Rockwell Automation 1761 MicroLogix 1000 Programmable Controllers - Manual (Page 299)

Programming Reference
B–11
Address Description Classification Bit
S:3L Current Scan
Time Status The value of this byte tells you how much time
elapses in a program cycle. A program cycle
includes:
•
scanning the ladder program,
•
housekeeping,
•
scanning the I/O,
•
servicing of the communication channel.
The byte value is zeroed by the controller each
scan, immediately preceding the execution of
rung 0 of program file 2 (main program file).
The byte is incremented every 10 ms
thereafter, and indicates, in 10 ms increments,
the amount of time elapsed in each scan. If
this value ever equals the value in S:3H
Watchdog, a user watchdog major error will be
declared (code 0022).
The resolution of the scan time value is
+
0 to
90 ms (–10 ms). Example: The value 9
indicates that 80–90 ms has elapsed since the
start of the program cycle.
S:3H Watchdog
Scan Time Dynamic
Configuration This byte value contains the number of 10 ms
ticks allowed to occur during a program cycle.
The default value is 10 (100 ms), but you can
increase this to 255 (2.55 seconds) or
decrease it to 1, as your application requires.
If the program scan S:3L value equals the
watchdog value, a watchdog major error will be
declared (code 0022).
Reference