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TLC2574 Mode 11 operation (REPEAT SWEEP)

Dmitry Reyder
Prodigy 10 points
Other Parts Discussed in Thread: TLC2574

Hello,

I am trying to use the TLC2574 in the REPEAT SWEEP mode using CS as the trigger and the 00-11-22-33 conversion sequence. The data sheet suggests that to begin conversion of a channel, a SELECT command must be sent per channel.

Questions:

  1. Can a sweep be started by simply pulsing CS low, which would start a chain of 8 sampling/conversion sequences, loading the results into FIFO, all autonomous? or
  2. Does CS has to be pulsed LOW for each conversion in the sweep to occur?, or
  3. Does CS has to be brought LOW and kept LOW for the duration of each conversion in the sweep and then brought high at the end of each conversion?, or
  4. Does CS has to go and stay LOW and the SELECT command has to be sent for each of 8 conversions in the sweep?

The data sheet suggest (4), but I am hoping that (1) is true.

  • 0
    TI__Guru**** 174226 points

    Hi Dmitry,

    For the repeat sweep mode in the TLC2574 to work properly using /CS as the trigger, you are actually looking at (2) above with the inclusion of a 'select' command - for instance, you can simply write 0x0000.  The conversion trigger has to toggle for each conversion in the sequence.  Take a look at Figure 18 on page 30 of the datasheet.  Compare that to Figure 19 on page 31.  /CS can be held low if you are using the /CSTART input to initiate the conversions. 

    The other difference between these two figures is that Figure 31 uses the Frame Sync input to retrieve the data.  In either case, during data retrieval, something has to toggle.  If FS is held high, /CS must toggle with the READ FIFO command to retrieve data.