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RM0090: Reference manual - STMicroelectronics

RM0090: Reference manual - STMicroelectronics

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Serial peripheral interface (SPI) <strong>RM0090</strong><br />

MSB justified standard<br />

For this standard, the WS signal is generated at the same time as the first data bit, which is<br />

the MSBit.<br />

Figure 294. MSB Justified 16-bit or 32-bit full-accuracy length with CPOL = 0<br />

CK<br />

WS<br />

SD<br />

MSB LSB MSB<br />

Data are latched on the falling edge of CK (for transmitter) and are read on the rising edge<br />

(for the receiver).<br />

Figure 295. MSB Justified 24-bit frame length with CPOL = 0<br />

CK<br />

WS<br />

SD<br />

Transmission Reception<br />

May be 16-bit, 32-bit<br />

Channel left<br />

Figure 296. MSB Justified 16-bit extended to 32-bit packet frame with CPOL = 0<br />

CK<br />

WS<br />

SD<br />

Transmission<br />

24-bit data<br />

MSB LSB<br />

Reception<br />

Channel left 32-bit<br />

Transmission Reception<br />

16-bit data<br />

MSB LSB<br />

Channel left 32-bit<br />

821/1416 Doc ID 018909 Rev 3<br />

8-bit remaining<br />

0 forced<br />

16-bit remaining<br />

0 forced<br />

Channel right<br />

Channel right<br />

Channel right

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