Rockwell Automation 6723-PCO DATA PROCESS CONFIG OPERATIO - Manual (Page 15)

Process Configuration and Operation Software for Windows t 13
Publication 6723Ć10.1 Ć August 1996
The grain-drying application in our example also requires the
control of a conveyor motor (HS102), which is a two-state,
discrete device. You can use the DD2 function to control it. You
should enter a 1 in the “DD2 Device Drivers” row.
You can assume that the motor is controlled by one PLC output.
State 1 (output closed) turns the motor on, and state 0 (output
open) turns the motor off. This is the output of the DD2 function.
You can also assume that the motor provides one feedback signal,
attached to one PLC input, FB0. When FB0 is set to 1, it
indicates that the motor is rotating; when FB0 is set to 0, the
motor is not rotating. This is the feedback input of the DD2
function. In the grain drying example, you will not use DD2’s
FB1 input.
Keep the following items in mind when filling out this section:
•
Regulatory (PID) loops count as one function; cascade loops
count as two functions.
•
You can determine zero-state, two-state/three-state device
drivers by counting all the digital valves, motors, etc. present
in your application.
•
PCO comes configured for one PanelView per PLC processor
(racks 6 and 7).
Once you have entered the number of PCO functions, the System
Summary section of the Sizing Spreadsheet will provide you with
the following information:
•
the number of JSRs required for your application
Every JSR represents one instance of the function. In our
example, then, you should write one JSR for the DD2
function, two JSRs for the PID function, and one JSR for the
N-Series function (to handle all eight channels at once).
•
the total PLC memory required for your application
The grain-drying example requires:
– 16.5K of program and data file memory
– 30.5 ms of scan time
– 375 tags, if you are using the RSView MMI system
This example shows that a PLC-5/30 processor might be large
enough to fit the application, as long as your own custom logic
does not exceed 15.5K (i.e. 32K minus 16.5K, as required by
the grain-drying application).
•
the calculated execution time, based on non-STI PLC-5/60,
series C