Publication 1747-RM001G-EN-P - November 2008
B-42 SLC Status File
S:22 Status Maximum Observed Scan Time
This word indicates the maximum observed interval
between consecutive scans.
Consecutive scans are defined as intervals between file
2/rung 0 and the END, TND, or the REF instruction. This
value indicates, in 10 ms increments, the time elapsed in
the longest program cycle of the processor. The processor
compares each last scan value to the value contained in
S:22. If the processor determines that the last scan value is
larger than the value stored at S:22, the last scan value is
written to S:22.
Resolution of the maximum observed scan time value is + 0
to -10 ms. For example, the value 9 indicates that 80 to 90
ms was observed as the longest program cycle.
Interrogate this value using the Data Monitor function if you
need to determine or verify the longest scan time of your
program.
••••
The Scan Time Selection Bit (S:33/13) determines the
timebase used for average and maximum Scan Times. When
clear, operation is as described above. When set, the
timebase is expressed in 1 ms increments (instead of 10 ms
increments). When S:33/13 is set, resolution of the
maximum observed scan time value is + 0 to -10 ms. For
example, the value 9 indicates that 8 to 9 ms was observed
as the largest program cycle.
•••
S:23 Status Average Scan Time
This word indicates a weighted running average time. The
value indicates, in 10 ms increments, the time elapsed in
the average program cycle of the processor.
For every Scan t:
Avg = (Avg * 7)
+ Scan
t
8
Resolution of the average scan time value is + 0 to -10 ms.
For example, the value 2 indicates that 10 to 20 ms was
calculated as the average program cycle.
••••
The Scan Time Selection bit S:33/13 determines the
timebase used for average Scan time. When clear,
operation is as described above. When set, the timebase is
expressed in 1 ms increments (instead of 10 ms increments).
When S:33/13 is set, resolution of the average scan time
value is + 0 to -10 ms. For example: the value 2 indicates
that 1 to 2 ms was calculated as the average program cycle.
•••
Table B.4 Status File Functions (Continued)
Address Classification Description Fixed
5/01
5/02 5/03 5/04 5/05
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