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Bit 3: Clock source select 3 (CKS3)
Bit 3 selects the clock source to be supplied and sets the SCK
1
to input or output mode.
Bit 3
CKS3
Description
0
Clock source is prescaler S, SCK
1
is output
(initial value)
1
Clock source is external clock, SCK
1
is input
*
Note:
*
SCI1 is an internal function that performs interfacing to the on-chip FLEX™ decoder. It
cannot be used with SCK1 input selected.
Bits 2 to 0: Clock select 2 to 0 (CKS2 to CKS0)
When CKS3 is cleared to 0, bits 2 to 0 selects the prescaler division ratio and the serial clock
cycle.
Bit 2
Bit 1
Bit 0
Serial Clock Cycle
CKS2
CKS1
CKS0
Prescaler Division Ratio
ø = 2.5 MHz
0
0
0
ø/1024 (initial value)
409.6 µs
0
0
1
ø/256
102.4 µs
0
1
0
ø/64
25.6 µs
0
1
1
ø/32
12.8 µs
1
0
0
ø/16
6.4 µs
1
0
1
ø/8
3.2 µs
1
1
0
ø/4
1.6 µs
1
1
1
ø
W
/4
50 µs or 104.2 µs
2. Serial control status register 1 (SCSR1)
Bit
Initial value
Read/Write
7
—
1
—
6
SOL
0
R/W
5
ORER
0
R/(W)
*
4
—
1
—
3
—
1
—
0
STF
0
R/W
2
—
1
—
1
MTRF
0
R
Note:
*
Only a write of 0 for flag clearing is possible.
SCSR1 is an 8-bit register that indicates the operational and error status of SCI1.
Upon reset, SCSR1 is initialized to H'9C.
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