Download Modicon 984 Programmable Controller Systems Manual

8.3
Normal and Latched Coils
A coil is a discrete output value represented by a 0x reference number. Because
output values are updated in State RAM by the controller’s CPU, a coil may be
used internally in the logic program or externally via the Traffic Cop to a discrete
output module. Coils are either OFF or ON, depending on power flow in the logic
program. When a coil is ON, it may either pass power to a discrete output circuit
on the shop floor or change the state of an internal relay contact in state RAM.
There are two types of coils:
Normal Coil
A normal coil is turned OFF if power at the controller is removed.
Latched Coil
L
If a latched coil has been energized at the time of a controller power loss, the coil
will come back up in the same state for one scan once power has been restored.
Physical
Input
Ladder
Logic
Physical
Output
Input
10001 Module
Output
Module 00001
10001
Closing the
Pushbutton ...
124
Contacts, Shorts, and Coils
00001
... Turns ON
the Light
GM--0984--SYS