Rockwell Automation 1775-KA PLC-3 Communication Adapter Module User Manual - Manual (Page 23)

Installation
Chapter 2
2Ć11
Each mode of operation requires a different communication protocol. The
unpolled mode uses full–duplex protocol (chapter 10) while the polled
mode uses half–duplex protocol (chapter 11). In general, full–duplex
protocol gives faster data throughput but is more difficult to implement;
half–duplex protocol is easier to implement but gives slow data
throughput.
NOTE: In other Data Highway documentation, full–duplex protocol
might be referred to as DFI protocol, and half–duplex protocol might be
referred to as polled–mode protocol.
Hardware Interface
The modem interface is based on EIA RS–232–C and related standards.
This interface should be compatible with most dedicated and dial–up
network RS–232 modems.
Mechanical
The RS–232 connector on the 1775–KA module is a 25–pin male
connector.
Electrical
Input and output levels on the RS–232 connector conform to the
RS–232–C standard. The transmitter has increased capability to drive a
7,000 foot isolated lines. This number depends on baud rate and refers to
only direct wire connections. (Refer to Table 2.C.)