Detcon MCX-32-N4X - Manual (Page 46)

Model MCX-32
Model MCX-32 Instruction Manual Rev.2.3 Page 40 of 49
9.0 Troubleshooting
If the MCX-32 display does not come on when power is applied to the unit, check the Power Supply Voltage
for an output of 24VDC. Also check the Interface PCA, J5 PWR to GND for 24VDC out to the monitor.
The MCX-32 provides features to aid in troubleshooting communication problems in the sensor network.
Problems with Modbus™ communications can be identified with the aid of the System Configuration’s
Modbus™ Utilities (Section 6.3.7 Modbus Utilities Screen). From this menu the status of each device can be
viewed via the Modbus™ Diagnostic screen. The Modbus Diagnostics screen displays the status, number of
errors, and the total error time of each channel or device connected on the Modbus™. This information can be
used to determine if the communication problem is with one device, several devices, or the whole RS-485
Network.
NOTE: AO-4 and RL-4 modules are addressed at higher locations (80-8Eh for RL-4 modules,
and A0-AFh for AO-4 modules) and appear when their respective menu buttons are selected.
DA-4 and DI-4 modules, although addressed at higher locations (40-4Fh), are displayed at the
corresponding addresses of their channels.
(i.e. a DA-4 Module addressed at 42h will
correspond to channels 9, 10, 11, and 12 respectively. Refer to Table 1 DA-4/DI-4 Modbus
Addresses).
If the controller is working properly, and only one or two devices are having communication problems, those
devices should be suspect, and replaced with a known good devices for test purposes. If the problem clears, do
not re-install the original devices until it can be determined that they are not the cause.
NOTE: When trouble shooting any device that may be on the RS-485 Modbus™ Network,
always refer to that devices manual for proper setup of the device on the network, and refer to
that manual’s troubleshooting section for possible remedies for communication problems.
If the problem is the inability to communicate with 2 or more devices, the issue may be the RS-485 network.
The first step in trouble shooting an RS-485 network is to look at the network wiring scheme. The MCX-32
controller utilizes two separate RS-485 ports for device communication. The wiring scheme for each port
must adhere to RS-485 specifications (i.e. length of wire, proper termination, the use of repeaters, etc.). It is
critical that any device connected to the controller is connected to the appropriate port. Many communication
problems can be caused by connecting the device to the wrong port. Refer to Section 7.0 Controller Setup for
the port assignment of sensors and modules used by the controller.
Insure that the cabling used is the correct type for RS-485 communication. RS-485 wiring with power should
consist of a two conductor, shielded twisted pair for RS-485 and two conductor power (General Cable
Commodore p/n ZO16P0022189 is recommended). Check all cable connections for security, open, shorted, or
improper wiring.
When it has been determined that the wiring scheme is correct and the cabling is correct, the next step in
finding a communication problem is check communications between the MCX-32 and each individual sensor.
On the MCX-32 controller, before troubleshooting an RS-485 problem it should be determined if the
Communications error is on Port 1, Port 2, or both. This procedure will work for both Port 1 and Port 2 of the
RS-485 Modbus™.
NOTE: The Controller utilizes 2 ports.
1. Disconnect the data wires (A & B) from the output terminal blocks of the effected port. This will
remove all external devices from the controller.