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SPI interbyte delay on K26/K65

Question asked by Anders Esbensen on Sep 5, 2017
Latest reply on Sep 6, 2017 by EARL GOODRICH


Working on optimizing transfer rates to s SPI flash I have observed quite large inter byte/word delay on the SPI bus.

My system is running 120 MHz system clock and 30 MHz SPI clock, and i am using the standard fsl_dspi_edma driver.


When transmitting multiples bytes via DMA, i see that the transfer of the each 8 data bits take about 266ns as expected, but between bytes i see a delay of  ~100 ns.   Transfer is done with kDSPI_MasterPcsContinuous set.


I was initially using SPI1, and as i was suspecting the delay being related to the missing FIFO on this channel i moved to SPI0 that has 4 level FIFO.  However i see the same timing the channel.


Are there any ways to control interword timing on SPI transfers or is the interbyte delay expected behaviour?