Deserial Serial Peripheral Interface (DSPI)MPC5644A Microcontroller Reference Manual, Rev. 61290 Freescale Semiconductor30.9 Functional descriptionThe Deserial Serial Peripheral Interface (DSPI) module supports full-duplex, synchronous serialcommunications between MCUs and peripheral devices. The DSPI can also be used to reduce the numberof pins required for I/O by serializing and deserializing up to 32 Parallel Input/Output signals. Allcommunications are done with SPI-like protocol.The DSPI has three configurations:• SPI configuration in which the DSPI operates as a basic SPI or a queued SPI.• DSI configuration in which the DSPI serializes and deserializes Parallel Input/Output signals orbits from memory mapped register.• CSI configuration in which the DSPI combines the functionality of the SPI and DSI configurations.Field DSPI_MCR[DCONF] determines the DSPI configuration. See Table 30-4 for the DSPIconfiguration values.Registers DSPI_CTAR0 – DSPI_CTAR7 hold clock and transfer attributes. The SPI configuration allowsto select which DSPI_CTAR to use on a frame by frame basis by setting a field in the SPI command. TheDSI configuration statically selects which DSPI_CTAR to use. In CSI configuration priority logicdetermines if SPI data or DSI data is transferred and dictates what DSPI_CTAR is used for the datatransfer. See Section 30.8.2.4, DSPI Clock and Transfer Attributes Registers 0–7(DSPI_CTAR0–DSPI_CTAR7), for information on the fields of the DSPI_CTAR registers.Typical master to slave connections are shown in Figure 30-30. When a data transfer operation isperformed, data is serially shifted a predetermined number of bit positions. Because the modules arelinked, data is exchanged between the master and the slave. The data that was in the master shift registeris now in the shift register of the slave, and vice versa. At the end of a transfer, bit DSPI_SR[TCF] is setto indicate a completed transfer.Table 30-31. DSPI_DIPR Field DescriptionsField DescriptionDP[]Data Polarity. The DP bits define what value of the received deserialization data sets theDSPI_SR[DDIF] bit.0 if received bit is 0 the DSPI_SR[DDIF] bit is set.1 if received bit is 1 the DSPI_SR[DDIF] bit is set.
