HD6417750 Datasheet, PDF (764/1039 Pages) Renesas Technology Corp – SuperH RISC engine

17.3.3 Data Format
Figure 17.3 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
side to request retransmission of the data. If an error signal is detected 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
Transmitting station output
Ds: Start bit
D0–D7: Data bits
Dp: Parity bit
DE: Error signal
DE
Receiving
station
output
Figure 17.3 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 transmission 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.
Rev. 6.0, 07/02, page 712 of 986