UM10139

Philips SemiconductorsVolume 1UM10139Chapter 13: SSPdevice between each data transfer to enable the serial peripheral data write. Oncompletion of the continuous transfer, the SSEL pin is returned to its idle state one SCKperiod after the last bit has been captured.13.3.7 SPI format with CPOL = 1,CPHA = 1The transfer signal sequence for SPI format with CPOL = 1, CPHA = 1 is shown inFigure 46, which covers both single and continuous transfers.SCKSSELMOSIMSBLSBMISO Q MSBLSBQ4 to 16 bitsa) Motorola SPI frame format (single transfer) with CPOL=1 and CPHA=1Fig 46. SPI frame format with CPOL = 1 and CPHA = 1In this configuration, during idle periods:• The CLK signal is forced HIGH• SSEL is forced HIGH• The transmit MOSI/MISO pad is in high impedanceIf the SSP is enabled and there is valid data within the transmit FIFO, the start oftransmission is signified by the SSEL master signal being driven LOW. Master’s MOSI isenabled. After a further one half SCK period, both master and slave data are enabled ontotheir respective transmission lines. At the same time, the SCK is enabled with a fallingedge transition. Data is then captured on the rising edges and propagated on the fallingedges of the SCK signal.After all bits have been transferred, in the case of a single word transmission, the SSELline is returned to its idle HIGH state one SCK period after the last bit has been captured.For continuous back-to-back transmissions, the SSEL pins remains in its active LOWstate, until the final bit of the last word has been captured, and then returns to its idle stateas described above. In general, for continuous back-to-back transfers the SSEL pin is heldLOW between successive data words and termination is the same as that of the singleword transfer.13.3.8 Semiconductor Microwire frame formatFigure 47 shows the Microwire frame format for a single frame. Figure 44 shows the sameformat when back-to-back frames are transmitted.© Koninklijke Philips Electronics N.V. 2005. All rights reserved.User manual Rev. 01 — 15 August 2005 186