AT88SC0104C datasheet(48/58 Pages) ATMEL

48 / 58 page

5210B–SMIC–11/08

AT88SC0104/0204/0404/0808/1616/3216/6416/12816/25616C

8.5.4.3

Read Fuse Byte

Fuse data is returned in the form of a single byte. Bits 0 to 3 represent the fuse states; a value of

‘0’ indicates the fuse has been blown. Bits 4 to 7 are not used as Security Fuses and are

reserved by Atmel.

8.5.5

Verify Password: $BA

8.5.5.1

Functional

Figure 8-5.

Verify Password Command Functional Description

Read password indices : $10 to $17 for passwords 0 to 7.

Write password indices : $00 to $07 for passwords 0 to 7.

Secure code index : $07 (equivalent to Write 7 Password).

Four password index bits "r" and "ppp" indicate the password to compare :

r = 0: Write password,

r = 1: Read password,

p2p1p0: Password set number.

If the maximum number of trials has been exceeded, the device will return $69 $00 instead of

the INS code, after receiving the header, to indicate the command is unauthorized. The device

decrements the associated attempts counter before verifying the password, to prevent attacks. If

the password is correct, the device memorizes this success, clears the pasword attempts coun-

ter and returns $90 $00. If the password is wrong, the device simply returns $69 $00 after

decrementing the attempts count. The Write 7 password is also known as the Secure Code and

must be properly presented before access to the configuration memory is granted when person-

alizing the device

Table 8-13.

Fuse Byte Description

resv

SEC

PER

CMA

FAB

Device

Command

Password Index

PW1

PW2

PW3

Host

3 password bytes

Table 8-14.

Verify Password

Data Sent

CLA

INS :

Command

PW1

PW2

PW3

$BA

000r 0p2p1p0

$03

d7--- ---d0

d15--- ---d8

d23--- ---d16

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