Trig Function Block; Figure 2-79 Trig Function Block Example - Honeywell UMC800 Reference Manual

Function Blocks

2.75 TRIG Function Block

Description
The TRIG label stands for Trigger or "One Shot" operation. This block is part of the Logic and Fast
Logic categories. It looks like this graphically on the Control Builder.
Function
Turns a Logic output (OUT) ON for one logic scan cycle, when a logic input (X)goes from OFF to ON.
•
If X = ON and previous value of X was OFF, then: OUT = ON (one scan)
•
Otherwise, OUT = OFF
Input
X = Trigger command signal
Output
OUT = triggered pulse
ATTENTION: The duration of the logic pulse output is one function block execution cycle. The duration of
the fast logic pulse output in00 ms, or the fast logic cycle time.
Block Properties
Double click on the function block to access the function block properties dialog box.
Block Order (Read Only)
You can change the assigned execution order number by selecting "Execution Order" in the "Configure"
menu and arrange the order to suit your control strategy.
Example
Figure 2-79 shows a Function Block Diagram using a TRIG function block. An OFF delay timer block
output is ON as long as the RST input is logic HI (ON). It can be used for time duration but must be
triggered by an ON to OFF transition on the Reset input. This can be accomplished using Trigger blocks
(TRIG) to create one-shot pulses which last one scan cycle. The fast logic trigger pulse will last 100 ms.
while the normal logic trigger pulse will last the complete scan cycle for analog blocks. Use according to
application need. A Periodic timer output pulse may also be used to start the timer for the OFF delay.
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OR

Figure 2-79 TRIG Function Block Example

Function Block Reference Guide
Fast Logic
Timing Diagram
AND4 output
TRIG1 output
Off delay
OFDT2 output
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