Freescale Semiconductor MPC5565, Reference Manual

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Deserial Serial Peripheral Interface (DSPI)
MPC5565 Microcontroller Reference Manual, Rev. 1.0
19-48 Freescale Semiconductor
19.4.4.7.2 Parallel Chaining
Parallel chaining allows the PCS x and SCK x signals from a master DSPI to be shared by internal slave
DSPIs and external slave SPI devices. Signal sharing reduces DSPI pin utilization. An example of a
parallel chain is shown in
Figure 19-25 .
Figure 19-25. Example of Parallel Chaining of DSPIs
In the parallel chaining example, the SOUT x and SIN x of the DSPIs connect to separate external SPI
devices. All internal and external SPI modules share PCS x and SCK x signals. DSPI B controls and initiates
all transfers, but the DSPI slaves each have a trigger output signal MTRIG that indicates to DSPI B that a
trigger condition has occurred in the DSPI slaves.
When the slave DSPI has a change in data to be serialized, it asserts the MTRIG signal that propagates to
DSPI B which initiates the transfer.
The MTOCNT field in the DSPI x _DSICR must be written with the number of bits to be transferred. In
parallel chaining the number written to MTOCNT must match the FMSZ field in the selected
DSPI x _CTAR.
SOUT
HT
SCK
SIN
MTRIG
SS
MCU
DSPI B
SOUT
HT
SCK
SIN
PCS[0]
SINB
PCSB[0]
SCK
B
SOUTB SINC
(master)
DSPI C
(slave)
SOUT
SCK
SIN
MTRIG
SS
DSPI D
(slave)
SOUTC SI
ND
SOUTD
SCK SS
SIN
Slave device
SPI
SOUT
SCK SS
SIN
Slave device
SPI
SOUT
SCK SS
SIN
Slave device
SPI
SOUT