Ltch Function Block - Honeywell UMC800 Reference Manual

2.33 LTCH Function Block

Description
The LTCH label stands for Latch. This block is part of the Logic and Fast Logic categories. It looks like
this graphically on the Control Builder.
Function
Latches output (OUT) ON when latch input (L) turns ON and maintain latched output until unlatch input
(U) turns ON. Note that latch input must be OFF for unlatch input to work.
• If U = ON, then: OUT = OFF.
• If L = ON, then: OUT = ON.
• Else, OUT = Previous State.
Input
L = Latch Command Digital signal.
U = Unlatch Command Digital signal.
Output
OUT = Digital signal
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.
3/99
OR
Fast Logic
Function Block Reference Guide
Function Blocks
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