Knowledge Base / Protocols / DeviceNet

1782-JDM Frequently Asked Questions

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 1.  1.       Where is the 1782-JDMx gateway User’s Manual located?

The WRC 1782-JDMx product User’s Manuals are available from our web site Support -> Technical Data

2.       What are the 1782-JDMx gateways and why should I consider purchasing one for my

      DeviceNet network?

The 1782-JDMx gateways are communication adapter devices that provide you with a flexible DeviceNet-to-ModBus interface for ModBus-capable devices. .

 The JDMx models allow you to easily and conveniently connect and integrate peripheral products with either RS-232, RS-485 or RS-422 serial ports into a DeviceNet system, enabling you to select just the right peripheral device for your application without limiting your selection to DeviceNet-cable devices only.


3.       How can I change the DeviceNet MAC ID of my 1782-JDMx?

The address of the 1782-JDMx will come preset from the factory for address 63. You may change the address using the bank of 6 DIP switches on the unit: they can be set to any address from 0 to 63 in binary (111111=address 63). The MACID or address will not change if the switches are moved while the device is powered; power must be removed and reapplied when a new switch setting and MAC ID are desired or a device reset command must be issued.


4.       What electrical connections are required for a 1782-JDMx gateway?

DeviceNet Cable Connection:

1, 5-pin pluggable header (male, Phoenix Contact MSTBA 2.5/5-G-5.08/AU or equivalent)


Serial Cable Connection: For RS-232 & RS-485

1, 3-pin pluggable header (male, Phoenix Contact MSTBA 2.5/3-G-5.08/AU or equivalent)


Serial Cable Connection: For RS-422

1, 5-pin pluggable header (male, Phoenix Contact MSTBA 2.5/5-G-5.08/AU or equivalent)


5.       How do I begin to use a 1782-JDMx gateway?

You can begin to use a 1782-JDMx gateway by following the User’s Manual Quick Start instructions.


6.       What are the LEDs on the 1782-JDMx indicating?

There are two sets of LEDs on the unit. The two green LEDs next to the serial connector are used as indicators for the serial communication receive and transmit ports. The other two bi-color LEDs are used to indicate the DeviceNet module (MS) and network (NS) status. For troubleshooting or further information on status definitions corresponding to LED actions see LED Operation in the 1782-JDMx User’s Manual.


7.       On what DIN rail can I mount the 1782-JDMx?

The 1782-JDMx can be mounted on DIN rail mount, EN 50022 (WRC50022).


8.       What are some common applications for the 1782-JDMx gateway?

A 1782-JDMx gateway provides DeviceNet communications for weigh scales, bar code readers and scanners, display panels, robots, drives, operator stations / HMI, magnetic code readers and other ASCII serial devices.


9.         Are the 1782-JDMx gateways designed to plug-n-play?

Yes, the 1782-JDMx gateways are designed to plug-n-play using our factory default settings: serial framing of 7N2, serial baud rate of 9600, max number of receive and transmit characters set to 48, Modbus mode set to ASCII, etc. The full list of default settings can be found under Default Settings in the User’s Manual.

If you wish to change any parameters from their default settings you will need to use a DeviceNet software configuration tool. Many of these tools have EDS readers, which make the editing process easier.


10.Does a 1782-JDMx gateway provide electrical isolation?

Yes, a 1782-JDMx gateway provides 1000V network electrical isolation.


11.   What are the currently available 1782-JDMx gateway models?

1782-JDM-1: Isolated RS232 Interface

1782-JDM-2: Isolated RS485 Interface

1782-JDM-4: Isolated RS422 Interface


12.   On what DeviceNet baud rates does the 1782-JDMx communicate?

The unit works with 125k, 250k or 500k baudrates. It is default set to autobaud on DeviceNet. A fixed baudrate of 125k, 250k or 500k may also be assigned with a software configuration tool.


13.   On what baud rates does the serial port communicate?

The serial port on the 1782-JDMx will communicate on baudrates of: 1200, 2400, 4800, 9600, 19.2k, or 38.4k baud.


14.   How do I connect a 1782-JDMx gateway to a serial port device?

You connect the JDMx to a serial port Modbus device with the Phoenix connectors on the unit, which are labeled for which signal goes in each port of the connector. For RS-232 or RS-485 communications the signal/pin assignments are as follows:



Pin #

RS232 Signal

RS485 Signal




Signal -




Signal +







For RS-422 communications the signal/pin assignments are as follows:


Pin #






Transmit -



Transmit +






Receive -



Receive +


15.   How is the Master Handshake mode different from the Hardware handshake RTS/CTS?

Master Handshake mode is a data control mechanism between the DeviceNet master and the 1782-JDMx (after the JDMx receives data from serial device), communicated in IO message. The 1782-JDMx indicates new data arrival and waits for Master to issue a new record number, to be used with new data. The hardware handshaking via RTS/CTS (which is not supported in the 1782-JDMx) requires two additional signal lines on the serial side and it controls the data before it is received.


16.   When should I turn Pad Mode ON? Or what configuration parameter should I check when the scanner cannot stay connected to the 1782-JDMx due to an IO size error?

If the DeviceNet scanner or the master device needs to be pre-configured with an input (produce) size before making a connection, or if the serial device will be sending variable data size strings, you will need to turn the PAD Mode ON. This parameter should be checked if the 1782-JDMx will not stay connected due to an IO size error.


17.   What should my master device logic be doing to see if new data is present in a poll message?

The Master program logic should be looking at the Receive Record Number and comparing it with the last stored record number to monitor new data arrival in Immediate (Non-Handshake) Mode. In the Master Handshake mode, the program should be looking at the New Data bit in status and if detected, should supply the new record number and wait for the 1782-JDMx to produce data along with that record number.


18.   What does the 1782-JDMx gateway require for power?

The 1782-JDMx receives all necessary power from the DeviceNet network cable. This should be between 11 and 25 Vdc.  It consumes about 2 watts of power maximum.


19.   How do I access the serial ASCII data from a 1782-JDMx gateway?

When configuring your PLC, you have the option to memory map the ASCII data from the 1782-JDMx to a location on your PC. The ASCII data can be found at this location.


20.   When do I need to use an EDS (electronic data sheet) file for a 1782-JDMx gateway?

An EDS file is not necessary, but it makes configuring the 1782-JDMx (changing baud rate, framing, etc.) far easier than if you were to try to change the device parameters by editing the attributes of certain class objects and instances without the aid of a configuration tool. There are many software configuration tools available with EDS readers that can be used to set up the device.


21.   What is the proper cable to use for a 1782-JDMx gateway serial connection?

The proper cable selection depends upon which gateway model is used, the serial communication baud rate desired and the total cable length.  Cable selection guidelines:


1782-JDM-1: RS232 3-wire shielded

1782-JDC-2: RS485 3-wire shielded

1782-JDC-4: RS485/RS422 3-wire (RS485) shielded or 5-wire (RS422) shielded


22.   Where can I purchase the proper cable for a 1782-JDMx gateway serial connection?

You can purchase the proper cable from many suppliers and fitted with the connectors required for the gateway model and serial device being used.