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OrCad Capture power pins

Discussion in 'CAD' started by Malcolm Reeves, Feb 2, 2005.

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  1. Hi,

    I can't seem to find a good way of having logic gates on different
    rails.

    My options seem to be:

    Edit part to change power name for each part.
    Make power pins passive and thus visible on all gates and connect.

    Both seem naff to me. Is there another way?


    --

    Malcolm

    Malcolm Reeves BSc CEng MIEE MIRSE, Full Circuit Ltd, Chippenham, UK
    (, or ).
    Design Service for Analogue/Digital H/W & S/W Railway Signalling and Power
    electronics. More details plus freeware, Win95/98 DUN and Pspice tips, see:

    http://www.fullcircuit.com or http://www.fullcircuit.co.uk

    NEW - www.CharteredConsultant.co.uk - The Consultant A-List
     
  2. Jim Thompson

    Jim Thompson Guest

    I'm heading to the airport, to Pittsburgh for a few days. Will show a
    trick when I get back.

    ...Jim Thompson
     
  3. Ken Smith

    Ken Smith Guest

    In the DOS Orcad, you could make passive pins that appeared only on one
    part in the package. Such schematics import into capture ok so I assume
    you can do the same in capture, but this may not be true. I've discovered
    that some things that are quick and easy to do in the DOS version don't
    seem posible in the windows software.
     
  4. Geo

    Geo Guest

    Rubbish :)
    Hidden power pins are a complete PITA to a service tech. When you come to
    service the product, the circuit MUST show which supply each chip is connected
    to. And preferably on the chip not in some hand-typed table...
    Geo
     
  5. |> Hi,
    |>
    |> I can't seem to find a good way of having logic gates on different
    |> rails.
    |>
    |> My options seem to be:
    |>
    |> Edit part to change power name for each part.
    |> Make power pins passive and thus visible on all gates and connect.
    |>
    |> Both seem naff to me. Is there another way?

    Well, I don't think you would want the first option. That would hide
    the power connections so that you would not be able to see what rails
    they are connected to.

    In Capture, you can select the part, and then right click and select
    "Edit Properties". At the bottom of the dialog box, check "Power Pins
    Visible". Then you can wire the pins to whatever rails you want. I
    THINK (check this) that this will have the desired effect of
    overriding the power name on the pin. Alternatively, it might cause
    you to interconnect all your power buses, but I don't think it does
    that.

    The bad thing about this is that many of the Orcad parts have zero
    length pins for the power pins, and the pins may not be located on the
    part body where you would like to see them. I suppose that this is
    because they forgot that someone might actually want to make these
    pins visible. The work around, of course, is to make your own library
    of parts on which you want sane power pins. This is what I usually do.

    --
    NOTE: to reply, remove all punctuation from email name field

    Ned Forrester 508-289-2226
    Applied Ocean Physics and Engineering Dept.
    Oceanographic Systems Lab http://adcp.whoi.edu/
    Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA
     
  6. Hi Malcolm,
    You are using Capture, right? If so, you can just make the power pins
    visible, and attach them to the different rails. That makes it pretty
    apparent.

    Of course, if you are using PSpice, only some of the parts have the
    ability to use different power supply rails, spec. only the CMOS based
    parts usually have the option...
     
  7. Thanks to all for their suggestions but let me address this point.

    I would agree that hidden power pins are a pain, but then so is power
    pins on all 6 gates. The best method I have seen is where a part has
    6 gates and a power block. That way you can put the power block on a
    decoupling sheet. The information is all there but the power pins
    don't clutter up the logic as normally you don't care about the rails
    (i.e. if they are all VCC).

    In my circuit I have opted for editing the gate to two different
    parts. One with the label VCCa connecting to VCCa and one VCCb. That
    way I can pick the appropriate part for the right rail and annotate
    won't assign the wrong gate to the wrong package. The labels are
    shown in on each part of course.

    The alternative of power pins visible I'd have to do for all gates to
    ensure they all packaged right. Since I only have two ICs my method
    seems more tidy.


    --

    Malcolm

    Malcolm Reeves BSc CEng MIEE MIRSE, Full Circuit Ltd, Chippenham, UK
    (, or ).
    Design Service for Analogue/Digital H/W & S/W Railway Signalling and Power
    electronics. More details plus freeware, Win95/98 DUN and Pspice tips, see:

    http://www.fullcircuit.com or http://www.fullcircuit.co.uk

    NEW - www.CharteredConsultant.co.uk - The Consultant A-List
     
  8. Jim Thompson

    Jim Thompson Guest

    Malcolm, Here is the way I do it with my individual logic parts
    within I/Cs...

    Mylib.slb : INVERTER

    Pin Data
    U? VP
    X Y E R C# Name invert_a

    VN 0 20 i 1 A
    50 20 o 2 Y
    30 0 x 3 VP
    30 40 x 4 VN
    Symbol Data:

    Description = Inverter
    Type = p
    Bbox = (0 0) (50 40)
    Origin = (0 20)

    Attributes

    PART = INVERTER
    REFDES = U?
    TEMPLATE = X^@REFDES %A %Y ?GLOPWR|[email protected] [email protected]|%VP %VN|@MODEL
    MODEL = invert_a
    GLOPWR =
    VPLUS = PWRP
    VNEG = PWRN

    This is, of course, with Schematics, not Capture, which you seem to
    have switched to ;-)

    ...Jim Thompson
     
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