User`s guide

7
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28 Di
g
ital Device Modelin
g
.subckt DtoA_STD D A DPWR DGND
+ params: DRVL=0 DRVH=0 CAPACITANCE=0
*
N1 A DGND DPWR DIN74 DGTLNET=D IO_STD
C1 A DGND {CAPACITANCE+0.1pF}
.ends
For this subcircuit, the DRVH and DRVL parameters values
specified in the IO_STD model would be passed to it. (The
interface subcircuits in the model libraries do not currently use
these values.) The DtoA_STD interface subcircuit references
the DIN74 model in its PSpice A/D N device declaration. This
model, stated elsewhere in the libraries, describes how to
translate a digital state into a voltage and impedance.
.model DIN74 dinput (
+ s0name="0" s0tsw=3.5ns s0rlo=7.13
+ s0rhi=389 ; 7ohm, 0.09v
+ s1name="1" s1tsw=5.5ns s1rlo=467
+ s1rhi=200 ; 140ohm, 3.5v
+ s2name="X" s2tsw=3.5ns s2rlo=42.9
+ s2rhi=116 ; 31.3ohm, 1.35v
+ s3name="R" s3tsw=3.5ns s3rlo=42.9
+ s3rhi=116 ; 31.3ohm, 1.35v
+ s4name="F" s4tsw=3.5ns s4rlo=42.9
+ s4rhi=116 ; 31.3ohm, 1.35v
+ s5name="Z" s5tsw=3.5ns s5rlo=200K
+ s5rhi=200K
+)
Each state is turned into a pullup and pulldown resistor pair to
provide the correct voltage and impedance. The Z state is
accounted for as well as the 0, 1, and X logic levels.
You can create your own interface subcircuits, DINPUT
models, DOUTPUT models, and I/O Models like these for
technologies not currently supported in the model libraries.
MicroSim recommends that you save these in your own custom
model library, which you can then configure for use with a given
schematic.
The DINPUT model parameters
are described under PSpice A/D
N devices in the online
MicroSim
PSpice A/D Reference Manual
.