AT88SC0104CA_11 ATMEL [ATMEL Corporation], AT88SC0104CA_11 Datasheet - Page 44

• Manufacturer Part Number: AT88SC0104CA_11
• Description: Atmel CryptoMemory Specification Datasheet
• Manufacturer: ATMEL [ATMEL Corporation]

10.
10.1
10.2
Asynchronous T=0 Protocol
Character Format
The CryptoMemory complies with the asynchronous T=0 protocol defined in ISO 7816-3. The character format is shown in the
following figure. Note that the byte is transmitted with the least significant bit first.
Figure 10-1. Character Format
I/O
Even parity is used: the parity bit is such that the overall sum of bits in the data byte and the parity bit is an even number. If a
transmission error is detected, the receiving device indicates this by applying a low level on the I/O channel during the guard
time. This tells the transmitting device to retransmit the byte.
Command format
The command sequence is as follows:
A
Z
1.
2.
3.
4.
Start bit
In compliance with ISO 7816-3, the host must send the header consisting of five characters: CLA, INS, P1, P2, P3
The device replies with a "procedure byte” normally equal to the INS code received. If a problem occurred, then the
Data transfer (P3 bytes)
A final SW1-SW2 sequence gives the status of the device after completion of the command. A normal completion is
device will respond with a status word pair SW1-SW2, indicating the end of the command
indicated by SW1-SW2 = $90-$00
Note:
•
•
•
•
0
CLA refers to a class of instructions. This byte isn't tested by the device
INS is the instruction byte
P1 and P2 are reference bytes, such as a data byte address or password index
P3 is the number of data bytes transferred during the command. For outgoing transfers (e.g. read commands),
P3 = 0 means that 256 data bytes will be emitted by the card. For incoming commands, P3 = 0 means that no
data bytes will be transferred
For all bytes transmitted by the device or by the host, including header, procedure, status and data bytes, if
a parity error is detected, the receiver requests that byte to be sent again (see character format)
t
d
1
0
d
1
(n ± 0,2) etu
d
2
8 data bits
d
3
d
4
d
5
Atmel AT88SC0104CA/0204CA/0404CA/0808CA [Datasheet]
d
6
t
d
n
7
Parity bit
p
t
Guard Time
10
Next Start bit
8664E−CRYPTO−12/11
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