Renesas H8S/2318 series, Hardware Manual

Page: 535 / 1121

Rev. 5.00, 12/03, page 505 of 1088
Serial Data Transmission (Except Block Transfer Mode): 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 handling 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 transmit/receive-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 setting 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.
Note: For details of operation in block transfer mode, see section 12.3.2, Operation in
Asynchronous Mode.