Gentlemen, those CD4x and 74HC libraries have two required
values that appear on a symbol's SpiceModel line.
ctrl-right-click a logic symbol to alter its SpiceModel line.
By default the two values are the nodes "VDD" and "0".
Creating a 12V power supply for CD4x logic and naming its
output node VDD works out-of-the-box.
But assume for example, you already have a V-24 node and a
V-12 node that could power the logic.
Change the logic symbol's default SpiceModel value from "VDD
0" to "V-12 V-24".
This sets logic outputs to be V(V-12)=logic-high and
V(V-24)=logic-low, instead of VDD/0.
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In either case the difference across the power pins is 12
volts, -12 to -24 volts or 12 to 0 volts has the same 12 volt
difference.
To power the internal logic from 12 volts, change the
symbol's default SpiceLine (not SpiceModel) value from VDD=5 to
VDD=12.
The SpiceLine VDD=x value sets the model's power-pin voltage
and can be anything like VDD=2.3 or 3.5, 6, 12 etc...
The three SpiceLine values control functions within the logic
like, prop-delay, output drive, slew rate, etc...
The SpiceLine SPEED=1.0 and TRIPDT=5e-9 are defaulted for the
logic family.
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Changing the VDD=x value affects the speed of a given device.
(i.e. CD4x is much faster at 15V than it is at 5V)
The SpiceLine SPEED=1.0 value is relative.
To model CD4x-like logic at 12 volts that is 10 times faster
than normal CD4x logic, change the SpiceLine SPEED=1.0 value to
SPEED=10.
This is not quite correct. The CD4000 parts do have the internal
"VDD" supply node, but in the 74HC parts, it is "VCC".
Tony Casey