SH7014 Datasheet, PDF (394/754 Pages) Renesas Technology Corp – 32-Bit RISC Microcomputer

12. Serial Communication Interface (SCI)
In receiving, the SCI operates as follows:
1. The SCI synchronizes with serial clock input or output and initializes internally.
2. Receive data is shifted into the RSR in order from the LSB to the MSB. After receiving the
data, the SCI checks that RDRF is 0 so that receive data can be loaded from the RSR into the
RDR. If this check passes, the SCI sets RDRF to 1 and stores the received data in the RDR. If
the check does not pass (receive error), the SCI operates as indicated in table 12.11 and no
further transmission or reception is possible. If the error flag is set to 1, the RDRF bit is not set
to 1 during reception, even if the RDRF bit is 0 cleared. When restarting reception, be sure to
clear the error flag.
3. After setting RDRF to 1, if the receive-data-full interrupt enable bit (RIE) is set to 1 in the
SCR, the SCI requests a receive-data-full interrupt (RXI). If the ORER bit is set to 1 and the
receive-data-full interrupt enable bit (RIE) in the SCR is also set to 1, the SCI requests a
receive-error interrupt (ERI).
Transmitting and Receiving Serial Data Simultaneously (Clock Synchronous Mode): Figure
12.20 shows a sample flowchart for transmitting and receiving serial data simultaneously. The
procedure is as follows (the steps correspond to the numbers in the flowchart):
1. SCI initialization: Set the TxD and RxD pins using the PFC.
2. SCI status check and transmit data write: Read the serial status register (SSR), check that the
TDRE bit is 1, then write transmit data in the transmit data register (TDR) and clear TDRE to
0. The TXI interrupt can also be used to determine if the TDRE bit has changed from 0 to 1.
3. Receive error handling: If a receive error occurs, read the ORER bit in SSR to identify the
error. After executing the necessary error processing, clear ORER to 0. Transmitting/receiving
cannot resume if ORER remains set to 1.
4. SCI status check and receive data read: Read the serial status register (SSR), check that RDRF
is set to 1, then read receive data from the receive data register (RDR) and clear RDRF to 0.
The RxI interrupt can also be used to determine if the RDRF bit has changed from 0 to 1.
5. Continue transmitting and receiving serial data: Read the RDRF bit and RDR, and clear RDRF
to 0 before the frame MSB (bit 7) of the current frame is received. Also read the TDRE bit to
check whether it is safe to write (if it reads 1); if so, write data in TDR, then clear TDRE to 0
before the MSB (bit 7) of the current frame is transmitted. When the DMAC is started by a
transmit-data-empty interrupt request (TXI) to write data in TDR, the TDRE bit is checked and
cleared automatically. When the DMAC is started by a receive-data-full interrupt (RXI) to read
RDR, the RDRF bit is cleared automatically.
Note: In switching from transmitting or receiving to simultaneous transmitting and receiving,
simultaneously clear the TE bit and RE bit to 0, then simultaneously set the TE bit and RE
bit to 1.
Rev.5.00 Sep. 27, 2007 Page 360 of 716
REJ09B0398-0500