at88sc0104ca ATMEL Corporation, at88sc0104ca Datasheet - Page 13

• Manufacturer Part Number: at88sc0104ca
• Description: Cryptomemory
• Manufacturer: ATMEL Corporation

13.2
Figure 13-1. Write Lock Example
13.3
13.4
5200BS–CRYPT–2/09
Address
$080
Write Lock
Password Verification
Authentication Protocol
11011001
$0
If a user zone is configured in the write lock mode, the lowest address byte of an 8-byte page
constitutes a write access byte for the bytes of that page. For example, the write lock byte at
$080 controls the bytes from $081 to $087.
The Write-Lock byte itself may be locked by writing its least significant (rightmost) bit to “0”.
Moreover, when write lock mode is activated, the write lock byte can only be programmed – that
is, bits written to “0” cannot return to “1”.
In the write lock configuration, write operations are limited to writing only one byte at a time.
Attempts to write more than one byte will result in writing of just the first byte into the device.
Passwords may be used to protect READ and/or WRITE access of any user zone. When a valid
password is presented, it is memorized and active until power is turned off, unless a new pass-
word is presented or RST becomes active. There are eight password sets that may be used to
protect any user zone. Only one password is active at a time.
Presenting the correct WRITE password also grants READ access privileges.
The access to a user zone may be protected by an authentication protocol. Any one of four keys
may be selected to use with a user zone.
Authentication success is memorized and active as long as the chip is powered, unless a new
authentication is initialized or RST becomes active. If the new authentication request is not vali-
dated, the card loses its previous authentication which must be presented again to gain access.
Only the latest request is memorized.
xxxx xxxx
locked
$1
xxxx xxxx
locked
$2
xxxx xxxx
$3
xxxx xxxx
$4
xxxx xxxx
locked
$5
xxxx xxxx
$6
xxxx xxxx
$7
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