On 02:11 PM 9/04/2001 -0700, Abd ul-Rahman Lomax said:
>At 07:27 PM 4/9/01 +0100, Terry Harris wrote:
>
>>The Cadence schematic stuff I have used a little works like this. Every bus
>>entry/exit has a numeric tag to identify which member of the bus you are
>>connecting. Busses can also be split and merged again with numeric range
>>tags. Symbols can even have bus 'pins' a whole 48 bit data bus on a
>>component can be connected directly to a bus (obviously no pin number
>>information shown).
>
>Ah, hidden pins! That's really what those are. (Though the Cadence
>implementation might well be more sophisticated, like being able to
>connect DATA1-8, hidden, with the bus D[0..7]. Obviously such a scheme
>could get really hairy if the signals were not simply assigned in
>numerical sequence)
>You can do this now by hiding the pins, with the name of the pin being the
>name of the net you want assigned to the pin. Of course, the connectivity
>would be global. It might be nice if there were a hidden pin attribute
>that made a net with sheet-only scope, which could be useful for this as
>well as the hidden power pin problem, where VCC is +5V on one page and
>+3.3V on another.
Oh no! You are surely not suggesting that someone should hide a bus and use
hidden pin connectivity are you? I can't see how what Terry described is
anything to do with a hidden pins.
Bus Pin:
1) You see the bus pin
2) you have control of connectivity (not global)
3) there is a bus wire showing the connections on the schematic.
How does this compare with hidden pins where:
1) you can see the pin
2) net is global always
3) you can't see where the connection is going to.
(I'm glad you go on to say this would
>I'm not entirely thrilled by the idea of hiding pin assignments. It's
>great for making a nice, neat, compact, readable, schematic, but the
>technicians will be sticking pins in voodoo dolls with a picture of your
>face taped on its head. The last thing one wants to do when sweating a
>deadline, and one needs to know what pin net A5 is on, is to have to look
>it up somewhere else than the schematic sheet with the part on it.
>
>But if there were a schematic with many instances of a part, it might well
>be useful to have a small version of a part with such hidden pins. One
>could then have the full symbol in one place, showing all the pins, and
>then the abbreviated version for other instances. It's worth looking into.
Personally, I disagree that it is worth looking into - I think it can only
take Protel further from improving the visibility of the design.
Ian Wilson
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