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Chapter 20 Deserial Serial Peripheral Interface (DSPI)
MPC5602P Microcontroller Reference Manual, Rev. 4
462
Freescale Semiconductor
20.8.1.2
Slave mode
In slave mode the DSPI responds to transfers initiated by an SPI master. The DSPI operates as bus slave
when the MSTR bit in the DSPI
x
_MCR is negated. The DSPI slave is selected by a bus master by having
the slave’s CS0_
x
asserted. In slave mode, the SCK is provided by the bus master. All transfer attributes
are controlled by the bus master, except the clock polarity, clock phase, and the number of bits to transfer.
These must be configured in the DSPI slave for correct communications.
20.8.1.3
Module disable mode
The module disable mode is used for MCU power management. The clock to the non-memory mapped
logic in the DSPI is stopped while in module disable mode. The DSPI enters the module disable mode
when the MDIS bit in DSPI
x
_MCR is set.
Refer to
Section 20.8.8, “Power saving features
for more details on the module disable mode.
20.8.1.4
Debug mode
The debug mode is used for system development and debugging. If the MCU enters debug mode while the
FRZ bit in the DSPI
x
_MCR is set, the DSPI stops all serial transfers and enters a stopped state. If the MCU
enters debug mode while the FRZ bit is cleared, the DSPI behavior is unaffected and remains dictated by
the module-specific mode and configuration of the DSPI. The DSPI enters debug mode when a debug
request is asserted by an external controller.
Refer to
for a state diagram.
20.8.2
Start and stop of DSPI transfers
The DSPI has two operating states: STOPPED and RUNNING. The states are independent of DSPI
configuration. The default state of the DSPI is STOPPED. In the STOPPED state no serial transfers are
initiated in master mode and no transfers are responded to in slave mode. The STOPPED state is also a
safe state for writing the various configuration registers of the DSPI without causing undetermined results.
The TXRXS bit in the DSPI
x
_SR is cleared in this state. In the RUNNING state, serial transfers take place.
The TXRXS bit in the DSPI
x
_SR is set in the RUNNING state.
shows a state diagram of the start and stop mechanism.
Figure 20-13. DSPI start and stop state diagram
The transitions are described in
RUNNING
TXRXS = 1
STOPPED
TXRXS = 0
RESET
Power-on-Reset
0
1
2