Program Scheduling Modes; Window Modes - GE PACSystems RXi User Manual

Chapter 5. CPU Operation

Program Scheduling Modes

5.2
The CPU supports one program scheduling mode, the Ordered mode. An ordered program is
executed in its entirety once per sweep in the Logic Window.

Window Modes

5.3
The previous section describes the phases of a typical CPU sweep. The Controller
Communications, Backplane Communications, and Background windows can be run in
various modes, based on the CPU sweep mode. (CPU sweep modes are described in detail
on page 75.) The following three window modes are available:
Run-to-
Completion
Constant
Limited
78
In Run-to-Completion mode, all requests made when the window has started
are serviced. When all pending requests in the given window have completed,
the CPU transitions to the next phase of the sweep. (This does not apply to the
Background window because it does not process requests.)
In Constant Window mode, the total amount of time that the Controller
Communications window, Backplane Communications window, and
Background window run is fixed. If the time expires while in the middle of
servicing a request, these windows are closed, and communications will be
resumed the next sweep. If no requests are pending in this window, the CPU
cycles through these windows the specified amount of time polling for further
requests. If any window is put in constant window mode, all are in constant
window mode.
In Limited mode, the maximum time that the window runs is fixed. If time
expires while in the middle of servicing a request, the window is closed, and
communications will be resumed the next time that the given window is run. If
no requests are pending in this window, the CPU proceeds to the next phase of
the sweep.
PACSystems* RXi Distributed IO Controller User Manual GFK-2816F