AT88SC0104C_03 데이터 시트보기 (PDF) - Atmel Corporation
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AT88SC0104C_03 Datasheet PDF : 9 Pages
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AT88SC0104CRF
Data is written first to a buffer zone in EEPROM instead of to the intended destination
address, but with the same access conditions. The data is then written to the required
location. If this second write cycle is interrupted due to a power loss, the device will
automatically recover the data from the system buffer zone at the next power-up.
Write Lock
If a user zone is configured in the write lock mode, then the user zone is effectively
divided into 8-byte pages. The lowest address byte of each 8-byte page constitutes a
write access control byte for the 8 bytes in that page.
Table 3. Example of the Write Lock Byte at $80 Controlling the Bytes from $80 to $87
$0
$1
$2
$3
$4
$5
$6
1101 1001 b xxxx xxxx b xxxx xxxx b xxxx xxxx b xxxx xxxx b xxxx xxxx b xxxx xxxx b
locked
locked
locked
$7
xxxx xxxx b
Page
$80
The write lock byte may also be locked by writing its least significant (rightmost) bit to
0b. Moreover, the write lock byte can only be programmed, i.e., bits written to 0b cannot
return to 1b.
In the write lock configuration, only one byte can be written at a time. If several bytes are
received by the PICC, the command will be NACKed.
Password Verification
Passwords may be used to protect user zones’ read and/or write access. When a
password is presented using the Check Password command, it is memorized and active
until power is removed unless a new password is presented or a valid DESELECT or
IDLE command is received. Only one password is active at a time, but write passwords
also give read access.
Authentication Protocol
The access to a user zone may be protected by an authentication protocol in addition to
password dependent rights.
The authentication success is memorized and active as long as the chip is powered,
unless a new authentication is initialized or a valid DESELECT or IDLE command is
received. If the new authentication request is not validated, the card loses its previous
authentication and it must be presented again. Only the last request is memorized.
Note: Authentication must be performed prior to the password check to insure password
security. If the trial’s limit has been reached (after four consecutive incorrect attempts),
the password verification or authentication process will fail.
Encryption
The data exchanged between the card and the reader during Read, Write, and Check
Password commands may be encrypted to ensure data confidentiality.
The issuer may choose to protect the access to a user zone with an encryption key by
settings made in the configuration zone. In that case, activation of the encryption mode
is required in order to read/write data in the zone.
The encryption activation success is memorized and active as long as the chip is
powered, unless a new initialization is initiated or a valid DESELECT or IDLE command
is received. If the new encryption activation request is not validated, the card will no
longer encrypt data during read operations nor will it decrypt data received during write
or verify operations.
7
5021AS–CRRF–05/03
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