86
6)
Assign a tag to the XIO element.
a)
Double-click on the XIO element located to the left of the MSG block. Type in N20:0/15
(MSG instruction’s enable bit). This configuration causes the MSG instruction to
automatically retrigger itself when it completes. While this is acceptable for the purposes of
this example, it can produce high network utilization. In actual practice, it may be desirable to
incorporate additional logic elements to allow triggering the MSG instruction at a specific rate
or under specific conditions.
7)
The program is now complete. Refer to Figure 116.
Figure 116: Completed PLC Program
8)
Save, download, and run the program.
a)
To view the registers being read from the interface card, double-click the data file N18 under
“Data Files” in the controller organizer view. 25 register values starting at register #2050 are
being continuously read from the interface card and placed in the 25 sequential offsets of
N18 starting at N18:1. Refer to Figure 117. We can see that N18:9 (register 2058 / output
frequency / function code M09) has a value of 2525 (25.25Hz), N18:12 (register 2061 /
output voltage / function code M12) has a value of 610 (61.0V), etc.
Figure 117: Monitoring the Data Being Read from the Inverter
8.3.4 SLC-5/05
Example:
Read a Single Register
The configuration and execution for reading a single register is in general identical to that required for
reading a block of registers as detailed in section 8.3.3. The only difference is in the configuration of the
MSG instruction. Figure 118 shows an example MSG instruction’s General tab, which will read a single
element (N30:58, which corresponds to register 2058 / output frequency / function code M09) and place
it in the first element (offset 0) of N18.
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