AT88SC0104CA_08 Datasheet, PDF (7/58 Pages) ATMEL Corporation – CryptoMemory Specification for Standard Mode of Operation

4. Pin Description
4.1 Supply Voltage (V_CC)
The V_CC input is a 2.7V to 3.6V positive voltage supplied by the host.
4.2 Clock (SCL/CLK)
In the asynchronous T=0 protocol, the SCL/CLK input is used to provide the device with a carrier
frequency f. The nominal length of one bit emitted on I/O is defined as an "elementary time unit"
(etu) and is equal to 372/f. When the synchronous protocol is used, the SCL/CLK input is used
to clock data in on the positive clock edge and clock data out on the negative clock edge.
4.3 Serial Data (SDA/IO)
The SDA pin is bi-directional for serial data transfer. This pin is open-drain driven and may be
wired with any number of other open drain or open collector devices. An external pull up resistor
should be connected between SDA and V_CC, a nominal value of 4.7K ohm may be used. 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 average
power supply current.
4.4 Reset (RST)
CryptoMemory provides an ISO 7816-3 compliant asynchronous Answer-To-Reset (ATR)
sequence. When the reset sequence is activated, the device will output the data programmed
into the 64-bit answer to reset register. When RST is low, all internal logic, access rights and
write cycles are in reset, except the asynchronous mode activation flag. A weak internal pull-up
on the RST input pad allows the device to be used in synchronous mode without bonding RST.
For synchronous only smart card applications an external pull-up on RST is recommended to
ensure synchronous operation under any system timings or conditions. CryptoMemory does not
support a synchronous answer to reset sequence. The RST input is not available in the plastic
package options for CryptoMemory.
4.5 Detailed Description
To enable the security features of CryptoMemory, personalize the device by setting up registers
and loading appropriate passwords and keys. This is accomplished though programming the
configuration zone of CryptoMemory using simple write and read commands. To gain access to
the configuration zone, the secure code (write 7 password) must be successfully presented.
After writing and verifying data in the configuration zone, the security fuses must be blown to
lock this information in the device. For additional information on personalizing CryptoMemory,
please see the examples in the protocol sections of this specification.
4.6 User Memory
The EEPROM user memory is divided into 4 or 8 user zones. Multiple zones allow for the stor-
age of different data types or files in different zones. Access to user zones is possible only after
meeting security requirements. The customer defines these security requirements in the config-
uration zone during device personalization. When the same security requirements define access
to multiple zones, the zones effectively serve as one large storage area albeit with the require-
ment to select each zone prior to access.
7 AT88SCXXXXCA
5221A–CRYPT–10/08