AT88SC0104CA_11 ATMEL [ATMEL Corporation], AT88SC0104CA_11 Datasheet - Page 41

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

9.
9.1
9.2
9.3
9.4
Initialization Example
The first step in initializing CryptoMemory is to determine what data is to be stored in the device and what the security settings
need to be to protect this data. Once defined, determine the proper settings for CryptoMemory registers and select values for
passwords. To initialize the CryptoMemory device, the following sequence is recommended to take place in a secure location
to protect sensitive data and passwords that may be loaded into the device.
Write Data to User Zones
In the default configuration from Atmel, all user zones have free access rights. Writing initial data into the user zones should be
done before setting security configurations. Use the set user zone command and write user zone command to write initial data
into the user zones. The read user zone command may be used to verify the data written.
Unlock the Configuration Memory
Before any data can be written to the configuration zone, it must be unlocked by presenting the correct security code (Write 7
password). Use the verify password command with the proper secure code supplied by Atmel to unlock the configuration zone.
Use the read config zone command to read back the security code at address $E9 for verification that the configuration zone
has been unlocked.
Write Data to the Configuration Memory
Writing this data is accomplished by performing the write config zone command at the appropriate address location. The read
config zone command may be used to verify the data written. As soon as values are written to the registers, keys, and
passwords, they become effective in determining the security of the user zones.
Set Security Fuses
Once all data is written and verified into user zones and the configuration zone the security fuses should be set before the
device is released from the secure location used for device initialization. There are three fuses, FAB, CMA and PER that must
be set. These three fuses must be set in the order listed (FAB, then CMA, then PER). The write fuse command is used to set
each of the three fuses individually. The read fuse command may be used to check the status of all three fuses. Once all fuses
have been set the read fuse command should return a value of zero for the second nibble of the fuse byte.
The AT88SC0104CA is used for this example. A small pattern is written into the first two user zones. Security for each of these
two user zones and the associated register values are shown in the table below. Simple values for passwords are used.
Table 9-1.
User Zone
0
1
2
3
CryptoMemory Asynchronous Command Set
Zone 0
Zone 1
Zone 2
Zone 3
Data
Security Requirements
None
Read/Write Password (Set 1)
Read/Write Authentication (Set 2)
Read/Write Password (Set 1),
Read/Write Authentication (Set 2)
with encryption required
Atmel AT88SC0104CA/0204CA/0404CA/0808CA [Datasheet]
Access Register
$DF
$FF
$7F
$57
Password/Key Register
8664E−CRYPTO−12/11
$FF
$BF
$B9
$F9
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