As shown above, this function block type is modeled as a composite type using an instance of the FB_SEL_COLOR type and an instance of the OUT_COLOR type to display a colored circle with a label to its right. In practice, it is implemented as a subclass of OUT_COLOR .

When an event occurs at the REQ input while QI=TRUE , the color is updated to the value specified by the C0 or C1 input depending on whether the value of the IN input is FALSE or TRUE, respectively.

The input/output semantics of this FB type are as described below.

See the TESTBED_MVCL System configuration for examples of the use of instances of this type.

EVENT_INPUT
    INIT WITH QI,LABEL,IN,C0,C1; (* Initialization *)
    REQ WITH QI,IN,LABEL,C0,C1; (* Request *)
END_EVENT
EVENT_OUTPUT
    INITO WITH QO; (* Initialization Confirm *)
    CNF WITH QO; (* Service Confirmation *)
END_EVENT
VAR_INPUT
    QI : BOOL := true; (* 1=Output Enabled, 0=Disabled *)
    LABEL : WSTRING; (* Label *)
    IN : BOOL; (* Input value *)
    C0 : COLOR := COLOR#white; (* Color when IN=0 *)
    C1 : COLOR := COLOR#green; (* Color when IN=1 *)
END_VAR
VAR_OUTPUT
    QO : BOOL; (* 1=Output Enabled, 0=Disabled *)
END_VAR