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MPC563XM Reference Manual, Rev. 1
1182
Freescale Semiconductor
Preliminary—Subject to Change Without Notice
26.5.3.5.2
Draining the RX FIFO
Host software or other intelligent blocks can remove (pop) entries from the RX FIFO by reading the DSPI
POP RX FIFO Register (DSPI_POPR). A read of the DSPI_POPR decrements the RX FIFO Counter by
one. Attempts to pop data from an empty RX FIFO are ignored, the RX FIFO Counter remains unchanged.
The data returned from reading an empty RX FIFO is undetermined.
When the RX FIFO is not empty, the RX FIFO Drain Flag (RFDF) in the DSPI_SR is set. The RFDF bit
is cleared when the RX_FIFO is empty and the DMA controller indicates that a read from DSPI_POPR is
complete or by host software writing a ‘1’ to the RFDF.
26.5.4
Deserial Serial Interface (DSI) Configuration
The DSI Configuration supports pin count reduction by serializing Parallel Input signals or register bits
and shifting them out in a SPI-like protocol. The timing and transfer protocol is described in
Section 26.5.7, “Transfer Formats
.” The received serial frames are converted to a parallel form
(deserialized) and placed on the Parallel Output signals or in a register. The various features of the DSI
Configuration are set in DSPI DSI Configuration Register (DSPI_DSICR). The DSPI is in DSI
Configuration when the DCONF field in the DSPI_MCR is 0b01.
The DSI frames can be from four to sixteen bits long, but four to 32 bits can be used in the TSB
configuration (see
Section 26.5.9, “Timed Serial Bus (TSB)
” for detailed information). With Multiple
Transfer Operation (MTO) the DSPI supports serial chaining of DSPI blocks within an SoC to create DSI
frames consisting of concatenated bits from multiple DSPIs. The DSPI also supports parallel chaining
allowing several DSPIs and off-chip SPI devices to share the same Serial Communications Clock (SCK)
and Peripheral Chip Select (PCS) signals. See
Section 26.5.4.6, “Multiple Transfer Operation (MTO)
details on the serial and parallel chaining support.
26.5.4.1
DSI Master Mode
In DSI Master Mode the DSPI initiates and controls the DSI transfers. The DSI Master has four different
conditions that can initiate a transfer:
•
Continuous
•
Change in data
•
Trigger signal
•
Trigger signal combined with a change in data
The four transfer initiation conditions are described in
Section 26.5.4.5, “DSI Transfer Initiation Control
Transfer attributes are set during initialization. The DSICTAS field in the DSPI_DSICR determines which
of the DSPI_CTAR registers will control the transfer attributes.
26.5.4.2
Slave Mode
In DSI Slave Mode the DSPI responds to transfers initiated by a SPI or DSI bus master. In this mode the
DSPI does not initiate DSI transfers. Certain transfer attributes such as clock polarity and phase must be
set for successful communication with a DSI master. The DSI Slave Mode Transfer attributes are set in the
DSPI_CTAR1.