Publication 1766-RM001A-EN-P - October 2008
Process Control Instruction
331
PD Data File
The PID instruction implemented by the MicroLogix 1400 controllers is
virtually identical in function to the PID implementation used by the
Allen-Bradley SLC 5/03 and higher processors. Minor differences primarily
involve enhancements to terminology. The major difference is that the
PID instruction now has its own data file. In the SLC family of processors,
the PID instruction operated as a block of registers within an integer file.
The Micrologix 1400 PID instruction utilizes a PD data file.
You can create a PD data file by creating a new data file and classifying it
as a PD file type. RSLogix automatically creates a new PD file or a PD
sub-element whenever a PID instruction is programmed on a rung. The
PD file then appears in the list of Data Files as shown in the illustration.
Each PD data file has a maximum of 255 elements and each PID
instruction requires a unique PD element. Each PD element is composed
of 20 sub-elements, which include bit, integer and long integer data. All of
the examples in this chapter use PD file 10 sub-element 0.
PD file created by RSLogix
500/RSLogix Micro.
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