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DAC7811: DAC7811 : SYNC Interrupt (Stand-alone Mode)

Steve Claffey
Prodigy 110 points
Part Number: DAC7811

The DAC7811 datasheet refers to the ability to interrupt a command by de-asserting SYNC/ before the 16th falling edge of SCLK.  Do I explicitly need to issue a  "Daisy-Chain Disable" command before the SYNC Interrupt will work correctly?  Is that what is implied by Stand-Alone mode?

7.4.3 SYNC Interrupt (Stand-Alone Mode)
In a normal write sequence, the SYNC line is kept low for at least 16 falling edges of SCLK and the DAC is
updated on the 16th falling edge. However, if SYNC is brought high before the 16th falling edge, this acts as an
interrupt to the write sequence. The shift register is reset and the write sequence is seen as invalid. Neither an
update of the DAC register contents nor a change in the operating mode occurs.

Thanks in advance for any assistance.

  • 0
    TI__Mastermind 46290 points

    Hi Steve,

    Excellent question. My belief concerning why the document phrases things as it does is as follows...

    In stand alone mode serial input data is latched on the 16th falling edge. In daisy chain mode serial input data inherently cannot be latched on the 16th falling edge since we must apply 16n clocks for data to propagate through the entire chain, therefore in daisy-chain mode the design must use the rising edge of SYNC as the latching mechanism.

    In either stand alone or daisy chain operation I believe that the SYNC interrupt will function correctly and disregard incomplete input frames when less than 16 total clocks have been issued. This is not to imply that frames are disregarded if 16n frames are not issued in daisy chain mode as the devices would have no means of knowing whether the data was intended for "them" or the next device in the chain.

    I hope this makes sense and answers your question. Thanks.