SPI Protocol: CLKSTP
11-82
Figure 11–54.
SPI Transfer with CLKSTP = 10b
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FSX/SS
D(R/X)/MISO
(from slave)§
D(R/X)/MOSI
(from master)†
CLKX (CLKXP=1)/SCK
CLKX (CLKXP=0)/SCK
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Figure 11–55.
SPI Transfer with CLKSTP = 11b
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B4
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B5
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B1
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FSX/SS
D(R/X)/MISO
(from slave)§
D(R/X)/MOSI
(from master)†
CLKX (CLKXP=1)/SCK
CLKX (CLKXP=0)/SCK
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ
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† If the McBSP is the SPI master (CLKXM = 1), MOSI=DX. If the McBSP is the SPI slave (CLKXM = 0), MOSI = DR.
§ If the McBSP is the SPI master (CLKXM = 1), MISO=DR. If the McBSP is the SPI slave (CLKXM = 0), MISO = DX.
The CLKSTP and CLKXP fields of the serial port control register (SPCR) select
the appropriate clock scheme for a particular SPI interface, as shown in
Table 11–21. The CLKSTP and CLKXP fields in the SPCR determine the fol-
lowing conditions:
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Whether clock stop mode is enabled or not
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In clock stop mode, whether the clock is high or low when stopped
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In clock stop mode, whether the first clock edge occurs at the start of the
first data bit or at the middle of the first data bit
The CLKXP bit selects the edge on which data is transmitted (driven) and
received (sampled), as shown in Table 11–21.