Hardware reference guide

CPU Modules
170
35013379 02 October 2007
Key Switch The key switch is used to protect memory from programming changes while the
controller is in operation. The following figure shows the key switch.
The following table shows the key switch information.
Note: The key switch positions shown next to the switch (above) are for reference
only and are marked on the module as indicated on the right.
Key Switch Description
Key switch
Position
Controller Status Memory
Protected
From
Programmer
Changes
Will Accept
Programmer
Stop or Start
Key switch
Transition
Stop Controller is stopped
and disables
Programmer
changes.
Y N From Start or
Memory
Protect: Stops
controller, if
running, and
disables
Programmer
changes
Mem Prt Controller may be
either stopped or
running and
Programmer
changes are
disabled. User
cannot write to
unlocated variables.
Y N From Stop or
Start: Prevents
Programmer
changes,
controller run
status is not
changed
Stop
Mem
Prt
Start
Stop
Mem
Prt
Start
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