Rockwell Automation 8520-ARM2 9/Series CNC AMP Reference Manual Documentation Set - Manual (Page 660)

Miscellaneous Parameters
Chapter 37
37-20
Function
This parameter specifies the system scan time. This is the time interval that
is used to restart the time critical functions of the control (system
foreground). The system interrupts the lower-priority tasks (system
background) at this interval.
Parameter
Number
625
Range
Selection Result Selection Result
(a) 6 ms (h) 20 ms
(b) 8 ms (i) 22 ms
(c) 10 ms (j) 24 ms
(d) 12 ms (k) 26 ms
(e) 14 ms (l) 28 ms
(f) 16 ms (m) 30 ms
(g) 18 ms
Notes
This parameter must be set high enough to allow completion of the
time-critical functions, and to provide sufficient time for system tasks that
execute over several scans. The following subsections provide information
to guide you in setting this parameter correctly for your application.
The 9/230 and 9/260 should not be set lower than 8 ms.
For Dual Processing controls, the minimum setting for the 9/260 is 14ms,
and the minimum setting for the 9/290 is 10ms.
Your minimum block cycle time is determined by the system background
scan time. Part program blocks are decoded during the system
background. The system scan time you configure in AMP impacts the
system background time and ultimately your minimum block cycle time.
Refer to the following section titled Analyzing Your System Timing.
37.23
System Scan Time