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For serial communication interface (SMIF bit in SCMR cleared to 0): These bits select the
SCI clock source and enable or disable clock output from the SCK pin. Depending on the settings
of CKE1 and CKE0, the SCK pin can be used for generic input/output, serial clock output, or
serial clock input.
The CKE0 setting is valid only in asynchronous mode, and only when the SCI is internally
clocked (CKE1 = 0). The CKE0 setting is ignored in synchronous mode, or when an external
clock source is selected (CKE1 = 1). Select the SCI operating mode in SMR before setting the
CKE1 and CKE0 bits . For further details on selection of the SCI clock source, see table 12.9 in
section 12.3, Operation.
Bit 1
Bit 0
CKE1
CKE0 Description
0
0
Asynchronous mode
Synchronous mode
0
1
Asynchronous mode
Synchronous mode
1
0
Asynchronous mode
Synchronous mode
1
1
Asynchronous mode
Synchronous mode
Notes: 1. Initial value
2. The output clock frequency is the same as the bit rate.
3. The input clock frequency is 16 times the bit rate.
For smart card interface (SMIF bit in SCMR set to 1): These bits, together with the GM bit in
SMR, determine whether the SCK pin is used for generic input/output or as the serial clock output
pin.
SMR
Bit 1
Bit 0
GM
CKE1
CKE0 Description
0
0
0
0
0
1
1
0
0
1
0
1
1
1
0
1
1
1
370
Internal clock, SCK pin available for generic input/output*
Internal clock, SCK pin used for serial clock output*
Internal clock, SCK pin used for clock output*
Internal clock, SCK pin used for serial clock output
External clock, SCK pin used for clock input*
External clock, SCK pin used for serial clock input
External clock, SCK pin used for clock input*
External clock, SCK pin used for serial clock input
SCK pin available for generic input/output
SCK pin used for clock output
SCK pin output fixed low
SCK pin used for clock output
SCK pin output fixed high
SCK pin used for clock output
1
1
2
3
3
(Initial value)
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