User`s guide

Input/Output Characteristics 7
-25
Creatin
g
Your Own Interface
Subcircuits for
Additional Technolo
g
ies
If you are creating custom digital parts for a technology which
is not in the model libraries, you may also need to create AtoD
and DtoA subcircuits. The new subcircuits need to be referenced
by the I/O Models for that technology. The AtoD and DtoA
interfaces have specific formats, such as node order and
parameters, which are expected by PSpice A/D for mixed-signal
simulations.
If you are creating parts in one of the logic families already in
the model libraries, you should reference the existing I/O
Models appropriate to that family. The I/O Models, in turn,
automatically reference the correct interface subcircuits for that
family. These, too, are already contained in the model libraries.
The AtoD interface subcircuit format is shown here:
.SUBCKT ATOD < name suffix >
+ <
analog input node >
+ <
digital output node >
+ <
digital power supply node >
+ <
digital ground node >
+ PARAMS: CAPACITANCE=<
input load value >
+ {
O device, loading capacitor, and other
+ declarations
}
.ENDS
It has four nodes as described. The AtoD subcircuit has one
parameter, CAPACITANCE, which corresponds to the input
load. PSpice A/D passes the value of the I/O Model parameter
INLD to this parameter when the interface subcircuit is called.