Issue
The Unity help does not state which ports on the 140CPU6xxxx supports the L9_XMIT function block.

Product Line
EcoStruxure Control Expert (formerly known as Unity Pro), Quantum

Environment
Unity Pro v10, 140CPU67160

Resolution
The Unity documentation shows the following statement for the XMIT block.but it does not specify the PLC
type.  The Unity 140CPU6xxxx only has two Modbus ports.

Function Description
The L9_XMIT (transmit) function block sends Modbus messages from a master PLC to multiple slave PLCs or
sends ASCII character strings from the PLC's Modbus slave port #0, port#1, or port#2 to ASCII printers and
terminals. L9_XMIT sends these messages over telephone dial up modems, radio modems, or simply direct
connection.

The L9_XMIT will only work with Modbus port 1 on the 140CPU6xxxx.