GE PACSystems RX7i Reference Manual page 154

Phase Activity
Controller Services the onboard Ethernet and serial ports. In addition, reconfiguration of expansion
Communications racks and individual modules occurs during this portion of the sweep.
Window
The CPU always executes this window. The following items are serviced in this window:
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Time and execution of the Controller Communications Window can be configured using the
programming software. It can also be dynamically controlled from the user program using
Service Request function #3. The window time can be set to a value from 0 to 255 ms (default
is 10 ms).
Note that if the Controller Communications Window is set to 0, there are two alternate ways
to open the window: perform a power-cycle without the battery (or Energy Pack) attached, or
go to STOP Mode.
Backplane Communications with intelligent devices occur during this window. The rack-based Ethernet
Communications Interface module communicates in the Backplane Communications window. During this part
Window of the sweep the CPU communicates with intelligent modules such as the Genius Bus
Controller and TCP/IP Ethernet modules.
In this window, the CPU completes any previously unfinished request before executing any
pending requests in the queue. When the time allocated for the window expires, processing
stops.
The Backplane Communications Window defaults to Complete (Run to Completion) mode.
This means that all currently pending requests on all intelligent option modules are processed
every sweep. This window can also run in Limited mode, in which the maximum time allocated
for the window per scan is specified.
The mode and time limit can be configured and stored to the CPU, or it can be dynamically
controlled from the user program using Service Request function #4. The Backplane
Communications Window time can be set to a value from 0 to 255ms (default is 255ms). This
allows communications functions to be skipped during certain time-critical sweeps.
Background CPU self-tests occur in this window.
Window
A CPU self-test is performed in this window. Included in this self-test is a verification of the
checksum for the CPU operating system software.
The Background Window time defaults to 0 ms. A different value can be configured and stored
to the CPU, or it can be changed online using the programming software.
Time and execution of the Background Window can also be dynamically controlled from the
user program using Service Request function #5. This allows background functions to be
skipped during certain time-critical sweeps.
GFK-2222AD
Reconfiguration of expansion racks and individual modules. During the Controller
Communications Window, highest priority is given to reconfiguration. Modules are
reconfigured as needed, up to the total time allocated to this window. Several sweeps
are required to complete reconfiguration of a module.
Communications activity involving the embedded Ethernet port and the two serial ports
of the CPU.
April 2018
Chapter 4. CPU Operation
143