Datasheet

Section 17 Serial Communication Interface 3 (SCI3)
Rev. 3.00 Mar. 15, 2006 Page 331 of 526
REJ09B0060-0300
17.5.5 Simultaneous Serial Data Transmission and Reception
Figure 17.14 shows a sample flowchart for simultaneous serial transmit and receive operations.
The following procedure should be used for simultaneous serial data transmit and receive
operations. To switch from transmit mode to simultaneous transmit and receive mode, after
checking that the SCI3 has finished transmission and the TDRE and TEND flags are set to 1, clear
TE to 0. Then simultaneously set TE and RE to 1 with a single instruction. To switch from receive
mode to simultaneous transmit and receive mode, after checking that the SCI3 has finished
reception, clear RE to 0. Then after checking that the RDRF and receive error flags (OER, FER,
and PER) are cleared to 0, simultaneously set TE and RE to 1 with a single instruction.
Yes
<End>
No
Start transmission/reception
[3]
Error processing
[4]
Yes
No
[1]
Read TDRE flag in SSR
Write transmit data to TDR
Read OER flag in SSR
Read RDRF flag in SSR
No
Yes
TDRE = 1
OER = 1
RDRF = 1
Read receive data in RDR
Clear TE and RE bits in SCR to 0
All data received?
No
Yes
[2]
[1] Read SSR and check that the TDRE flag
is set to 1, then write transmit data to
TDR.
When data is written to TDR, the TDRE
flag is automatically cleared to 0.
[2] Read SSR and check that the RDRF flag
is set to 1, then read the receive data in
RDR.
When data is read from RDR, the RDRF
flag is automatically cleared to 0.
[3] To continue serial transmission/
reception, before the MSB (bit 7) of the
current frame is received, finish reading
the RDRF flag, reading RDR. Also,
before the MSB (bit 7) of the current
frame is transmitted, read 1 from the
TDRE flag to confirm that writing is
possible. Then write data to TDR.
When data is written to TDR, the TDRE
flag is automatically cleared to 0. When
data is read from RDR, the RDRF flag is
automatically cleared to 0.
[4] If an overrun error occurs, read the OER
flag in SSR, and after performing the
appropriate error processing, clear the
OER flag to 0. Transmission/reception
cannot be resumed if the OER flag is set
to 1.
For overrun error processing, see figure
17.13.
Figure 17.14 Sample Flowchart of Simultaneous Serial Transmit and Receive Operations
(Clocked Synchronous Mode)