Run Led (A68Adn) Is Flashing; Run Led (A68Adn) Is Off; Digital Output Value Cannot Be Read - Mitsubishi Electric MELSEC A Series Manual

6. TROUBLESHOOTING
6.2 Troubleshooting
6.2.1

RUN LED (A68ADN) is flashing

6.2.2

RUN LED (A68ADN) is OFF

6.2.3

Digital output value cannot be read

This section deals with troubleshooting related to the A68ADN. For troubleshooting
related to the PC CPU, see the appropriate PC CPU User's Manual.
Check Point
Data which disables write or read is written to the
A68ADN.
Check Point
Are the TEST terminals open?
Is the X2 signal (watchdog timer error) ON?
Check Point
Is the RUN LED (A68ADN) either flashing o
OFF?
Is the ERROR LED (PC CPU) ON?
Is the RUN LED (PC CPU) either flashing or
OFF?
Have conditions to execute a FROM instructio
been met?
Is the buffer memory address designated by a
FROM instruction the address for the digital
output value from the channel to be read?
Is the channel designated by a FROM instruction
A-D conversion enabled?
Is A-D conversion completed for the channel
designated by a FROM instruction?
Is the analog input signal cable broken or
disconnected
Disconnect the analog input cable from the
A68ADN, and apply a test voltage (using either
stabilized power supply or a battery) to measure
digital output value.
Check the error code table (see Section 6.1) for
the cause, and correct the sequence program.
After offset/gain setting, open the TEST terminals.
Reset the PC CPU.
If the RUN LED is not ON even after the PC CPU
is reset, the hardware is faulty.
Consult the nearest Mitsubishi representative.
See Section 6.2.1 or 6.2.2.
See the appropriate PC CPU User's Manual.
See the appropriate PC CPU User's Manual.
Monitor the conditions with a peripheral device
(like a GPP) to see if they have been met.
Check the sequence program.
Read buffer memory address 0 to check th
enable/disable setting for the channel in question.
Read buffer memory address 19 to see whether
or not the A-D conversion-completion flag is set.
Find the defect, using both visual inspection and a
continuity check.
If the digital output value is correct, it means that
the module is influenced by external noise, etc
Check cable connections and grounding.
6 − 2
MELSEC-A
Corrective Action
Corrective Action
Corrective Action