GFK-0467K Chapter 4 Series 90-30/20/Micro Instructions Set 4-3
4
Using Coils Coils are used to control discrete references. Conditional logic must be used to control the flow of
power to a coil. Coils cause action directly; they do not pass power flow to the right. If additional
logic in the program should be executed as a result of the coil condition, an internal reference
should be used for that coil or a continuation coil/contact combination may be used.
Coils are always located at the rightmost position of a line of logic. A rung may contain up to eight
coils.
The type of coil used will depend on the type of program action desired. The states of retentive
coils are saved when power is cycled or when the PLC goes from STOP to RUN mode. The states
of non-retentive coils are set to zero when power is cycled or the PLC goes from STOP to RUN
mode.
Table 4-2. Types of Coils
Type of Coil Display Power to Coil Result
Normally —()— ON Set reference ON.
Open OFF Set reference OFF.
Negated —(/)— ON Set reference OFF.
OFF Set reference ON.
Retentive —(M)— ON Set reference ON, retentive.
OFF Set reference OFF, retentive.
Negated —(/M)— ON Set reference OFF, retentive.
Retentive OFF Set reference ON, retentive.
Positive
Transition —(↑)— OFF→ON If reference is OFF,set it ON for one sweep.
Negative
Transition —(↓)— ON←OFF If reference is OFF, set it ON for one sweep.
SET —(S)— ON Set reference ON until reset OFF by —(R)—.
OFF Do not change the coil state.
RESET —(R)— ON Set reference OFF until set ON by —(S)—.
OFF Do not change the coil state.
Retentive SET —(SM)— ON Set reference ON until reset OFF by —(RM)—,
retentive.
OFF Do not change the coil state.
Retentive —(RM)— ON Set reference OFF until set ON by —(SM)—,
retentive.
RESET OFF Do not change the coil state.
Continuation ——<+> ON Set next continuation contact ON.
Coil OFF Set next continuation contact OFF.