AT88SC0404CA-SH Atmel, AT88SC0404CA-SH Datasheet - Page 17

• Manufacturer Part Number: AT88SC0404CA-SH
• Description: EEPROM CryptoMemory, 4Kbit, 4Zone, 8SOIC, GRN
• Manufacturer: Atmel

Specifications of AT88SC0404CA-SH

• Rohs: yes
• Factory Pack Quantity: 12000

6.2
6.2.1
6.2.2
6.2.3
6.2.4
Data Protection Features
Security operations control access to data stored in CryptoMemory. After gaining access, additional options exist to protect
data in the user memory.
Modify Forbidden
The Modify Forbidden option renders the user zone read-only by restricting all write operations to it. It is recommended to
program all required data in the user zone prior to enabling this option. Modify forbidden is available for any user zone and is
selectable by configuring appropriate access registers.
Program Only
The program only option constrains data bit modification to programming from logic “1” to logic “0” only. Data bits may never
change from logic “0” to logic “1”. Program only is available for any user zone and is selectable by configuring appropriate
access registers.
Write Lock
The write lock option provides ability to render individual bytes within a user zone read-only by restricting all write operations to
it. It operates on 8-byte page level whereby the lowest addressed byte of the page serves as the write access control byte for
that page. Table 6-2 shows the use of write lock for data at addresses $080 - $087. The byte at $080 controls write access to
bytes from $080 to $087.
Table 6-2.
The write lock option also applies to the access control byte for each page by writing its least significant (rightmost) bit to logic
“0”. Moreover, only logic modifications from logic “1” to logic “0” of the access control byte are permissible. Write lock is
available for any user zone and is selectable by configuring appropriate access registers. Furthermore, configuring a user
zone with the write lock option restricts writing to that zone to a byte at a time. Attempts to write several bytes within a
command; results in writing only the first byte.
Anti-tearing (Power Loss Protection)
In the event of a power loss during a write cycle, the integrity of the device's stored data may be recovered. This function is
optional, and the host may choose to activate the anti-tearing function for any write to a user zone or configuration zone by use
of the appropriate B4 system write command. When anti-tearing is active, write commands will take longer to execute since
more write cycles are required. Additionally, the data written is limited to eight bytes.
Data is written first to a buffer zone in EEPROM instead of the intended destination address in the user zone or configuration
zone, but with the same access conditions. If this write cycle is interrupted the original data remains intact in the user zone or
configuration zone. The data is then written in the required memory location. If this second write cycle is interrupted the device
will automatically recover the data from the system buffer zone at the next power-up and write it to the intended destination
address.
In two-wire mode, the host is required to perform ack polling for 36ms after write commands when anti-tearing is active. At
power-up five clock cycles are required to check the anti-tearing flags. In the event that the device needs to carry out the data
recovery process the host is required to perform ack polling for 18ms.
Address
$080
Write Lock example
11011001
$0
xxxx xxxx
locked
$1
xxxx xxxx
locked
$2
Atmel AT88SC0104CA/0204CA/0404CA/0808CA [Datasheet]
xxxx xxxx
$3
xxxx xxxx
$4
xxxx xxxx
locked
$5
xxxx xxxx
8664E−CRYPTO−12/11
$6
xxxx xxxx
$7
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