Connecting Modbus Slave Devices To Serial Ports - Allen-Bradley AADvance Manual

Chapter 5 Install the AADvance System
98
Terminal Function Description (4-wire)
TRX_A Receive data A (inverting)
TRX_B Receive data B (non-inverting)
0V Instrument ground (signal ground)
TX_B Transmit data B (non-inverting)
TX_A Transmit data A (inverting)
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The line functions shown in the table ("receive" and "transmit") are with
respect to the processor base unit.
NOTE To connect to the external communication link you should
terminate the receive end of the twisted pairs with a 120 Ω
resistor in series with a 68nF capacitor at the receiver ends.

Connecting MODBUS Slave Devices to Serial Ports

You can use a full duplex or a half-duplex connection for a MODBUS Slave
device on a serial port.
Rockwell Automation Publication ICSTT-RM448J-EN-P - April 2018
1
Function Description (2-wire)
Transmit/receive data A (inverting)
Transmit/receive data B (non-inverting)
Instrument ground
not used
not used
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