Deserial Serial Peripheral Interface (DSPI)MPC5644A Microcontroller Reference Manual, Rev. 6Freescale Semiconductor 132130.9.12 Continuous peripheral chip selectFor peripherals that must remain selected between sequential serial transfers, the DSPI provides the optionof having the PCS signals asserted between transfers. For SPI transfers, the CONT bit in the SPI commandfields selects the continuous PCS feature. For DSI and CSI transfers, the DCONT bit in the DSPI_DSICRselects the continuous PCS feature.30.9.13 Peripheral chip select expansion and deglitchingThe DSPI supports up to 256 Peripheral Chip Select Signals with the use of an external demultiplexer. Upto 128 Peripheral Chip Select Signals can be used if deglitching is desired. The PCSS signal provides theappropriate timing to enable and disable the demultiplexer for the DSPI_x_PCS[0:7] signals.Figure 30-54 shows how an external 8-to-256 demultiplexer (on-board decoder) can be connected to theDSPI.Figure 30-54. DSPI PCS expansion and deglitching30.9.14 DMA and interrupt conditionsThe DSPI has six conditions that can generate interrupt requests and two conditions that can generate bothinterrupt or DMA requests. Table 30-40 lists the conditions. The ‘x’ in the request type columns indicateswhich signals are connected on the MPC5644A.Table 30-40. DSPI interrupt and DMA request conditionsCondition Flag Request typeInterrupt DMAEnd of queue reached EOQF xTX FIFO is not full TFFF x xTransfer of current frame complete TCF xAttempt to transmit with an empty Transmit FIFO TFUF xRX FIFO is not empty RFDF x xFrame received while Receive FIFO is full RFOF xDSPIPCS0-PCS7PCSSPCS0PCS1PCS2568
