Specifications

Device Simulation Characteristics 71
time will never advance. This will stop the Timing window from updating
until some delay is inserted in the loop.
Where Delays are Stored
For devices, the delay attribute field is called “Delay.Dev”; for pins, it is
“Delay.Pin”. An empty or invalid string will be interpreted as the default
value, usually 1 for devices and 0 for pins.
Some special–purpose devices, such as the Clock and One Shot primitive
devices, take two delay characteristics. In this case, two integers separated
by a comma should appear in the Delay.Dev field.
 More information on this is given in the information section on each of
these primitive types in Chapter 9, Primitive Devices.
Device Storage State
In LogicWorks, primitive storage devices (such as flip–flops, counters, and
registers) do not store their current state internally. The device state is com-
pletely determined by the values on the signals attached to the output pins.
Thus, the following factors will affect the operation of these devices:
 Conflicting or overriding values on the output signals (e.g., a stuck
state) will override the last device state calculated by the model.
 Device and pin delays will influence the calculation of a new device
state. For example, if the period of a clock applied to a counter is less
than the total delay through it, an erroneous count sequence will result.
If desired, this behavior can be modified by placing the primitive devices in
a subcircuit device and setting appropriate pin types and delays on the par-
ent device to “buffer” the outputs.
NOTE: These comments do not apply to RAM or bidirectional switch primitives,
both of which store internal state information independent of the values of
the attached signals.
 See the section “Working With Subcircuit Devices” in Chapter 7,
Simulation, for more information.
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