AT88SC0104CA_11 ATMEL [ATMEL Corporation], AT88SC0104CA_11 Datasheet - Page 20

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

6.3.9.1 PM(1:0) Password Mode
6.3.9.2 AM(1:0) – Authentication mode
6.3.9.3 ER – Encryption Required
Table 6-6.
When PM = “11”, the user zone under protection requires no password. When PM = “10”, the zone requires write password
verification for writing and reading is free. When PM = “01” or “00”, reading requires the read password verification and writing
requires write password verification. However, proper verification of the write password also grants read access. The
password set required is specified by PW(3:0) in the corresponding passwords/keys register (see Section 6.3.10,
Password/Key
Table 6-7.
When AM = “11”, the user zone under protection requires no authentication. When AM = “10”, the zone requires authentication
only for write accesses and read accesses are free. When AM = “01”, the zone requires authentication for both write and read
accesses. In both of these configurations, the Authentication Key (AK) in the corresponding passwords/keys register specifies
the required secret seed and corresponding cryptogram, and when applicable the session encryption key (see the following
Section 6.3.10).
Finally, when AM = “00”, the dual access mode is active in which authentication using the Program Only Key (POK) gives a
right to read and program the zone (i.e. write '0's only), while authentication using the AK gives full read and write access to
the zone. In this way, a token application may be implemented, whereby regular hosts with knowledge of POK may decrement
the stored value, and only master hosts with knowledge of AK may reset the token to its full value. Please see the following
Section 6.3.10on the passwords/keys register for further definition of POK and AK.
Notes:
When ER = "0", the host is required to activate the encryption mode in order to read/write the corresponding user zone. No
data read from or written to the zone may be transmitted in the clear. If ER = "1", the host may activate the encryption mode,
but isn't specifically required to do so by the device.
PM0
AM1
1
1
0
1
1
0
0
1.
2. When AM = ‘00’ and PGO = ‘0’; bits in the zone may not be written to ‘1’ even when using the AK
3. Requiring authentication automatically requires the use of secure checksums for write operations (See Section
Password Mode
Authentication Mode
When AM = "00", the POK bits in the corresponding password/key register are ignored
6.1.4, Encrypted Checksum (Message Authentication Code, MAC)
Registers). Verification of the write password also allows modification of the read and the write passwords.
AM0
PM1
1
0
1
0
1
0
*
Access
No password required
Write password required
Read and write passwords required
Access
No authentication required
Authentication for write
Normal authentication mode
Dual access mode
Atmel AT88SC0104CA/0204CA/0404CA/0808CA [Datasheet]
8664E−CRYPTO−12/11
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