NXP Semiconductors MPC5644A, Reference Manual, Page: 1300 / 1735

Deserial Serial Peripheral Interface (DSPI)
MPC5644A Microcontroller Reference Manual, Rev. 6
1300 Freescale Semiconductor
Figure 30-34. DSPI serial chaining example
The SOUT of DSPI_B is connected to the SIN of DSPI_C, the SOUT of DSPI_C is connected to the SIN
of DSPI_D and the SOUT of the DSPI_D is connected to the SIN of the external SPI slave. The SOUT of
the external SPI slave is connected to the SIN of DSPI_B.
DSPI_B controls and initiates all transfers, but the slave DSPIs use the trigger output signal MTRIG to
indicate to DSPI_B that a trigger condition has occurred. When an on-chip DSPI slave has a change in data
to be serialized it can assert the MTRIG signal to the DSPI master which initiates the transfer. The DSPI
slaves also propagate trigger signals from other slaves to the DSPI master.
Field DSPI_DSICR[MTOCNT] in DSPI_B must be written with the total number of bits to be transferred.
Field DSPI_DSICR[MTOCNT] must equal the sum of all FMSZ fields in the selected DSPI_CTAR
registers for DSPI_B and all on-chip DSPI slaves. For example, if one 16-bit DSI frame is created by
concatenating 8 bits from DSPI_B and 4 bits from DSPI_C and DSPI_D each, then DSPI_B’s frame size
must be set to 8, and the DSPI slaves’ frame size must be set to 4 each. Field DSPI_DSICR[MTOCNT] in
DSPI_B must be set to 16.
30.9.3.8 IMUX/SIU support for serial and parallel chaining
To support MTO, each DSPI in the MPC5644A has multiplexers on the SIN, SS, SCK, and HT inputs. The
Internal Multiplexers (IMUX) reside in the SIU module on the MPC5644A.
SOUT
SOUT
SIN
SIN
PCS[x] SS SCK
SCK
DSPI_B Master
DSPI_C Slave
SS SCK
SIN
SOUT
External SPI Slave Device
DEVICE
MTRIG
HT
SOUT
SIN
SS
SCK
DSPI_D Slave
MTRIG HT
SOUT_
D
SCK_B
SI
N_B
PCS_B[0
]