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Rev. 1.00, 05/04, page 270 of 544
Yes
<End>
[1]
No
Initialization
Start transmission/reception
[5]
Error processing
[3]
Read receive data in RDR, and
clear RDRF flag in SSR to 0
No
Yes
ORER = 1
All data received?
[2]
Read TDRE flag in SSR
No
Yes
TDRE = 1
Write transmit data to TDR and
clear TDRE flag in SSR to 0
No
Yes
RDRF = 1
Read ORER flag in SSR
[4]
Read RDRF flag in SSR
Clear TE and RE bits in SCR to 0
[1] SCI initialization:
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.
[2] SCI status check and transmit
data 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.
[3] Receive error processing:
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.
[4] SCI status check and receive
data 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.
[5] Serial transmission/reception
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
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 12.20 Sample Flowchart of Simultaneous Serial Transmission and Reception