GE 90-30/20/Micro manual Svcreq #2 Read Window Values, Mode Name Value Description

4

SVCREQ #2: Read Window Values

Use SVCREQ function #2 to obtain the current window mode time values for the programmer communications window, the system communications window, and the background task window.

Note

Of the CPUs discussed in this manual, Service Request 2 is supported only by 90-30 CPUs, beginning with Release 8.0.

There are three modes for each window:

Mode Name	Value	Description
Limited Mode	0	The execution time of the window is limited to its respective
		default value or to a value defined using SVCREQ function #3
		for the programmer communications window or SVCREQ
		function #4 for the systems communications window. The
		window will terminate when it has no more tasks to complete.
Constant Mode	1	Each window will operate in a RUN TO COMPLETION mode, and
		the PLC will alternate among the three windows for a time
		equal to the sum of each window’s respective time value. If
		one window is placed in CONSTANT mode, the remaining two
		windows are automatically placed in CONSTANT mode. If the
		PLC is operating in CONSTANT WINDOW mode and a
		particular window’s execution time is not defined using the associated
		SVCREQ function, the default time for that window is used in the
		constant window time calculation.
Run to Completion	2	Regardless of the window time associated with a particular
Mode		window, whether default or defined using a service request
		function, the window will run until all tasks within that window are
		completed.

A window is disabled when the time value is zero.

The parameter block has a length of three words:

	High Byte	Low Byte
Programmer Window	Mode	Value in ms
System Communications Window	Mode	Value in ms
Background Window

address

address + 1

address + 2

All parameters are output parameters. It is not necessary to enter values in the parameter block to program this function. Output values for all three windows are given in milliseconds.

GFK-0467K Chapter 4 Series 90-30/20/Micro Instructions Set 4-137