"MELSEC-L Series" Extension System - Mitsubishi Electric

TECHNICAL REPORTS
an extension cable without misreading. Therefore, as
shown in Fig. 5 and Fig. 6, an easily legible universal
font is used for the lettering on the branch and extension
modules. The module type name, I/F usage (OUT:
signal-sending side, IN: signal-receiving side), and
insertion direction of the extension cable are displayed
on the front face of both modules.
5. Features of L Series Extension System
(Easy Troubleshooting)
The functions for diagnosing faults of the bus
communication between modules (communication bus
connected between L series modules) have been improved
so that even if the number of mounted modules
is increased due to system extension, the customer can
quickly perform troubleshooting when a fault occurs.
For fault diagnostics, the CPU module regularly performs
module diagnostic processing for the mounted
modules and an END cover to detect module and system
faults. Figure 7 shows the processing flow, and
Fig. 8 shows the checking of each module and END
cover. This checking identifies the part that caused the
system fault, then the engineering tool allows customers
to easily perform troubleshooting.
(a) Attachment
(b) Detachment
Fig. 4 Connecting the extension cable
Fig. 5 Appearance of a branch module and an extension
module
Fig. 7 Flow of module diagnostic processing
The insertion direction display
prevents reverse connection
of the extension . cable.
Fig. 6 Insertion direction display of an extension cable
Fig. 8 Collation of each module and END cover
(1) Fault diagnosis of bus communications between
modules
If the bus communication signal between modules
is faulty, the CPU module cannot check the modules
and the END cover containing information on the
mounted modules is read out from the bus between
modules so that the processing is terminated.
(2) Checking of each module
The CPU module checks whether abnormalities of
the mounted modules have occurred (when the I/O
module has a different configuration from that at
power-on, etc.). The CPU module detects the boundary
between the normal module and the faulty module, and
sequentially checks the mounted modules from the
Mitsubishi Electric ADVANCE June 2013 15