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Section 13 Serial Communication Interface (SCI)
Start transmission/reception
No
Write transmit data to TDR and
clear TDRE flag in SSR to 0
Read ORER flag in SSR
No
Read receive data in RDR, and
clear RDRF flag in SSR to 0
No
Clear TE and RE bits in SCR to 0
Note: When switching from transmit or receive operation to simultaneous
transmit and receive operations, first clear the TE bit and RE bit to 0,
then set both these bits to 1 simultaneously.
Figure 13.20 Sample Flowchart of Simultaneous Serial Transmission and Reception
Rev. 1.00 Mar. 12, 2008 Page 474 of 1178
REJ09B0403-0100
Initialization
Read TDRE flag in SSR
TDRE = 1
Yes
ORER = 1
No
Read RDRF flag in SSR
RDRF = 1
Yes
All data received?
Yes
<End>
[1] SCI initialization:
[1]
[2]
[2] SCI status check and transmit data
[3] Receive error processing:
Yes
[3]
[4] SCI status check and receive data
Error processing
[4]
[5] Serial transmission/reception
[5]
The TxD pin is designated as the
transmit data output pin, and the RxD
pin is designated as the receive data
input pin, enabling simultaneous
transmit and receive operations.
write:
Read SSR and check that the TDRE
flag is set to 1, then write transmit
data to TDR and clear the TDRE flag
to 0.
Transition of the TDRE flag from 0 to
1 can also be identified by a TXI
interrupt.
If a receive error occurs, read the
ORER flag in SSR, and after
performing the appropriate error
processing, clear the ORER flag to 0.
Transmission/reception cannot be
resumed if the ORER flag is set to 1.
read:
Read SSR and check that the RDRF
flag is set to 1, then read the receive
data in RDR and clear the RDRF flag
to 0. Transition of the RDRF flag from
0 to 1 can also be identified by an RXI
interrupt.
continuation procedure:
To continue serial transmission/
reception, before the MSB (bit 7) of
the current frame is received, finish
reading the RDRF flag, reading RDR,
and clearing the RDRF flag to 0. 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 and
clear the TDRE flag to 0.
However, the TDRE flag is checked
and cleared automatically when the
DTC is initiated by a transmit data
empty interrupt (TXI) request and
writes data to TDR. Similarly, the
RDRF flag is cleared automatically
when the DTC is initiated by a receive
data full interrupt (RXI) and reads
data from RDR.
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