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MJ-X Communications Module
6.6.1 Using LEDs to Help Diagnose Communications Problems
The communications module's Txd and Rxd LEDs can be useful indicators to help isolate system communications
problems. The LEDs are directly activated by the transmit and receive signals and provide an immediate indication
of line activity. If the Rxd LED is not illuminated, then no receive signal activity is being detected at the
communications module Terminal Block connector.
If the Txd LED is not illuminated but the Rxd LED is illuminated, then the communications module is not
responding to communication attempts. This may occur for a variety of reasons, including 1) the communications
module and/or MJ-X Control Panel has not been configured properly, and 2) the unit is not being addressed.
If the Comm LED is not illuminated, then the communications module is not being addressed.
If the Rxd LED is illuminated but the Comm LED is not illuminated, this indicates that the module is receiving the
transmission but does not detect its address in the message. Recheck the communications address, because it may
not be set properly.
Verify that the MJ-X communications configuration items have been set to match the system settings. (See section
6.5, Communications Module Configuration.)
6.6.2 Using MJXplorer to Troubleshoot Communications Problems
The MJXplorer software is a menu-driven application program that allows interfacing to the MJ-X Communications
Module. Since the current version of MJXplorer does not support networking, only one MJ-X unit may be
connected at a time. For connecting an MJ-X Fiber Optic Communications Module to MJXplorer, the Fiber Optic
auto repeat function must be disabled (since MJXplorer gets confused if it receives back its own transmissions.) See
section 3.1.1 (Version 2) or section 4.2.1 (Version 1) for setting the Fiber Optic board jumpers.
A fiber optic communications module requires a Fiber Optic to RS-232 driver/receiver in order to perform these
tests. The driver/receiver is an optical to electrical signal converter with an ST connector interface and an RS-232
interface. Connect the optical side to the fiber optic communications module via ST fiber optic patch cords. Connect
the RS-232 interface to the personal computer, Figure 6-7.
Use MJXplorer to help pinpoint communications problems in a system. MJXplorer permits testing of the
MJ-X communications functions independent of other system components.
Once the physical connections are complete, select the "2200NOA" protocol from the MJ-X front panel. In
addition, set the Comm Parity and Comm Baud to match the MJXplorer settings. Use MJXplorer to verify that data
can be retrieved from as well as written to the MJ-X Control Panel.
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