AT88SC0104CA_11 ATMEL [ATMEL Corporation], AT88SC0104CA_11 Datasheet - Page 50

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

10.7.2 Write Config Zone
10.7.3 Write Fuses
10.7.4 Send Checksum
10.7.5 Set User Zone
The maximum number of bytes to write for each call of the write command is $16 and corresponds to the EEPROM page size.
Each data byte within a page must only be loaded once. In anti-tearing mode the maximum value for N is $08 for all devices.
If the address provided at P2 is an unauthorized address, the device will return the "Command Unauthorized" code ($69 $00)
after it has received the header. Since access rights vary throughout the configuration zone, the host may provide an
authorized starting address, but a number of bytes that causes the device to reach unauthorized data. In this case, the device
will prevent the internal write cycle and no bytes will be written in the EEPROM. At the end of the command the "Command
Unauthorized" code ($69 $00) will be returned instead of $90 $00 to indicate that no write cycle occurred.
Table 10-7. Fuse Bytes
The fuses may only be "programmed", that is written from '1' to '0'. The write fuses operation is only allowed after successfully
presenting the secure code (Write 7 password). The fuses must be blown sequentially: FAB must be blown first, CMA may be
blown only if FAB is ‘0’, and PER only if CMA is ‘0’. The SEC fuse is blown at the Atmel factory to protect lot history
information.
To write data to user zones that require authentication or encryption for write access (ER = “0”, AM [1:0] = “00”, “01”, or “10” in
the access register), the host should first carry out the write command $B0, after which the device will return a special status
word: $62 $00. At this point the memory is unchanged and the device is waiting for the host to provide a valid checksum
before initiating the write cycle. The host immediately sends the checksum it has computed using the system write command
with P1 = $02. Only if the checksum is valid will the device initiate the write cycle. Furthermore, if the device receives an
incorrect checksum, it will clear the authentication privilege. After this command the host must perform ACK polling.
Before reading and writing data in the user zones, the host should select a zone with this command. At this time the host may
choose whether anti-tearing should be active for this zone.
Table 10-8. System Write Command Structure
CLA
**
Fuse
CMA
SEC
PER
FAB
INS : Command
$B4
Fuse ID
$07
$06
$04
$00
Command Header
p
7
P1
--- p
0
Atmel AT88SC0104CA/0204CA/0404CA/0808CA [Datasheet]
p
7
P2
--- p
0
n
7
P3
--- n
0
d
Data(1)
7
--- ---d
0
8664E−CRYPTO−12/11
Data Sent
...
...
d
Data(N)
7
--- ---d
0
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