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DMA Serial Peripheral Interface (DSPI)
31-22
Freescale Semiconductor
Figure 31-12. 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.
31.4.2
Serial Peripheral Interface (SPI) Configuration
The SPI configuration transfers data serially using a shift register and a selection of programmable transfer
attributes. The SPI frames can be from 4–16 bits long. The data transmitted can come from queues stored
in RAM external to the DSPI. Host software or the eDMA 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 the eDMA controller transfers the received data from the RX FIFO to
memory external to the DSPI. The FIFO buffer operations are described in
,” and
Section 31.4.2.5, “RX FIFO Buffering Mechanism
.
”
The interrupt and DMA
request conditions are described in
Section 31.4.6, “Interrupts/DMA Requests
.
”
The SPI configuration supports two module-specific modes; master mode and slave mode. The FIFO
operations are similar for both modes. In master mode, the DSPI initiates and controls the transfer
according to the SPI command field of the TX FIFO entry. In slave mode, the DSPI only responds to
transfers initiated by a bus master external to the DSPI, and the SPI command field of the TX FIFO entry
is ignored. For information on switching between master and slave modes see
Table 31-12. 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
RUNNING
TXRXS = 1
STOPPED
TXRXS = 0
RESET
Power-on-Reset
0
1
2
Summary of Contents for MCF54455
Page 33: ...xxviii Freescale Semiconductor ...
Page 67: ...Freescale Semiconductor 1 ...
Page 125: ...Freescale Semiconductor 1 ...
Page 145: ...Enhanced Multiply Accumulate Unit EMAC 5 21 Freescale Semiconductor ...
Page 173: ...Cache 6 28 Freescale Semiconductor ...
Page 179: ...Static RAM SRAM 7 6 Freescale Semiconductor ...
Page 207: ...Power Management 9 16 Freescale Semiconductor ...
Page 323: ...Reset Controller Module 13 8 Freescale Semiconductor ...
Page 389: ...Pin Multiplexing and Control 16 44 Freescale Semiconductor ...
Page 575: ...PCI Bus Controller 22 58 Freescale Semiconductor ...
Page 600: ...Advanced Technology Attachment ATA Freescale Semiconductor 23 25 ...
Page 601: ...Freescale Semiconductor 1 ...
Page 842: ...I2 C Interface Freescale Semiconductor 33 16 ...
Page 843: ...Freescale Semiconductor 1 ...
Page 921: ...Revision History A 6 Freescale Semiconductor ...