65-2646XL-05-04 M2A Transmitter Operator’s Manual
Chapter 8: RS-485 Modbus Output
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Using the M2A in a 4-wire Modbus System
Although the M2A is a 2-wire Modbus RTU device, it can be used with a 4-wire Modbus
controller if the system wiring is modified as follows:
• Connect the controller’s TxD0 and RxD0 wires together and use this connection as the 2-wire
Modbus D0 signal.
• Connect the controller’s TxD1 and RxD1 wires together and use this connection as the 2-wire
Modbus D1 signal.
• Connect these D0 and D1 signals and the common wire from the controller to the 2-wire
Modbus Network of M2As.
Modbus Mode
Modbus Mode allows you to configure various parameters relating to the Modbus setup of the
M2A. Modbus Mode includes a 5-minute time-out feature. If you do not press a control button for
5 minutes, the M2A automatically returns to normal operation.
NOTE:
If the M2A returns to normal operation because of a time-out, it enters a warm-up
period just as it does when it is first turned on.
1. While in normal operation, simultaneously press and hold the DOWN/NO and ENTER
buttons for 5 seconds to enter Modbus Mode. Release the buttons when the following screen
appears.
2. To exit Modbus Mode, press and release the DOWN/NO button. The M2A will return to
normal operation.
To continue in Modbus Mode, press and release the UP/YES button. The current
ENABLED/DISABLED setting will appear.
3. If you want to change the currently displayed parameter, use the UP/YES and DOWN/NO
buttons to adjust it to the desired setting, then press ENTER to continue to the next parameter.
If the currently displayed parameter setting is OK, press the ENTER button to proceed to
the next parameter.
Table 9 lists the M2A Modbus Mode parameters you can set. Table 9 also lists the factory
set value for each parameter.
Set Up
Modbus?
