MPC5553/MPC5554 Microcontroller Reference Manual, Rev. 5
Freescale Semiconductor
20-59
NOTE
For correct operation of the modified transfer format, the user must
thoroughly analyze the SPI link timing budget.
Figure 20-39. DSPI Modified Transfer Format (MTFE = 1, CPHA = 1, Fsck = Fsys/4)
20.4.7.5
Continuous Selection Format
Some peripherals must be deselected between every transfer. Other peripherals must remain selected
between several sequential serial transfers. The continuous selection format provides the flexibility to
handle both cases. The continuous selection format is enabled for the SPI configuration by setting the
CONT bit in the SPI command. Continuous selection is enabled for the DSI configuration by setting the
DCONT bit in the DSPI
x
_DSICR. The behavior of the PCS signals in the two configurations is identical
so only SPI configuration will be described.
When the CONT bit = 0, the DSPI drives the asserted chip select signals to their idle states in between
frames. The idle states of the chip select signals are selected by the PCSIS field in the DSPI
x
_MCR.
shows the timing diagram for two four-bit transfers with CPHA = 1 and CONT = 0.
t
CSC
= PCS to SCK delay.
t
ASC
= After SCK delay.
System Clock
1
2
3
4
5
6
PCS
t
ASC
SCK
Master Sample
Master SOUT
Slave SOUT
Slave Sample
t
CSC
Summary of Contents for MPC5553
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