H8S2245 datasheet(533/818 Pages) RENESAS

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Section 13 Smart Card Interface

Rev.3.00 Mar. 26, 2007 Page 491 of 772

REJ09B0355-0300

Serial Data Transmission

As data transmission in smart card mode involves error signal sampling and retransmission

processing, the processing procedure is different from that for the normal SCI. Figure 13.4 shows

a flowchart for transmitting, and figure 13.5 shows the relation between a transmit operation and

the internal registers.

[1] Perform Smart Card interface mode initialization as described above in Initialization.

[2] Check that the ERS error flag in SSR is cleared to 0.

[3] Repeat steps [2] and [3] until it can be confirmed that the TEND flag in SSR is set to 1.

[4] Write the transmit data to TDR, clear the TDRE flag to 0, and perform the transmit operation.

The TEND flag is cleared to 0.

[5] When transmitting data continuously, go back to step [2].

[6] To end transmission, clear the TE bit to 0.

With the above processing, interrupt servicing or data transfer by the DTC is possible.

If transmission ends and the TEND flag is set to 1 while the TIE bit is set to 1 and interrupt

requests are enabled, a transmit data empty interrupt (TXI) request will be generated. If an error

occurs in transmission and the ERS flag is set to 1 while the RIE bit is set to 1 and interrupt

requests are enabled, a transfer error interrupt (ERI) request will be generated.

The timing for setting the TEND flag depends on the value of the GM bit in SMR. The TEND flag

set timing is shown in figure 13.6.

If the DTC is activated by a TXI request, the number of bytes set in the DTC can be transmitted

automatically, including automatic retransmission.

For details, see Interrupt Operations and Data Transfer Operation by DTC below.

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