Datasheet

Section 15 Serial Communication Interface (SCI)
Rev. 6.00 Mar. 18, 2010 Page 614 of 982
REJ09B0054-0600
after checking that the SCI has finished transmission, initialize the SCI, and set TE to 0 and RE to
1. Whether SCI has finished transmission or not can be checked with the TEND flag.
15.7.6 Serial Data Transmission (Except for Block Transfer Mode)
As data transmission in Smart Card interface mode involves error signal sampling and
retransmission processing, the operations are different from those in normal serial communication
interface mode (except for block transfer mode). Figure 15.29 illustrates the retransfer operation
when the SCI is in transmit mode.
1. If an error signal is sent back from the receiving end after transmission of one frame is
complete, the ERS bit in SSR is set to 1. If the RIE bit in SCR is enabled at this time, an ERI
interrupt request is generated. The ERS bit in SSR should be cleared to 0 by the time the next
parity bit is sampled.
2. The TEND bit in SSR is not set for a frame in which an error signal indicating an abnormality
is received. Data is retransferred from TDR to TSR, and retransmitted automatically.
3. If an error signal is not sent back from the receiving end, the ERS bit in SSR is not set.
Transmission of one frame, including a retransfer, is judged to have been completed, and the
TEND bit in SSR is set to 1. If the TIE bit in SCR is enabled at this time, a TXI interrupt
request is generated. Writing transmit data to TDR transfers the next transmit data.
Figure 15.31 shows a flowchart for transmission. A sequence of transmit operations can be
performed automatically by specifying the DTC to be activated with a TXI interrupt source. In a
transmit operation, the TDRE flag is set to 1 at the same time as the TEND flag in SSR is set, and
a TXI interrupt will be generated if the TIE bit in SCR has been set to 1. If the TXI request is
designated beforehand as a DTC activation source, the DTC will be activated by the TXI request,
and transfer of the transmit data will be carried out. At this moment, if DISEL in DTC is 0 with
the transfer counter not being 0, the TDRE and TEND flags are automatically cleared to 0 when
data is transferred by the DTC. When DISEL is 1, or DISEL is 0 with the transfer counter being 0,
the DTC writes the transfer data to the TDR but does not clear the flag. Therefore, the flag should
be cleared by CPU. In addition, in the event of the error, the SCI retransmits the same data
automatically. During this period, the TEND flag remains cleared to 0 and the DTC is not
activated. Therefore, the SCI and DTC will automatically transmit the specified number of bytes
in the event of an error, including retransmission. However, the ERS flag is not cleared
automatically when an error occurs, and so the RIE bit should be set to 1 beforehand so that an
ERI request will be generated in the event of an error, and the ERS flag will be cleared.
When performing transfer using the DTC, it is essential to set and enable the DTC before carrying
out SCI setting. For details of the DTC setting procedures, refer to section 9, Data Transfer
Controller (DTC).