Rockwell Automation 9323-S5500D A.I. SERIES MICROLOGIX 1000 AND PLC-500 SOFTW - Manual (Page 228)

MicroLogix 1000 and PLC-500 A.I. Series Software Reference
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If the address is used as a file, such as a control block for a COP instruction, the
address will be shown in the format, _F: fn : wn l% fl where:
_F indicates file usage
fn is the file number
wn is the starting word number
l% indicates that the next number is the file length
fl is the file length (in words)
For example, if the system shows “_F:N7:0l%11”, this means file N7:0, with a file
length of 11 words.
Note You can configure the rung descriptions on and off with [F6] Utility [F8] Config . See
Chapter 12 - Customizing PLC-500 A.I. for details.
4. To move to one of the rungs listed, use the arrow keys to highlight the rung
number reference and press [Enter] .