Specifications

70 Chapter 4—Simulation
A pin delay acts like a “buffer” device with the given delay inserted inline
with the pin. On an input pin, the device simulation model will not see a
change in signal value until after the pin delay has elapsed. On an output pin,
the pin delay is added to the overall device delay for any changes scheduled
on that pin.
Setting the Delay
To set the delay for a device, first select the device by clicking on it. Then
choose Simulation Params from the Simulation menu.
A dialog box will appear, allowing you to increase or decrease the delay
value by clicking one of two buttons. The minimum delay value is 0 and
the maximum is 32,767. When the delay setting for a subcircuit device is
changed, the delays for all internal devices are changed by the same
amount.
Effect of Zero Delay
A delay value of zero is permitted in a LogicWorks device, but this setting
should be used only with an understanding of how the simulation is imple-
mented—as it can result in unexpected side effects.
Note that on a given pass through the simulation routine, all the events on
the list which occur at the current time are scanned and then the new out-
puts for all affected devices are calculated. If any of these devices has a
zero delay setting, then this will result in more changes being placed on the
event list at the current time. However, all these changes emerging from
zero–delay devices will not be evaluated until the next pass through the
simulator. This is done to allow for user interaction with the simulation.
If you step interactively through a circuit with zero–delay elements, you
will see all these value changes updated on the screen, even though “simu-
lation time” does not advance. If a signal changes value and then reverts to
its original state within the same time step, this will be displayed as a zero–
width spike in the Timing window.
If a zero–delay feedback loop exists in a circuit, the signal changes will be
simulated and any probes on the diagram will be updated at each pass
through the simulator. However, the events at the head of the list will
always have the same time value associated with them and the simulated
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