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45.3.3 Clock and Transfer Attributes Register (In Master Mode)
(SPIx_CTARn)
CTAR registers are used to define different transfer attributes. Do not write to the CTAR
registers while the module is in the Running state.
In Master mode, the CTAR registers define combinations of transfer attributes such as
frame size, clock phase and polarity, data bit ordering, baud rate, and various delays. In
slave mode, a subset of the bitfields in CTAR0 are used to set the slave transfer attributes.
When the module is configured as a SPI master, the CTAS field in the command portion
of the TX FIFO entry selects which of the CTAR registers is used. When the module is
configured as an SPI bus slave, it uses the CTAR0 register.
Address: Base a Ch (4d × i), where i=0d to 1d
Bit
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
R
W
Reset
0
1
1
1
1
0
0
0
0
0
0
0
0
0
0
0
Bit
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
R
W
Reset
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
SPIx_CTARn field descriptions
Field
Description
31
DBR
Double Baud Rate
Doubles the effective baud rate of the Serial Communications Clock (SCK). This field is used only in
master mode. It effectively halves the Baud Rate division ratio, supporting faster frequencies, and odd
division ratios for the Serial Communications Clock (SCK). When the DBR bit is set, the duty cycle of the
Serial Communications Clock (SCK) depends on the value in the Baud Rate Prescaler and the Clock
Phase bit as listed in the following table. See the BR field description for details on how to compute the
baud rate.
Table 45-2. SPI SCK Duty Cycle
DBR
CPHA
PBR
SCK Duty Cycle
0
any
any
50/50
1
0
00
50/50
1
0
01
33/66
1
0
10
40/60
Table continues on the next page...
Memory Map/Register Definition
K22F Sub-Family Reference Manual, Rev. 4, 08/2016
1136
NXP Semiconductors
Содержание K22F series
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