ProSoft Technology MVI69-MCM - Manual (Page 147)

MVI69-MCM ♦ CompactLogix or MicroLogix Platform Reference
Modbus Communication Module User Manual
ProSoft Technology, Inc. Page 147 of 167
March 22, 2011
RS-232: Modem Connection (Hardware Handshaking Required)
This type of connection is required between the module and a modem or other
communication device.
The "Use CTS Line" parameter for the port configuration should be set to 'Y' for
most modem applications.
RS-232: Null Modem Connection (Hardware Handshaking)
This type of connection is used when the device connected to the module
requires hardware handshaking (control and monitoring of modem signal lines).