Chapter 4. Ladder Diagram (LD) ProgrammingGFK-2950C February 2018 854.3.2 Graphical Representation of CoilsThe programming software displays the COIL, NCCOIL, SETCOIL, and RESETCOIL instructionsdifferently depending on the retentive state of the BOOL variables assigned to them. Examples areprovided in the discussion of each type of coil. For a discussion of retentiveness, refer toRetentiveness of Logic and Data in Chapter 3.Coil (Normally Open)A retentive variable is assigned to the coil A non-retentive variable is assigned to the coilWhen a COIL receives power flow, it sets its associated BOOL variable ON (1). When it receives nopower flow, it sets the associated BOOL variable OFF (0). COIL can be assigned a retentive variableor 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-discretememory, are also permitted.Continuation CoilA continuation coil instructs the PLC to continue the present rung's LD logic power flowvalue (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 haveassociated 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 CoilA retentive variable is assigned to the negatedcoilA non-retentive variable is assigned to the negatedcoilWhen it does not receive power flow, a negated coil (NCCOIL) sets a discrete reference ON. When itdoes receive power flow, NCCOIL sets a discrete reference OFF. NCCOIL can be assigned a retentivevariable 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-discretememory, are also permitted.
