Rockwell Automation DeviceLogix System User Manual - Manual (Page 26)

26 Publication RA-UM003B-EN-P - February 2010
Chapter 2 Navigate the Function Block Editor Interface
• Once the Trig Finish event occurs, or if a Retrigger event is
detected, or the Late Finish status is reported, the function block
stops operation, and the internal timer stops timing. The
function requires a reset event to perform another operation.
• In all cases, the Reset signal overrides all other function block
functionality. If the Reset Binding attribute is not supported or it
is not bound, the function block behaves as if it is tied low.
• All input edges that occur during reset are ignored.
• The Elapsed Time attribute should be clear at the time that the
Trig Start event triggers the function block.
PID
Use the PID function block to control a closed single analog loop.
The PID function block operates only in the timed mode. In this
mode, the function block is calculated and updates its output
periodically at a user-selectable rate. PID closed loop control holds a
process variable at a desired set point. A flow rate/fluid level example
is shown in the following figure.
Parameters Data Range
MinTime 0 ~ 65535
RangeTime 0 ~ 65535
ElapsedTime 0 ~ 65535
Σ Σ