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MELSEC-Q
3 SPECIFICATIONS
(8) Diagnostic function
The diagnostic function is used to check the network's line status and the module
setting status.
The diagnostic function consists mainly of following two types of tests:
• Offline tests
• Online tests
POINT
Execute the online tests when the network module is communicating (T.PASS LED
is on). An error occurs if any of the online tests is executed from a station that has
been disconnected from the data link.
1) Offline tests
The network module's hardware and the data link cable wiring can be
checked at the system startup by setting the network module or GX
Developer to the test mode.
Item Description
Optical loop
system
Coaxial bus
system
Reference
section
Self-loopback test
Checks hardware including the send/receive circuits and the
cables of the transmission system of an individual network
module.
Section 4.7.1
Internal self-loopback test
Checks hardware including the send/receive circuits of the
transmission system of an individual network module.
Section 4.7.2
Hardware test Checks hardware inside the network module.
Section 4.7.3
Forward loop/reverse loop
test
Checks the wiring status of the forward and reverse loops in
the status in which all the stations are connected. (Remote
master station only)
Section 4.9.2
2) Online tests
The status of a line and other items can be easily checked with GX
Developer.
If an error occurs while the system is in operation, the diagnostics
listed below can be executed while remaining in the online status.
Item Description
Optical loop
system
Coaxial bus
system
Data link status
(cyclic transmission or
transient transmission)
Reference
section
Loop test Checks the line status.
Pause Section 4.10.1
Setup confirmation test
Checks for duplicate control stations
and station numbers.
Pause Section 4.10.2
Station order check test
Checks the order of stations connected
in the directions of the forward and
reverse loop.
Pause Section 4.10.3
Communication test
Checks whether or not the transient
transmission can be performed
normally.
It also checks the routing parameter
settings.
Continue Section 4.10.4