AT88SC0104CA_11 ATMEL [ATMEL Corporation], AT88SC0104CA_11 Datasheet - Page 21

• Manufacturer Part Number: AT88SC0104CA_11
• Description: Atmel CryptoMemory Specification Datasheet
• Manufacturer: ATMEL [ATMEL Corporation]

6.3.9.4 WLM – Write Lock Mode
6.3.9.5 MDF – Modify Forbidden
6.3.9.6 PGO – Program Only
6.3.10 Password/Key Registers
6.3.10.1 AK(1:0) – Authentication Key
6.3.10.2 POK(1:0) – Program Only Key
6.3.10.3 PW(2:0) – Password Set
6.3.11 Identification Number
6.3.12 Cryptograms (C
Asserting this bit (WLM = “0”) divides the user zone into 8-byte pages. The first byte of each page becomes the write lock byte
and defines the locked/unlocked status for each byte in the page. Write access is forbidden to a byte if its associated bit in the
write lock byte is set to “0”. Bit 7 controls byte 7; bit 6 controls byte 6, etc. By setting bit 0 to “0” locks the write lock byte itself.
Enabling write lock mode limits write operations to one byte at a time.
Asserting this bit (MDF = “0”) renders the user zone read-only at all times. The user zone must, therefore, be programmed
before setting this bit to “0”
Asserting this bit (PGO = “0”) allows changing of data within the user zone under protection from “1” to “0” and never from “0”
to “1”.
Four (AT88SC0104CA/0204CA/0404CA) or eight (AT88SC0808CA) 8-bit password/key registers receive definition during
device personalization. Each password/key register works in conjunction with a corresponding access register to define the
security settings of each zone. The values programmed have an immediate effect on the logic of the device. The default value
is “1” for each bit. Bit 3 is reserved and should be left as value “1.”
Table 6-8.
These bits define which of the four secret seeds G
authentication is selected in the corresponding access register. Each access register may point to a unique authentication
secret, or access registers for multiple zones may point to the same authentication secret. In this case authentication with a
single secret seed will open several zones.
When the user zone has the dual access mode selected (AM = "00"), these bits define which of the four secret seeds G
must be used in an authentication to allow read and program (i.e. write '0's only) access to the user zone.
These bits define which of the eight password sets must be presented to allow access to the user zone when the password
mode is selected.
A 56-bit number the customer defines during personalization. It is recommended that a unique identification number be
assigned to each device.
Each of these fields contains a 56-bit cryptogram for use during authentication. The internal logic modifies the cryptogram
each time it successfully verifies the authentication. The customer may program an initial value for the cryptogram during
personalization. It is recommended that the initial values be random numbers.
Bit 7
AK1
Password/Key Register Bit Map
0
– C
Bit 6
AK0
3
)
POK1
Bit 5
Atmel AT88SC0104CA/0204CA/0404CA/0808CA [Datasheet]
0
-G
POK0
Bit 4
3
must be used in an authentication to allow access to the user zone if
Bit 3
Res
Bit 2
PW2
Bit 1
PW1
8664E−CRYPTO−12/11
Bit 0
PW0
0
-G
3
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