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Why is PINGETZ/RDPIN/whatever not an implicit PINACK? — Parallax Forums

Why is PINGETZ/RDPIN/whatever not an implicit PINACK?

SeairthSeairth Posts: 2,474
in Propeller 2
I can understand needing a separate ACK instruction for when you don't need to read from the pin (e.g. serial tx). But, is there a reason you would not want to ACK a pin when you read it?

Comments

  • ozpropdevozpropdev Posts: 2,793
    Maybe because multiple cogs can all do a PINGETZ (RDPIN) from any smartpin even if they didn't configure it in the first place.
  • evanhevanh Posts: 16,240
    edited 2016-05-13 14:08
    Multiple Cogs, that aren't synchronised, reading one Smartpin would have some messy gotchas I'd think. On that note, it would make quite good sense for a RDPIN to reset the IN signal.
  • ozpropdevozpropdev Posts: 2,793
    From another thread "Shared Smartpins" Chip said
    All cogs can simultaneously do PINGETZ on the same pin, but PINSETx/PINACK to the same pin cannot be from multiple cogs at once
  • jmgjmg Posts: 15,188
    Seairth wrote: »
    I can understand needing a separate ACK instruction for when you don't need to read from the pin (e.g. serial tx). But, is there a reason you would not want to ACK a pin when you read it?

    I think this could vary with MODE.

    For simple data-flow, as in the new DAC-Path, it makes sense to ACK-on-Read.

    However, with hardware pin actions, there is a limited signaling set between COG and PIN, and some means to separately READ and Re-Arm could be needed with HW Pin Cell use.

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