 12. Verify Authentication

S

T

A

R

T

Command

Q1(0)

Q1(1)

S

T

O

Q1(7)

P

Note:

1 0 1 1 0 1 1 0 D7

A

C

K

–

D0 D15

–

A

C

K

D8

D63

...

–

A

C

K

D56

A

C

K

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 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.

Device Operation

Clock and Data

Transitions

Start Condition

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).

13

0971G–SMEM–04/04

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