Rockwell Automation Logix5000 Controllers Function Block Diagram Programming Manual - Manual (Page 19)

Program a Function Block Diagram Chapter 1
example, the operator sets the OperOperReq input from a faceplate to take
control of that instruction. This example shows how to lock an instruction into
Program control.
Operator request inputs to an instruction are always cleared by the instruction
when it executes. This lets operator interface work with these instructions by
setting the desired mode request bit. You do not have to program the operator
interface to reset the request bits. For example, if an operator interface sets the
OperAutoReq input to a PIDE instruction, when the PIDE instruction executes,
it determines the appropriate response and clears the OperAutoReq.
Program request inputs are not normally cleared by the instruction because these
are normally wired as inputs into the instruction. If the instruction clears these
inputs, the input would get set again by the wired input. There might be situations
where you want to use other logic to set the Program requests to be cleared by the
instruction. In this case, set the ProgValueReset input and the instruction always
clears the Program mode request inputs when it executes.
In this example, a rung of ladder logic in another routine is used to one-shot latch
a ProgAutoReq input to a PIDE instruction when a push button is pushed.
Because the PIDE instruction automatically clears the Program mode requests,
you do not have to write any ladder logic to clear the ProgAutoReq input after
the routine executes. The PIDE instruction receives only one request to go to
Auto every time the push button is pressed.
Rockwell Automation Publication 1756-PM009E-EN-P - October 2014 19