State Industries GFK-0827 manual CPU Mode Switch, Valid Operating Mode Selection

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CPU Mode Switch

A three-position toggle switch is mounted near the top of the CPU board. This switch selects one of three operating modes for the CPU: RUN/ENABLED,RUN/DISABLED, or STOP. Although the mode of operation for the CPU can be controlled from both the switch and the programmer, the switch position restricts the ability of the programmer to put the CPU into certain modes.

The following table shows the modes that can be selected by the programmer based upon the position of the CPU mode switch.

Table 2. Valid Operating Mode Selection

CPU Mode Switch	Allowable Programmer
Position	Mode Command
	STOP
RUN/OUTPUTSENABLED	RUN/DISABLED
	RUN/ENABLED
	STOP
RUN/OUTPUTSDISABLED	RUN/DISABLED
STOP	STOP

Run/Outputs Enabled

The top position of the switch is Run with Outputs Enabled. With the switch in this position, the CPU executes all portions of the sweep normally.

Run/Outputs Disabled

The middle position of the switch is Run with Outputs Disabled. When the switch is in this position, the CPU executes all portions of the sweep normally, but physical outputs are held in their default state, and therefore remain unchanged. Refer to Chapter 4, page 65 for important information on the Run/Disabled mode in a Hot Standby CPU Redundancy system.

STOP

NOTE

TheSTOP/IOSCAN mode is not a valid mode in a redundancy system.

Refer to Chapter 4 for detailed information.

The bottom position of the switch is labeled STOP. With the switch in this position, the CPU communicates only with the programmer and devices connected to the serial port, and recovers faulted modules. Any of the values in the I/O tables can be changed using the programming computer.

16 Series 90-70 Hot Standby CPU Redundancy User's Guide ± December 1993 GFK-0827