AT88SC0404C-PI Atmel, AT88SC0404C-PI Datasheet - Page 22

• Manufacturer Part Number: AT88SC0404C-PI
• Manufacturer: Atmel

Specifications of AT88SC0404C-PI

• Operating Temperature (max): 85C
• Operating Temperature (min): -40C
• Package Type: PDIP
• Mounting: Through Hole
• Pin Count: 8
• Operating Temperature Classification: Industrial
• Lead Free Status / RoHS Status: Not Compliant

5.3.9. Access Registers
5211C–SMIC–01/10
Atmel AT88SC0104/0204/0404/0808/1616/3216/6416/12816/25616C
Four, eight, or sixteen 8-bit access registers allow personalization of the device. Each access register works in
conjunction with a Password/Key register to define the security settings for each individual zone of the user memory.
Values in the access registers take immediate effect after programming. The default value for each bit is “1”.
Table 17. Access Register
PM(1:0) Password Mode
Table 18. Password Mode
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 following section). Verification of the write password also allows modification of the read and the write passwords,
for each password set.
AM(1:0) – Authentication mode
Table 19. Authentication Mode
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 following section).
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 Authentication Key (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 on the Passwords/Keys Register for further definition of POK
and AK.
Note:
Bit 7
PM1
PM0
AM1
1
1
0
1
1
0
0
1. When AM = "00", the POK bits in the corresponding Password/Key Register are ignored
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
“Encrypted
Bit 6
PM0
PM1
AM0
1
0
1
0
1
0
*
Checksum” on page 17)
No Password required
Write Password required
Read and Write Passwords required
No Authentication required
Authentication for Write
Normal Authentication Mode
Dual Access Mode
Bit 5
AM1
Access
Access
Bit 4
AM0
Bit 3
ER
WLM
Bit 2
Bit 1
MDF
Bit 0
PGO
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