13

5200AS–CRYPT–7/08

AT88SC0104CA

12.6

Encryption

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.

12.7

Supervisor Mode

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.

12.8

Modify Forbidden

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.

12.9

Program Only

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”).

13. Protocol Selection

The AT88SC0104CA supports two different communication protocols.

Smartcard Applications:

Smartcard applications use ISO 7816-B protocol in asynchronous T = 0 mode for compatibil-

ity and interoperability with industry standard smartcard readers.

Embedded Applications:

A 2-wire serial interface provides fast and efficient connectivity with other logic devices or

microcontrollers.

The power-up sequence determines establishes the communication protocol for use within that

power cycle. Protocol selection is allowed only during power-up.

13.1

Synchronous 2-Wire Serial Interface

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.