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NUC126
Aug. 08, 2018
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602
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Rev 1.03
NUC12
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6.16.6
Timing Diagram
The active state of slave selection signal can be defined by setting the SSACTPOL (SPIx_SSCTL[2]).
The SPI clock which is in idle state can be configured as high or low state by setting the CLKPOL
(SPIx_CTL[3]). It also provides the bit length of a transaction word in DWIDTH (SPIx_CTL[12:8]), and
transmitting/receiving data from MSB or LSB first in LSB (SPIx_CTL[13]). User can also select which
edge of SPI clock to transmit/receive data in TXNEG/RXNEG (SPIx_CTL[2:1]). Four SPI timing
diagrams for master/slave operations and the related settings are shown below.
SPIx_CLK
SPIx_MISO
SPIx_MOSI
TX[6]
TX[4]
TX[3]
TX[2]
LSB
TX[0]
RX[6]
RX[4]
RX[2]
LSB
RX[0]
MSB
RX[7]
RX[3]
MSB
TX[7]
SPIx_SS
CLKPOL=0
CLKPOL=1
TX[5]
RX[5]
TX[1]
RX[1]
SSACTPOL=0
SSACTPOL=1
Master Mode: SLVAE=0, LSB=0, DWIDTH=0x08
1. CLKPOL=0, TXNEG=1, RXNEG=0 or
2. CLKPOL=1, TXNEG=0, RXNEG=1
Figure 6.16-22 SPI Timing in Master Mode
SPIx_CLK
SPIx_MISO
SPIx_MOSI
TX[1]
TX[3]
TX[4]
TX[5]
MSB
TX[7]
RX[1]
RX[3]
RX[5]
MSB
RX[7]
LSB
RX[0]
RX[4]
LSB
TX[0]
SPIx_SS
CLKPOL=0
CLKPOL=1
TX[2]
RX[2]
TX[6]
RX[6]
SSACTPOL=0
SSACTPOL=1
Master Mode: SLVAE=0, LSB=1, DWIDTH=0x08
1. CLKPOL=0, TXNEG=0, RXNEG=1 or
2. CLKPOL=1, TXNEG=1, RXNEG=0
Figure 6.16-23 SPI Timing in Master Mode (Alternate Phase of SPIx_CLK)