Status Indicators
The status indicator LEDs on the CPU front panels have specific functions which can help in
programming and troubleshooting.
Mode Switch Functions
The mode switch on the DL240, DL250–1 and DL260 CPUs provides positions for
enabling and disabling program changes in the CPU. Unless the mode switch is in the TERM
position, RUN and STOP mode changes will not be allowed by any interface device,
(handheld programmer,
Direct
SOFT programing package or operator interface). Programs
may be viewed or monitored but no changes may be made. If the switch is in the TERM
position and no program password is in effect, all operating modes as well as program access
will be allowed through the connected programming or monitoring device.
There are two ways to change the CPU mode.
• 1. Use the CPU mode switch to select the operating mode.
• 2. Place the CPU mode switch in the TERM position and use a programming device to change
operating modes. In this position, you can change between Run and Program modes.
NOTE:
If the CPU is switched to the RUN Mode without a program in the PLC, the PLC will produce a
FATAL ERROR which can be cleared by cycling the power to the PLC.
DL205 User Manual, 4th Edition, Rev. B
3–12
Chapter 3: CPU Specifications and Operations
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A
B
C
D
Mode Switch Position
CPU Action
RUN (Run Program)
CPU is forced into the RUN mode if no errors are encountered. No
changes are allowed by the attached programming/monitoring device.
TERM (Terminal)
RUN, PROGRAM and the TEST modes are available. Mode and program
changes are allowed by the programming/monitoring device.
STOP (DL250–1 and DL260 only Stop Program)
CPU is forced into the STOP mode. No changes are allowed by the
programming/monitoring device.
Indicator
Status
Meaning
PWR
ON
Power good
OFF
Power failure
RUN
ON
CPU is in Run Mode
OFF
CPU is in Stop or program Mode
Blinking
CPU is in Firmware Upgrade Mode
CPU
ON
CPU self diagnostics error
OFF
CPU self diagnostics good
BATT
ON
Low battery voltage (only with System
Memory bit B7633.12 set)
OFF
CPU battery voltage is good or disabled