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USART Registers: SPI Mode
14-15
USART Peripheral Interface, SPI Mode
UxTCTL, USART Transmit Control Register
76543210
CKPH CKPL SSELx Unused Unused STC TXEPT
rw−0 rw−0 rw−0 rw−0 rw−0 rw−0 rw−0 rw−1
CKPH
Bit 7 Clock phase select. Controls the phase of UCLK.
0 Normal UCLK clocking scheme
1 UCLK is delayed by one half cycle
CKPL
Bit 6 Clock polarity select
0 The inactive level is low; data is output with the rising edge of UCLK;
input data is latched with the falling edge of UCLK.
1 The inactive level is high; data is output with the falling edge of
UCLK; input data is latched with the rising edge of UCLK.
SSELx
Bits
5-4
Source select. These bits select the BRCLK source clock.
00 External UCLK (valid for slave mode only)
01 ACLK (valid for master mode only)
10 SMCLK (valid for master mode only)
11 SMCLK (valid for master mode only)
Unused
Bit 3 Unused
Unused
Bit 2 Unused
STC
Bit 1 Slave transmit control.
0 4-pin SPI mode: STE enabled.
1 3-pin SPI mode: STE disabled.
TXEPT
Bit 0 Transmitter empty flag. The TXEPT flag is not used in slave mode.
0 Transmission active and/or data waiting in UxTXBUF
1 UxTXBUF and TX shift register are empty