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Deserial Serial Peripheral Interface (DSPI)
MPC5644A Microcontroller Reference Manual, Rev. 6
1256
Freescale Semiconductor
30.6
Modes of operation
The DSPI has four modes of operation that can be divided into two categories: module-specific modes and
an MCU-specific mode. Master Mode, Slave Mode and Module Disable Mode are the module-specific
modes, and Debug Mode is the MCU-specific mode.
The module-specific modes are entered by host software writing to a register bit. The MCU-specific mode
is selected by a signal external to the DSPI. The MCU-specific mode is a mode that MPC5644A may enter
in parallel to the DSPI being in one of its module-specific modes.
30.6.1
Master mode
Master Mode allows the DSPI to initiate and control serial communication. In this mode the SCK,
DSPI_x_PCS and SOUT signals are controlled by the DSPI and configured as outputs.
30.6.2
Slave mode
Slave Mode allows the DSPI to communicate with SPI/DSI bus masters. In this mode the DSPI responds
to externally controlled serial transfers. The DSPI cannot initiate serial transfers in Slave Mode.
30.6.3
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 bit DSPI_MCR[MDIS] is set.
30.6.4
Debug mode
Debug Mode is used for system development and debugging. If the MPC5644AMCU enters Debug Mode
while bit DSPI_MCR[FRZ] is set, the DSPI halts operation on the next frame boundary. If the MPC5644A
enters Debug Mode while the FRZ bit is negated, the DSPI behavior is unaffected and remains dictated by
the module-specific mode and configuration of the DSPI.
Table 30-1. DSPI channel frequency support
System clock
(MHz)
DSPI use
mode
Max. usable
frequency (MHz)
Notes
150
LVDS
37.5
Use sysclock /4 divide ratio
Non-LVDS
18.75
Use sysclock /8 divide ratio
120
LVDS
40
Use sysclock /3 divide ratio. Gives 33/66 duty cycle. Use DSPI
configuration DBR = 0b1 (double baud rate), BR = 0b0000
(scaler value 2) and PBR = 0b01 (prescaler value 3).
Non-LVDS
20
Use sysclock /6 divide ratio
80
LVDS
40
Use sysclock /2 divide ratio
Non-LVDS
20
Use sysclock /4 divide ratio
Содержание MPC5644A
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