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ADS8557: BUSY Signal

Viktorija Cecil
Genius 17961 points
Part Number: ADS8557

Team,

Question from my customer:

We have a query on what to do with the “BUSY” signal.  Our intention is to start the “ConvStart” for all the A/D devices at the same time (as shown in Figure 38 of the datasheet). 

                BUT we plan to tie the “BUSY” to an interrupt which would trigger Serial data transfer.  Ideally BOTH A/D devices would hold a shared busy signal high and when they are complete, they would release it.  Because the BUSY signal’s polarity  can be changed, I am assuming this output is a “push-pull” and thus we need to OR the two device BUSY signals together?

Thanks

Viktorija

  • 0
    TI__Mastermind 35520 points

    Hi Viktorija,
    The "BUSY" width on devices may have a slightly difference but definitely it meets the specification(maximum conversion time 1.19us for ADS8557). The "BUSY" high means the conversion is ongoing and the conversion data should be read when BUSY is low (the conversion ends). When multiple ADS8557s are designed and their "BUSY" signals are used to trigger the interrupt on MCU/CPU, the longer BUSY signal should be used for triggering, hence an "AND" logic should be used for these "BUSY" signals.
    Thanks.

    Best regards,
    Dale