On 08:46 AM 22/05/2002 +1200, Brendon Slade said:
>It's not just the fact that the pin is hidden.  If the pin's Electrical Type
>is "Power" and the pin is hidden, then it is assumed by Protel that the pin
>is connected to a net of the same name as the Pin Name, whatever that is.
>
>Cheers
>Brendon.


Brendon,

Actually this is not quite true.  Hidden pin connectivity is *not* 
dependent of pin electrical type.  Its normal function would be for use 
with power nets but there it is not restricted to "power" pins.

As I said before, if you are not very experienced with Protel and do not 
*fully* understand the *full* implications of hidden pins you should not be 
using them.

Protel have an ongoing issue that is biting them I think, that is that 
their libraries use hidden pin functionality for many object 
types.  Converting from that to explicit power pins is potentially hard and 
may break existing schematics.  I think they are in a bind.  There may need 
to be a deprecated set of libraries with hidden pins and VCC and GND pins 
on each part of multi-part logic devices to prevent breaking old designs, 
and a newer set of libraries that do things in a manner more compatible 
with the modern multi-rail and power management based designs.

I recommend that anyone using the Protel libraries copy the component from 
the lib into their own library and unhide all the hidden pins on all parts 
and the rejig the power pins to either one part having the single set of 
power pins or a separate power pin-only part. (The exception might be this 
experienced Protel designers that fully understand.... and even then they 
should expect some mistakes at times, usually when the pressure is on.) We 
are still waiting for the extension to ERC to allow checking that all parts 
of all components have been placed.

I think this is an area that that we should attempt to get some wide 
consensus and then put to Altium.  The alternative is that they will 
continue to produce what I think are broken libraries for all but a small 
minority of experienced users that wish to use hidden pins.  The use of 
hidden pins is becoming increasingly banned in companies of my 
acquaintance, with many now explicitly forcing the "all pins on the device 
must be shown on the sch" rule.

Back to Mike, your problem is the hidden pins automatically force a 
connection based on the net name (or lack of).  Your best bet is to either 
remove the pins or simply shown them in a box with suitable text inside the 
perimeter of the sch component.  Whatever you do, get rid of the hidden pins.

Ian Wilson


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