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4.3.2
Graphical Representation of Coils
The programming software displays the COIL, NCCOIL, SETCOIL, and RESETCOIL instructions
differently depending on the retentive state of the BOOL variables assigned to them. Examples are
provided in the discussion of each type of coil. For a discussion of retentiveness, refer to
Retentiveness of Logic and Data in Chapter 3.
Coil (Normally Open)
A retentive variable is assigned to the coil
When a COIL receives power flow, it sets its associated BOOL variable ON (1). When it receives no
power flow, it sets the associated BOOL variable OFF (0). COIL can be assigned a retentive variable
or a non-retentive variable.
Valid memory areas: %I, %Q, %M, %T, %SA - %SC, and %G. Symbolic discrete variables are permitted.
Bit-in-word references on any word-oriented memory except %AI, including symbolic non-discrete
memory, are also permitted.
Continuation Coil
A continuation coil instructs the PLC to continue the present rung's LD logic power flow
value (TRUE or FALSE) at the continuation contact on a following rung.
The flow state of the continuation coil is passed to the continuation contact.
Notes:
If the flow of logic does not execute a continuation coil before it executes a continuation contact,
■
the state of the continuation contact is no flow (FALSE).
The continuation coil and the continuation contact do not use parameters and do not have
■
associated variables.
You can have multiple rungs with continuation contacts after a single continuation coil.
■
You can have multiple rungs with continuation coils before one rung with a continuation contact.
■
Negated Coil
A retentive variable is assigned to the negated
coil
When it does not receive power flow, a negated coil (NCCOIL) sets a discrete reference ON. When it
does receive power flow, NCCOIL sets a discrete reference OFF. NCCOIL can be assigned a retentive
variable or a non-retentive variable.
Valid memory areas: %I, %Q, %M, %T, %SA - %SC, and %G. Symbolic discrete variables are permitted.
Bit-in-word references on any word-oriented memory except %AI, including symbolic non-discrete
memory, are also permitted.
GFK-2950C
Chapter 4. Ladder Diagram (LD) Programming
A non-retentive variable is assigned to the coil
A non-retentive variable is assigned to the negated
coil
February 2018
85
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