Hi all,
I would like to propose to add "instance specific
symbol and pin attributes" promotion feature to
gEDA file format and data structure. Currently,
gEDA only support "instance specific symbol attribute"
overrides (in gEDA terminology, attribute promotion),
but no "instance specific symbol pin attributes"
overrides.
To implement a more general "instance specific
symbol and pin attributes" promotion, we can use
a format similar to the embedded component format:
C x y selectable angle mirror Instance_specific::basename
[
# Only P and T type, no "graphic" types i.e., A,G,V,etc:
T ....
symbol_attr=value
P ....
{
T ...
pin_attr=value
}
]
The "instance specific pin attributes" overrides feature
is available in some advance VLSI EDA schematic capture tool.
It helps to ease the implementation of many down stream
tools such as FanIn/FanOut, Logical Effort(LE),
Pin_to_pin_delay, VHDL_Vital, etc.
Of course, due to the flexibility of current gEDA
architecture, the above is not absolutely necessary,
since the down stream tools can always use Symbol
Attributes to emulate symol_pin attribute, e.g.,
"pin1_fanin=2", etc., though not very convenient.
Best Regards,
Paul Tan
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