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DMA Serial Peripheral Interface (DSPI)
Freescale Semiconductor
31-31
NOTE
For correct operation of the modified transfer format, thoroughly analyze
the SPI link timing budget.
The master and the slave place data on the DSPI_SOUT pins at the assertion of the DSPI_PCS
n
signal.
After the PCS to SCK delay has elapsed, the first DSPI_SCK edge is generated. The slave samples the
master DSPI_SOUT signal on every odd numbered DSPI_SCK edge. The slave also places new data on
the slave DSPI_SOUT on every odd numbered clock edge.
The master places its second data bit on the DSPI_SOUT line one system clock after odd numbered
SDSPI_CK edge. Writing to the DSPI_MCR[SMPL_PT] field selects the point where the master samples
the slave DSPI_SOUT.
lists the number of system clock cycles between the active edge of
DSPI_SCK and the master sample point for different values of the SMPL_PT bit field. The master sample
point can be delayed by one or two system clock cycles.
shows the modified transfer format for CPHA is cleared. Only the condition where CPOL is
cleared is illustrated. The delayed master sample points are indicated with a lighter shaded arrow.
Figure 31-17. DSPI Modified Transfer Format (MTFE = 1, CPHA = 0, Fsck = Fsys/4)
Table 31-19. Delayed Master Sample Point
SMPL_PT
Number of System Clock Cycles between
Odd-numbered Edge of SCK and Sampling of SIN
00
0
01
1
10
2
11
Reserved
t
CSC
= PCS to SCK delay.
t
ASC
= After SCK delay.
System Clock
1
2
3
4
5
6
DSPI_PCSn
t
ASC
DSPI_SCK
Master Sample
Slave DSPI_SOUT
Master DSPI_SOUT
System Clock
System Clock
Slave Sample
t
CSC
Содержание MCF54455
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