PXR40RM Datasheet, PDF (900/1434 Pages) Freescale Semiconductor, Inc – PXR40 Microcontroller

Deserial Serial Peripheral Interface (DSPI)
25.4.4.4 DSI Deserialization
When all bits in a DSI frame have been shifted in, the frame is copied to the DSPI DSI Deserialization
Data Register (DSPI_DDR). This register presents the deserialized data as Parallel Output signal values.
The DSPI_DDR is memory mapped to allow host software to read the deserialized data directly.
Figure 25-21 shows the DSI Deserialization logic.
Control
Logic
Slave Bus Interface
SIN
01
N-1
N
Shift Register
N
Parallel
Outputs
DSI Deserialization
Data Register
In TSB configuration the number of bits N = 32, for non TSB it values 16.
Figure 25-21. DSI Deserialization Diagram
25.4.4.5 DSI Transfer Initiation Control
Data transfers for a Master DSPI in DSI configuration are initiated by a condition. The transfer initiation
conditions are selected by the TRRE and CID bits in the DSPI_DSICR. Table 25-27 lists the four transfer
initiation conditions.
Table 25-27. DSI Data Transfer Initiation Control
DSPI_DSICR Bits
TRRE
CID
0
0
0
1
1
0
1
1
Transfer Initiation Control
Continuous
Change in Data
Triggered
Triggered or Change in Data
25.4.4.5.1 Continuous Control
For Continuous Control the initiation of a transfer is based on the baud rate at which data is transferred
between the DSPI and the external device. The baud rate is set in the DSPI_CTAR register selected by the
DSICTAS field in the DSPI_DSICR. A new DSI frame shifts out when the previous transfer cycle has
completed and the Delay after Transfer (t_DT) has elapsed.
25.4.4.5.2 Change In Data Control
For Change in Data Control a transfer is initiated when the data to be serialized has changed since the
transfer of the last DSI frame. A copy of the previously transferred DSI data is stored in the
DSPI_COMPR. When the data in the DSPI_SDR or the DSPI_ASDR is different from the data in the
DSPI_COMPR a new DSI frame is transmitted. The TXSS bit in the DSPI_DSICR selects which register
25-40
PXR40 Microcontroller Reference Manual, Rev. 1
Freescale Semiconductor