Specifications

80 Rockwell Automation Publication AG-SG001G-EN-P - April 2015
Glossary
Parallel Port An electrical connection on a computer capable of transmitting or receiving two
or more bits of data at one time. The communication port to which such devices
as parallel printers can be attached.
Point-to-multipoint A network where connections exist between one master station and multiple
remote stations.
Point-to-point A network where a connection is made between two and only two terminal
installations.
Poll When the master station sends a message to a remote station that allows the
remote station an opportunity to return a response to the master or another
remote station. In this manual, when the master polls a remote station, it is not
initiating a read request.
Polling Cycle The order and frequency in which network nodes in a poll list are polled.
Poll List A list of nodes or stations on a network to be polled on a regular and repeated
basis.
Protocol A set of conventions governing the format and timing of data transmission
between communication devices, including handshaking, error detection, and
error recovery.
Private Leased Line Network (PLL) A dedicated voice-band telephone line between two or more locations primarily
used for data transmission.
Public-switched Telephone Network
(PSTN)
The standard dial-up telephone network originally used for voice
communication.
RS-232 An EIA electrical connection standard, most often used as a standard interface
for serial binary communication between data terminal equipment and data
communication equipment.
RTS Request To Send. A request from the DTE module to the modem to prepare to
transmit. In response, the modem typically sends out a data carrier signal and
turns on CTS.
RTU Remote Terminal Unit. See remote station.
RXD Received Data. A serialized data input to a receiving device.
Remote Station A device (programmable controller with I/O modules) that is located in a remote
site away from the master station and that controls I/O points at the remote site.
A remote station accepts commands from and can send data (if capable) to a
master station via a telemetry network.
SCADA Supervisory Control and Data Acquisition