at88sc0808ca ATMEL Corporation, at88sc0808ca Datasheet - Page 15

• Manufacturer Part Number: at88sc0808ca
• Description: Cryptomemory
• Manufacturer: ATMEL Corporation

13.6
13.7
13.8
13.9
14. Protocol Selection
14.1
5204BS–CRYPT–2/09
Encryption
Supervisor Mode
Modify Forbidden
Program Only
Synchronous 2-Wire Serial Interface
The data exchanged between the device and the host during read, write and verify password
commands may be encrypted to ensure data confidentiality.
The issuer may choose to require encryption for a user zone by settings made in the configura-
tion memory. Any one of four keys may be selected for use with a user zone. In this case,
activation of the encryption mode is required in order to read/write data in the zone and only
encrypted data will be transmitted. Even if not required, the host may still elect to activate
encryption provided the proper keys are known.
Enabling this feature allows the holder of one specific password to gain full access to all eight
password sets, including the ability to change passwords.
No write access is allowed in a user zone protected with this feature at any time. The user zone
must be written during device personalization prior to blowing the security fuses.
For a user zones protected by this feature, data can only be programmed (bits change from a “1”
to a “0”), but not erased (bits change from a “0” to a “1”).
The AT88SC0808CA supports two different communication protocols.
Smartcard Applications:
Smartcard applications use ISO 7816-B protocol in asynchronous T = 0 mode for compatibility
and interoperability with industry standard smartcard readers.
Embedded Applications:
A 2-wire serial interface provides fast and efficient connectivity with other logic devices or micro-
controllers.
The power-up sequence determines establishes the communication protocol for use within that
power cycle. Protocol selection is allowed only during power-up.
The synchronous mode is the default mode after power up. This is due to the presence of an
internal pull-up on RST. For embedded applications using CryptoMemory in standard plastic
packages, this is the only available communication protocol.
Power-up VCC, RST goes high also.
After stable VCC, SCL(CLK) and SDA(I/O) may be driven.
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