AT88SC0204CA-TU Atmel, AT88SC0204CA-TU Datasheet - Page 18

• Manufacturer Part Number: AT88SC0204CA-TU
• Manufacturer: Atmel

Specifications of AT88SC0204CA-TU

• Operating Temperature (max): 85C
• Operating Temperature (min): -40C
• Mounting: Surface Mount
• Pin Count: 8
• Operating Temperature Classification: Industrial
• Lead Free Status / RoHS Status: Compliant

6.2.
6.2.1. Modify Forbidden
6.2.2. Program Only
6.2.3. Write Lock
6.2.4. Anti-tearing (Power Loss Protection)
8664C–CRYPT–01/10
Data Protection Features
Security operations control access to data stored in Atmel
exist to protect data in the user memory.
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.
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.
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. Figure 8 shows the use of write lock for data at addresses $080 - $087. The byte at
$080 controls writeaccess to bytes from $080 to $087.
Table 8.
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.
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
8-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
Atmel AT88SC0104/0204/0404/0808/CA
$2
xxxx xxxx
$3
®
CryptoMemory
xxxx xxxx
$4
®
. After gaining access, additional options
xxxx xxxx
locked
$5
xxxx xxxx
$6
xxxx xxxx
$7
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