HD64F2357F20V Datasheet, PDF (555/1049 Pages) Renesas Technology Corp – Hardware Manual Renesas 16-Bit Single-chip Microcomputer H8S Family / H8S/2300 Series

15.3.3 Data Format
Figure 15-3 shows the 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 D0 D1 D2 D3 D4 D5 D6 D7 Dp
Transmitting station output
When a parity error occurs
Ds D0 D1 D2 D3 D4 D5 D6 D7 Dp
DE
Legend:
Ds:
Start bit
D0 to D7:Data bits
Dp:
Parity bit
DE:
Error signal
Transmitting station output
Receiving station
output
Figure 15-3 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.
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.
Rev.6.00 Oct.28.2004 page 525 of 1016
REJ09B0138-0600H