Deserial Serial Peripheral Interface (DSPI)
Freescale Semiconductor
25-39
PXR40 Microcontroller Reference Manual, Rev. 1
•
Trigger signal combined with a change in data
The four transfer initiation conditions are described in
Section 25.4.4.5, 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.
25.4.4.2
DSI 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.
If the CID bit in the DSPI_DSICR is set and the data in the DSPI_COMPR differs from the selected source
of the serialized data, the slave DSPI will assert the MTRIG signal. If the slave’s HT signal is asserted and
the TRRE is set, the slave DSPI asserts MTRIG. These features are included to support chaining of several
DSPI. Details about the MTRIG signal is found in
Section 25.4.4.6, Multiple Transfer Operation (MTO)
.
25.4.4.3
DSI Serialization
In the DSI Configuration from four to sixteen bits can be serialized using two different sources. The TXSS
bit in the DSPI_DSICR selects between the DSPI DSI Serialization Data Register (DSPI_SDR) and the
DSPI DSI Alternate Serialization Data Register (DSPI_ASDR) as the source of the serialized data. The
DSPI_SDR holds the latest Parallel Input signal values which is sampled at every rising edge of the system
clock. The DSPI_ASDR register is written by host software and used as an alternate source of serialized
data.
A copy of the last 32-bit DSI frame shifted out of the Shift Register is stored in the DSPI DSI Transmit
Comparison Register (DSPI_COMPR). This register provides added visibility for debugging and it serves
as a reference for transfer initiation control.
shows the DSI Serialization logic.
Figure 25-20. DSI Serialization Diagram
DSI Config.
SOUT
Shift Register
HT
0 1
15
Clock
Logic
SCK
TXSS
0
1
Register
Control
Logic
DSI Transmit
Comparison Register
PCS
DSI Serialization
Data Register
32
32
32
DSPI Alternate
Serialization Data Register
Parallel
Inputs
32
0
1
16
Slave Bus Interface
Summary of Contents for PXR4030
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