User`s manual

Western Reserve Controls 1782-JDM User’s Manual

PUB 24.0

2.2 How to Change the DeviceNet Baud Rate

1. The baud rate defaults to autobaud. You can change the baud rate in software to a fixed baud rate

using your configuration tool or any command from the Master.

If you change the baud rate, the new baud rate will not become effective until the unit is power cycled

or a Reset command is received from the Master.

2.3 How to Install the Modbus Device Network

1. The communication between the Modbus device(s) and the 1782-JDM is an RS-232 3-wire full-duplex

link or an RS-485 network, using a 2-wire half-duplex differential signal between the devices.

2. Connect an appropriate cable to your Modbus device. See your Modbus device users manual for

details.

3. Connect the other end of the cable to the JDM using the 3-point terminal plug provided. See

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below.

Table 2-2 JDM Serial Port Connection

Pin # RS232

Signal

RS485

Signal

Designator

1 Transmit Signal + SIG+

2 Receive Signal - SIG-

3 Ground Ground GND

4. Turn on power to the Modbus device.

2.4 How to Read Modbus Device Input Data

1. Set up the poll input data field size in your Master’s scan table to be equal to or greater than the

number of bytes required for the largest Modbus message received from your device(s).

2. Set up a Poll Connection (Connection Instance 2) to the 1782-JDM from the Master.

3. Configure the serial port to read input data by setting the appropriate values in the Parameter Data,

described in Section 3.6.

4. Perform a poll function to the JDM. ASCII data will be received from the JDM. The 1

byte of the field

will be a “record number”, which will be incremented by the JDM each time a new record is received

into the specific input port. The 2

byte contains the device or communication status.

5. The response data bytes will be returned in the mapped poll response data field. The data will be in

binary format and will represent the complete Modbus message, less checksum / CRC data and the

leading “:” (colon) (for ASCII mode).

6. The response will include two extra bytes of data. The first byte of the response will be a “record

counter” which is a counter generated by the JDM to mark the message with a sequential count value.