9 Replies Latest reply on Apr 13, 2011 3:27 AM by udayan.umapathi

    Why does SPI stall between bytes?

    louis.koziarz

      Thanks to Uday I've got some SPI transmission working, but I'm seeing a very strange problem with the transmission speed on SPI.

         

      My device is a CY8C3866-ES3.  I'm using a SPIM Mode 0 @ 2.5 MBit, tx/rx buffer set to 96 bytes.  I fill TX with 80 bytes using SPIM_PutArray and then watch the transmission using my scope.

         

      What I see is 8 bits getting clocked out in about 3.2 microseconds, then a 17 uSec gap before the next byte starts to transmit. 

         

      I have two interrupts enabled besides the default: IRQ on Tx FIFO empty and IRQ on Rx FIFO full.

         

      What could be stalling the SPI hardware to take this long before sending another byte?  This effectively is limiting my SPI transmission to under 1Mbit when I should be going 2-3 times faster.

         

      Thanks,

         

      Louis