Datasheet

Section 14 Serial Communication Interface 3 (SCI3)
Rev. 6.00 Mar. 24, 2006 Page 223 of 412
REJ09B0142-0600
14.5.5 Simultaneous Serial Data Transmission and Reception
Figure 14.14 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]
Read receive data in RDR
Yes
No
OER = 1
All data received?
[1]
Read TDRE flag in SSR
No
Yes
TDRE = 1
Write transmit data to TDR
No
Yes
RDRF = 1
Read OER flag in SSR
[2]
Read RDRF flag in SSR
Clear TE and RE bits in SCR to 0
[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 14.13.
Figure 14.14 Sample Flowchart of Simultaneous Serial Transmit and Receive Operations
(Clocked Synchronous Mode)