HD6413007F20 Datasheet, PDF (532/798 Pages) Renesas Technology Corp – Hardware Manual Renesas 16-Bit Single-Chip Microcomputer H8 Family/H8/300H Series

14. Smart Card Interface
Transmitting Serial Data: 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 14.5 shows a sample transmission processing flowchart.
1. Perform smart card interface mode initialization as described in Initialization above.
2. Check that the ERS error flag is cleared to 0 in SSR.
3. Repeat steps 2 and 3 until it can be confirmed that the TEND flag is set to 1 in SSR.
4. Write the transmit data in TDR, clear the TDRE flag to 0, and perform the transmit operation.
The TEND flag is cleared to 0.
5. To continue transmitting data, go back to step 2.
6. To end transmission, clear the TE bit to 0.
The above processing may include interrupt handling DMA transfer.
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) will be requested. 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 transmit/receive-error interrupt (ERI) will be requested.
The timing of TEND flag setting depends on the GM bit in SMR (see figure 14.4).
If the TXI interrupt activates the DMAC, the number of bytes designated in the DMAC can be
transmitted automatically, including automatic retransmission.
For details, see Interrupt Operations and Data Transfer by DMAC in this section.
Serial data
Ds
(1) GM = 0
TEND
12.5 etu
Dp DE
Guard time
(2) GM = 1
TEND
11.0 etu
Figure 14.4 Timing of TEND Flag Setting
Rev.5.00 Sep. 12, 2007 Page 502 of 764
REJ09B0396-0500