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SPORT Multichannel issue

Question asked by ChristianH on Jul 30, 2015
Latest reply on Aug 12, 2015 by ChristianH

Hi all,


I've a little issue using the SPORTs in multichannel mode.

Configuration is following:

     ustat1 = (MFD0 | NCH7);

     dm(SPMCTL3) = ustat1;

     ustat1 = 0xFF;

     dm(SP3CS0) = ustat1;

     ustat1 = (SLEN32 | SCHEN_A | SDEN_A | SCHEN_B | SDEN_B | CKRE | LMFS | SPTRAN);

     dm(SPCTL3) = ustat1;

     ustat1 = dm(SPMCTL3);

    bit set ustat1 (MCEA | MCEB);

    dm(SPMCTL3) = ustat1;


So I use the SPORT3 as transmitter with 8 channels, no frame delay, DMA chaining.

I have 96kHz frame clock, 24.576MHz bit and master clock, all supplied from external to the DSP.


If I use this configuration, the data words start ~3 bit clock cycles after falling frame clock edge.

If I remove the LMFS setting (i.e. Slot1 starts with frame clock high instead of low) it works correctly but on rising frame clock edge of course.


Why does it not work with frame start on frame clock low?

Any ideas?