User`s guide

4 Di

ital Simulation

Stren

ths

When a digital node is driven by more than one device,

PSpice A/D must determine the correct level of the node. Each

output has a strength value, and PSpice A/D compares the

strengths of the outputs driving the node. The strongest driver

determines the resulting level of the node. If outputs of the same

strength but different levels drive a node, the node’s level

becomes X.

PSpice A/D supports 64 strengths. The lowest (weakest)

strength is called Z. The highest (strongest) strength is called the

forcing strength. The Z strength (called high impedance) is

typically output by disabled tristate gates or open-collector

output devices. The program reports any nodes of Z strength (at

any level) as Z, and reports all other nodes by the designations

shown in Table 14-1

For additional information on this

topic see

Defining Output

Strengths on pa

e 7-21of

Chapter 7,Digital Device

Modeling.