User`s guide

Input/Output Characteristics 7
-27
If an instance of the 74393 part is connected to an analog part
via node AD_NODE, PSpice A/D generates an interface block
using the I/O Model specified by the digital primitive actually at
the interface. Suppose that U1 is the primitive connected at
AD_NODE (see the 74393 subcircuit definition on page 9), and
that the IO_LEVEL is set to 1. PSpice A/D determines that
IO_STD is the I/O Model used by U1. Notice how IO_STD
identifies the interface subcircuit names AtoD_STD and
DtoA_STD to be used for level 1 subcircuit selection. If the
connection with U1 is an input (e.g., a clock line), PSpice A/D
creates an instance of the subcircuit AtoD_STD:
X$AD_NODE_AtoD1 AD_NODE AD_NODE$AtoD
$G_DPWR $G_DGND
+ AtoD_STD
+ PARAMS: CAPACITANCE=0
The AtoD_STD interface subcircuit references the DO74 model
in its PSpice A/D O device declaration. This model, stated
elsewhere in the model libraries, describes how to translate an
analog signal on the analog side of an interface node, to a digital
state on the digital side of an interface node.
.model DO74 doutput
+ s0name="X" s0vlo=0.8 s0vhi=2.0
+ s1name="0" s1vlo=-1.5 s1vhi=0.8
+ s2name="R" s2vlo=0.8 s2vhi=1.4
+ s3name="R" s3vlo=1.3 s3vhi=2.0
+ s4name="X" s4vlo=0.8 s4vhi=2.0
+ s5name="1" s5vlo=2.0 s5vhi=7.0
+ s6name="F" s6vlo=1.3 s6vhi=2.0
+ s7name="F" s7vlo=0.8 s7vhi=1.4
+
Supposing the output of the 74393 is connected to an analog part
via the digital primitive UBUFF. At IO_LEVEL set to 1, PSpice
A/D determines that the DtoA_STD interface subcircuit
identified in the IO_STD model, should be used.
The DOUTPUT model
parameters are described under
O devices in the online
MicroSim
PSpice A/D Reference Manual
.