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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.
If a parity error occurs, however, the receiving station outputs an error signal (DE, low-level)
to request retransmission of the data. After outputting the error signal for the prescribed length
of time, the receiving station places the signal line in the high-impedance state again. The
signal line is pulled high again by a pull-up resistor.
[5] If the transmitting station does not receive an error signal, it proceeds to transmit the next data
frame.
If it does receive an error signal, however, it returns to step [2] and retransmits the erroneous
data.
(2) Block Transfer Mode
The operation sequence in block transfer mode is as follows.
[1] When the data line in 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] After reception, a parity error check is carried out, but an error signal is not output even if an
error has occurred. When an error occurs reception cannot be continued, so the error flag
should be cleared to 0 before the parity bit of the next frame is received.
[5] The transmitting station proceeds to transmit the next data frame.
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