eUSCI_B SPI Registers
816
SLAU367P – October 2012 – Revised April 2020
Copyright © 2012–2020, Texas Instruments Incorporated
Enhanced Universal Serial Communication Interface (eUSCI) – SPI Mode
31.5.1 UCBxCTLW0 Register
eUSCI_Bx Control Register 0
Figure 31-13. UCBxCTLW0 Register
15
14
13
12
11
10
9
8
UCCKPH
UCCKPL
UCMSB
UC7BIT
UCMST
UCMODEx
UCSYNC
rw-0
rw-0
rw-0
rw-0
rw-0
rw-0
rw-0
rw-1
7
6
5
4
3
2
1
0
UCSSELx
Reserved
UCSTEM
UCSWRST
rw-1
rw-1
r0
rw-0
rw-0
rw-0
rw-0
rw-1
Can be modified only when UCSWRST = 1.
Table 31-12. UCBxCTLW0 Register Description
Bit
Field
Type
Reset
Description
15
UCCKPH
RW
0h
Clock phase select
0b = Data is changed on the first UCLK edge and captured on the following
edge.
1b = Data is captured on the first UCLK edge and changed on the following
edge.
14
UCCKPL
RW
0h
Clock polarity select
0b = The inactive state is low.
1b = The inactive state is high.
13
UCMSB
RW
0h
MSB first select. Controls the direction of the receive and transmit shift register.
0b = LSB first
1b = MSB first
12
UC7BIT
RW
0h
Character length. Selects 7-bit or 8-bit character length.
0b = 8-bit data
1b = 7-bit data
11
UCMST
RW
0h
Master mode select
0b = Slave mode
1b = Master mode
10-9
UCMODEx
RW
0h
eUSCI mode. The UCMODEx bits select the synchronous mode when UCSYNC
= 1.
00b = 3-pin SPI
01b = 4-pin SPI with UCxSTE active high: Slave enabled when UCxSTE = 1
10b = 4-pin SPI with UCxSTE active low: Slave enabled when UCxSTE = 0
11b = I2C mode
8
UCSYNC
RW
1h
Synchronous mode enable
0b = Asynchronous mode
1b = Synchronous mode
7-6
UCSSELx
RW
3h
eUSCI clock source select. These bits select the BRCLK source clock.
00b = UCxCLK in slave mode. Don't use in master mode.
01b = ACLK in master mode. Don't use in slave mode.
10b = SMCLK in master mode. Don't use in slave mode.
11b = SMCLK in master mode. Don't use in slave mode.
5-2
Reserved
R
0h
Reserved
1
UCSTEM
RW
0h
STE mode select in master mode. This byte is ignored in slave or 3-wire mode.
0b = STE pin is used to prevent conflicts with other masters
1b = STE pin is used to generate the enable signal for a 4-wire slave
0
UCSWRST
RW
1h
Software reset enable
0b = Disabled. eUSCI reset released for operation.
1b = Enabled. eUSCI logic held in reset state.