Deserial Serial Peripheral Interface (DSPI)
Freescale Semiconductor
25-35
PXR40 Microcontroller Reference Manual, Rev. 1
Figure 25-19. DSPI Start and Stop State Diagram
State transitions from RUNNING to STOPPED occur on the next frame boundary if a transfer is in
progress, or on the next system clock cycle if no transfers are in progress.
25.4.3
Serial Peripheral Interface (SPI) Configuration
The SPI Configuration transfers data serially using a shift register and a selection of programmable
transfer attributes. The DSPI is in SPI Configuration when the DCONF field in the DSPI_MCR is 0b00.
The SPI frames can be from four to sixteen bits long. The data to be transmitted can come from queues
stored in RAM external to the DSPI. Host software or a DMA Controller can transfer the SPI data from
the queues to a First-In First-Out (FIFO) buffer. The received data is stored in entries in the Receive FIFO
(RX FIFO) buffer. Host software or a DMA Controller transfer the received data from the RX FIFO to
memory external to the DSPI. The FIFO buffer operations are described in
Section 25.4.3.4, Transmit First
In First Out (TX FIFO) Buffering Mechanism
Section 25.4.3.5, Receive First In First Out (RX FIFO)
. The interrupt and DMA request conditions are described in
.
The SPI Configuration supports two block-specific modes; Master Mode and Slave Mode. The FIFO
operations are similar for the Master Mode and Slave Mode. The main difference is that in Master Mode
the DSPI initiates and controls the transfer according to the fields in the SPI command field of the TX FIFO
Table 25-26. State Transitions for Start and Stop of DSPI Transfers
Transition #
Current State
Next State
Description
0
RESET
STOPPED
Generic power-on-reset transition
1
STOPPED
RUNNING
The DSPI is started (DSPI transitions to RUNNING) when all of the
following conditions are true:
• EOQF bit is clear
• Debug mode is unselected or the FRZ bit is clear
• HALT bit is clear
2
RUNNING
STOPPED
The DSPI stops (transitions from RUNNING to STOPPED) after
the current frame for any one of the following conditions:
• EOQF bit is set
• Debug mode is selected and the FRZ bit is set
• HALT bit is set
RESET
STOPPED
RUNNING
Power on
TXRXS=0
TXRXS=1
reset
2
1
0
Summary of Contents for PXR4030
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