Rockwell Automation 1746-XXXX SLC 500 4-Channel Analog I/O Modules User Manual - Manual (Page 71)

Publication 1746-UM005B-EN-P - June 2004
Programming Examples 6-9
The out-of-range limits are predetermined because any value less than
0% is 6,242 and any value greater than 100% is 31,208. The ladder
logic checks for the out-of-range flag to verify that not less than 4 mA
and not more than 20 mA is provided out of the analog output
channel.
The percentage of valve opening may be input to the processor by:
•
entering the data through a DTAM or HHT
•
MOVing the data from thumb wheels or a keypad (possibly
converting the data from BCD using FRD instruction)
The percentage of valve opening may be output for operator interface
by:
•
monitoring the data using a DTAM or HHT
•
MOVing the data to an output module as variable data to a
Dataliner
•
converting the data to BCD (using TOD instruction) and
MOVing it to an LED display
Since the slope is greater than 3.2767 only standard math can be used
for the ladder diagram with SLC 500 fixed, SLC 5/01, 5/02, 5/03
(OS300 or OS301), and 5/04 (OS400) processors. The ladder diagram
prevents a processor fault by unlatching the mathematical overflow bit
S2:5/0 before the end of the scan. Refer to the example ladder
diagram on the next page. Following the standard math example is a
ladder diagram using the SCP instruction, available only in the SLC
5/03 (OS302 or later), SLC 5/04 (OS401 or later), and SLC 5/05.