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14.3 Operation
14.3.1 Overview
The SCI supports serial data transfer in both asynchronous and synchronous modes.
The communication format depends on settings in the SMR as indicated in table 14-5. The clock
source and usage of the SCK pin depend on settings in the SMR and SCR as indicated in table 14-6.
Table 14-5 Communication Formats Used by SCI
C/A
CHR
0
0
1
1
—
Table 14-6 SCI Clock Source Selection
SMR
C/A
CKE1
0
0
(Async
mode)
1
1
0
(Sync
mode)
1
* Cannot be used by the SCI.
Transmitting and receiving operations in the two modes are described next.
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SMR
PE
STOP
Mode
0
0
Asynchronous
1
1
0
1
0
0
1
1
0
1
—
—
Synchronous
SCR
Clock
CKE0
Source
0
Internal
1
0
External
1
0
Internal
1
0
External
1
Format
8-Bit data
7-Bit data
8-Bit data
SCK Pin
I/O port*
Clock output at same frequency as baud rate
Clock input at 16 times the baud rate frequency
Serial clock output
Serial clock input
259
Stop Bit
Parity
Length
None
1
2
Yes
1
2
None
1
2
Yes
1
2
—
—
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