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14.3.3
Data Format
Normal Transfer Mode: Figure 14-3 shows the normal Smart Card interface data format. In
reception in this mode, a parity check is carried out on each frame, and if an error is detected an
error signal is sent back to the transmitting end, and retransmission of the data is requested. If an
error signal is sampled during transmission, the same data is retransmitted.
When there is no parity error
Ds
When a parity error occurs
Ds
Legend
Ds
: Start bit
D0 to D7
: Data bits
Dp
: Parity bit
DE
: Error signal
Figure 14-3 Normal Smart Card Interface Data Format
The operation sequence is as follows.
[1] When the data line is not in use it is in the high-impedance state, and is fixed high with a pull-
up resistor.
[2] The transmitting station starts transfer of one frame of data. The data frame starts with a start
bit (Ds, low-level), followed by 8 data bits (D0 to D7) and a parity bit (Dp).
[3] With the Smart Card interface, the data line then returns to the high-impedance state. The data
line is pulled high with a pull-up resistor.
[4] The receiving station carries out a parity check.
If there is no parity error and the data is received normally, the receiving station waits for
reception of the next data.
512
D0
D1
D2
D3
Transmitting station output
D0
D1
D2
D3
Transmitting station output
D4
D5
D6
D7
D4
D5
D6
D7
Dp
Dp
DE
Receiving station
output
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