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CHAPTER 18 EXPANDED I/O SERIAL INTERFACE
18.3.1 Serial Mode Control Status Register 0/1 (SMCS0/SMCS1)
This section describes the configuration and functions of the serial mode control
status register0/1 (SMCS0/SMCS1).
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Serial mode control status register0/1 (SMCS0/SMCS1)
The serial mode control status register 0/1 (SMCS0/SMCS1) controls the data transfer mode of
serial I/O operations.
The bit configuration of the serial mode control status register 0/1 (SMCS0/SMCS1) is illustrated
below.
SMCS
address: 000027
ch.0
00002B
ch.1
SMCS
address: 000026
ch.0
00002A
ch.1
*1: Only "0" can be written
*2: Only "1" can be written. Reading always returns "0"
The functions of the bits of the serial mode control status register 0/1 (SMCS0/SMCS1) are
described below.
[bit15, bit14, bit13] SMD2, SMD1 and SMD0: Serial Shift Clock Mode (Shift clock select)
These bits select the serial shift clock mode. Table 18.3-1 shows the settings for the serial
shift clock mode.
Table 18.3-1 Settings of serial shift clock mode
Selection of serial shift clock mode
SMD2 SMD1 SMD0
0
0
0
0
1
1
1
1
390
15
14
13
H
SMD2 SMD1 SMD0 SIE
H
R/W
R/W
R/W R/W R/W
7
6
-
-
H
H
φ=16MHz φ=8MHz φ=4MHz
div=8
div=4
1MHz
1MHz
0
0
500kHz
0
1
500kHz
125kHz
1
0
125kHz
62.5kHz
62.5kHz
1
1
31.2kHz
31.2kHz
0
0
External shift clock mode
0
1
reserved
1
0
1
1
reserved
12
11
10
SIR BUSY STOP STRT
R
↑
*1
5
4
3
2
-
-
MODE BDS
R/W
R/W
Setting of communication prescaler (SDCR)
Division
Div
div=4
value
MD DIV3 DIV2 D1IV DIV0
500kHz
1
1
2
250kHz
2
1
4
62.5kHz
3
1
16
31.2kHz
4
1
32
15.6kHz
5
1
64
6
1
7
1
8
1
9
8
Initial value
00000010
B
R/W R/W
↑
*2
1
0
Initial value
SOE SCOE - - - -0000
B
R/W R/W
Recommended
(Machine clock)
machine clock
0
0
0
0
0
0
0
1
0
0
1
0
0
0
1
1
0
1
0
0
0
1
0
1
0
1
1
0
0
1
1
1
cycle
2MHz
4MHz
6MHz
8MHz
10MHz
12MHz
14MHz
16MHz
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