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AD9858 writing undocumented parallel registers

Category: Datasheet/Specs
Product Number: AD9858

Hello,

some parallel registers are specified as "reserved" in the AD9858 datasheet, but others (0x24-0x3f) are not documented. Is it allowed to write to these undocumented registers? The way how we interface the chip to our bus system would require a write (strobe the WR pin of the parallel interface) to change state of other unrelated chips, so it would be useful if we could just write to undocumented registers. Is this allowed and will simply be ignored or is the behaviour of the chip unspecified for such writes?

Thanks

  • Hi,

    Yes, you are allowed to write to those undocumented registers. These registers will simply be ignored as they are not used by the chip. It is only important that the Reserved registers should not be written and be left on their default values.

    Best regards,

    Mark

  • Hi,

    thanks for the answer. I do not plan to write the reserved registers, but i noticed that for parallel reg. 0x22 the datasheet says the default is 0xFE and to leave it at 0xFF, not sure if that is a typo since the two values specified are different. Just wanted to mention it in case someone else is wiriting to it for whatever reason.

    Best,
    Gregor