Write only expansion register

Date: 2002-05-06 07:00:09

  • Next message: David Wood: "Re: Write only expansion register"
    Hi all,
    I'm experimenting with the concept of a wiring a write only register when
    the circuit board doesn't have access to the R/W signal (as with for example
    many CBM carts, or a single sided PCB).
    My thinking is that with the appropriate IO select and Phi2 Clock it should
    be possible to get the latch (eg 74175) to accept the data. Logically
    NOR(NOT /IO2 OR CLOCK) for active low data.
    Something like a 7400, 7402 or 74139 chip could decode this logic so that
    data available is latched at the negative edge of the clock.
    Can someone verify if this would be so?
    - Nick
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