The "trigger" pseudo-element
----------------------------------------------
Abstract

The "trigger" pseudo-element senses a state change, and propagates its
time.  It is primarily used to time shift waveforms.
----------------------------------------------
Syntax
	trigger <name> <expression>
----------------------------------------------
BNF

trigger: 'trigger' name logic_expression '\n'
----------------------------------------------
Description

The name of a trigger is referenced in a time expression:

  Vwave (pin gnd) V=[Wave](T-TR)

states that the value of the voltage is determined by the table "[Wave]",
using the time the trigger TR is activated as an offset to the actual
time (T).

A trigger is activated when the <expression> changes from false to
true.
----------------------------------------------
Uses in IBIS 3.2

Triggers are used to activate waveform generation.  "Example 1" uses a
control node, passed in, to activate it, for the normal rising and
falling waveforms.  "Example 2" shows the trigger being activated by
an internal signal condition, in this case as part of bus hold.
----------------------------------------------
Examples

Example 1:
  trigger  TR	(Logic(control) == 1)
  trigger  TF	(Logic(control) == 0)

The trigger "TR" is activated when the logic value of the node "control" 
becomes "1".

Example 2:
  trigger  TRraw (V(pin) > [Submodel_Spec]V_Trigger_r)
  trigger  TFraw (V(pin) < [Submodel_Spec]V_Trigger_f)
  trigger  TRise (TRraw || TFraw + [Submodel_Spec]Off_delay)
  trigger  TFall (TFraw || TRraw + [Submodel_Spec]Off_delay)

The trigger "TRraw" is activated when the voltage at the node "pin"
rises past the value stated in the parameter [Submodel_Spec]V_Trigger_r.

The trigger "TRise" is activated either at the same time as "TRraw" or 
"[Submodel_Spec]Off_delay" after "TFraw".
----------------------------------------------
----------------------------------------------
