3

AT88SC1608

0971G–SMEM–04/04

Memory Access

Depending on the device configuration, the host might carry out the authentication pro-

tocol and/or present different passwords for each operation, read or write. Each user

zone may be configured for free access for read and write or for password-restricted

access. To insure security between the different user zones (multiapplication card),

each zone can use a different set of passwords. A specific AAC for each password and

for the authentication provides protection against “systematic attacks.” When the mem-

ory is unlocked, the two-wire serial protocol is effective, using SDA and SCL. The

memory includes a specific register providing a 32-bit data stream conforming to the

ISO 7816-10 synchronous answer-to-reset.

Figure 2. Block Diagram

Pin Descriptions

Supply Voltage (VCC)

The V

Serial Clock (SCL)

The SCL input is used to positive edge clock data into the device and negative edge

clock data out of the device.

Serial Data (SDA)

The SDA pin is bidirectional for serial data transfer. This pin is open-drain driven and

may be wire-ORed with any number of other open drain or open collector devices. An

external pull-up resistor should be connected between SDA and VCC. The value of this

resistor and the system capacitance loading the SDA bus will determine the rise time of

SDA. This rise time will determine the maximum frequency during read operations. Low

value pull-up resistors will allow higher frequency operations while drawing higher aver-

age power supply current.

Reset (RST)

When the RST input is pulsed high, the device will output the data programmed into the

32-bit answer-to-reset register. All password and authentication access will be reset.

Following a reset, device authentication and password verification sequences must be

presented to re-establish user access.

VCC

GND

SCL

SDA

RST

ISO

Interface

Power

Mgt.

Authentication

Unit

Data

Transfer

Password

Verification

Answer

To Reset

EEPROM

Random

Generator