Chapter 4. CPU OperationGFK-2222AD April 2018 1474.3 Window ModesThe 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 CPUsweep mode. (Refer to CPU Sweep Modes.) The following three window modes are available:Run-to-CompletionIn Run-to-Completion mode, all requests made when the window has started areserviced. When all pending requests in the given window have completed, theCPU transitions to the next phase of the sweep. (This does not apply to theBackground window because it does not process requests.)Constant In Constant Window mode, the total amount of time that the ControllerCommunications window, Backplane Communications window, and Backgroundwindow 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 windowsthe specified amount of time polling for further requests. If any window is put inconstant window mode, all are in constant window mode.Limited In Limited mode, the maximum time is fixed for the execution of the window. Iftime expires while in the middle of servicing a request, the window is closed, andcommunications will be resumed the next time that the given window is run. If norequests are pending in this window, the CPU proceeds to the next phase of thesweep.
