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8 TROUBLESHOOTING
8 TROUBLESHOOTING
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In order to ensure high system reliability, it is important to take precautions before the
system is operated and to quickly and effectively correct problems if they do occur.
This is why it is important to perform off-line testing of the network and checking of the
cables when first starting the system.
Make sure to perform the following checks, which are explained in Chapter 4, "Setup
and Procedures Before Starting the Operation."
1)
Standalone operation check and operational setting of the network module
2)
Offline tests:
Hardware test, Internal self-loopback test, self-loopback test and forward
loop/reverse loop test.
3)
Check the connection of the data link cable.
Network diagnostic loop test (requires optical loop)
Even with this, if an error does occur, it is important to quickly and accurately
understand the nature of the problem. The following are three methods for confirming
the contents of an error.
(1) Network diagnostics to remote master station with GX Developer
(a)
Line monitor (see Section 8.1)
The status of the following four types of networks can be checked by
monitoring the line:
1)
Status of the entire network: Host information
2)
Data link status and parameter status, etc. of each station:
Other station information
3)
Control station information, detailed data link information, etc.:
Network monitor details
4)
Loop switch count, line error, communication error, etc.:
Error history monitor
(b)
Diagnostic tests (see Sections 4.10)
The following four items can be checked or executed through the diagnostic
tests:
1)
Wiring status (IN/OUT, etc.) of the data link cable:
Loop test (required for optical loop)
2)
Setting status of numbers: control station/remote master station
duplication, network numbers and group numbers: Setup confirmation test
3)
The order of stations connected in the direction of the forward loop and
the reverse loop: Station order check test
4)
Setting status of the routing parameters: Communication test
(2) Confirmation by error code: See Section 8.3
When either cyclic transmission or transient transmission using dedicated link
instructions or GX Developer (communication with other stations) was not normally
performed, an error code is stored in the special link register and the system monitor.
The contents of the error can be checked by this error code.
(3) Confirmation by the LED displays on the front of the network
module (see Section 4.2)
With the LED displays, the following errors can be checked: whether the host is
operating or stopped, whether the station acts as a control station or a normal
station, whether the baton pass is being executed, whether data linking is being
executed, whether data is being transmitted/received, and whether any error has
occurred.
MELSEC-Q
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Troubleshooting
