AT88SC0104C datasheet(39/58 Pages) ATMEL

39 / 58 page

5210B–SMIC–11/08

AT88SC0104/0204/0404/0808/1616/3216/6416/12816/25616C

After the ATR, the reader will have the choice of proceeding with commands using default val-

ues of F=372 and D=1 (9600 baud at 3.5712 MHz), or negotiating values Fn and Dn through a

PPS exchange. Following are four examples of PPS requests and responses:

8.3.1

Example 1

We assume the CryptoMemory ATR contains the byte TA(1) = 15h, indicating that it is capable

of using F=372 and D=16, leading to a baud rate of 153,600 baud at 3.5712 MHz. Assuming that

this is the maximum speed supported by the device, the reader immediately attempts to set the

F and D parameters leading to these values.

• PPS_request =$FF $10 $15 $FA

• PPS_response = $FF $10 $15 $FA

The newly negotiated values are effective immediately following this exchange, so that the ETU,

or duration of one bit on I/O, will now be 23 clock cycles instead of 372.

8.3.2

Example 2

The reader insists on negotiating Fn and Dn equal to the default values, even though these

would be used by default without the use of a PPS exchange. The two ways of doing this are by

sending PPS1_request = $11 or not sending PPS1_request at all.

• PPS_request = $FF $10 $11 $FE

• PPS_response= $FF $10 $11 $FE

• PPS_request= $FF $00 $FF

• PPS_response = $FF $00 $FF

8.3.3

Example 3

The reader attempts to negotiate values that are not supported by the CryptoMemory device. In

its response, the CryptoMemory proposes to continue with F and D, by not sending

PPS1_response. Even though new Fn and Dn values aren’t negotiated, this scenario is still con-

sidered a “successful” exchange according to ISO 7816.

• PPS_request= $FF $10 $45 $AA

• PPS_response= $FF $00 $FF

8.3.4

Example 4

If the reader attempts to change the protocol to any protocol other than T = 0, such as T = 1, the

CryptoMemory will indicate that it only supports T = 0.

• PPS_request= $FF $01 $FE

• PPS_response= $FF $00 $FF

AT88SC0104C Datasheet(PDF) 39 Page - ATMEL Corporation