Scan Parameters - GE PACSystems RX7i Reference Manual

3.2.5 Scan Parameters

These parameters determine the characteristics of CPU sweep execution.
Scan Parameters
Sweep Mode The sweep mode determines the priority of tasks the CPU performs during the sweep and
defines how much time is allotted to each task. The parameters that can be modified vary
depending on the selection for sweep mode.
The Controller Communications Window, Backplane Communications Window, and
Background Window phases of the PLC sweep can be run in various modes, based on the
PLC sweep mode.
Choices:
▪
▪
▪
Logic Checksum The number of user logic words to use as input to the checksum algorithm each sweep.
Words
Valid range: 0 through 32760, in increments of 8.
Default: 16.
Controller (Available only when Sweep Mode is set to Normal.) Execution settings for the Controller
Communication Communications Window.
Window Mode
Choices:
▪
▪
Default: Limited.
Note:
GFK-2222AD
Normal mode: The PLC sweep executes as quickly as possible. The overall PLC
sweep time depends on the logic program and the requests being processed
in the windows and is equal to the time required to execute the logic in the
program plus the respective window timer values. The window terminates
when it has no more tasks to complete. This is the default value.
Constant Window mode: Each window operates in a Run-to-Completion
mode. The PLC alternates among three windows for a time equal to the value
set for the window timer parameter. The overall PLC sweep time is equal to
the time required to execute the logic program plus the value of the window
timer. This time may vary due to sweep-to-sweep differences in the execution
of the program logic.
Constant Sweep mode: The overall PLC sweep time is fixed. Some or all of the
windows at the end of the sweep might not be executed. The windows
terminate when the overall PLC sweep time has reached the value specified
for the Sweep Timer parameter.
Complete: The window runs to completion. There is no time limit.
Limited: Time sliced. The maximum execution time for the Controller
Communications Window per scan is specified in the Controller
Communications Window Timer parameter.
This parameter corresponds to the Programmer Window Mode parameter on a
Series 90-70 PLC.
April 2018
Chapter 3. CPU Configuration
117