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GFK-1004B
Appendix A Glossary
Responding Station A station which generates a message in response to a command
that was directed to the station.
Round–Trip Propagation Time Twice the time required for a bit to travel between the
two most distant nodes in a bus network.
NOTE: In a network using carrier sense, each frame must be long enough so that a
collision or jam signal may be detected by the transmitting node while this frame is
being transmitted. Its minimum length is therefore determined by the round–trip
propagation time.
Router A device similar to a bridge that allows access to multiple LANs. (Also known as
a gateway in Internet terminology.)
Server A network node that provides specific services to other network nodes (clients).
(See also Client.)
EXAMPLE: File server, print server, mail server.
Service Request Transfer Protocol (SRTP) A proprietary protocol that encodes Series
90 “Service Requests”, the native language of the Series 90 PLC CPUs, to provide
general purpose communications with a Series 90 PLC. SRTP is presently available
over 802.3/Ethernet networks. SRTP is also used by Logicmaster 90 to communicate
over an Ethernet network.
Signal Quality Error (SQE) An indication from the MAU (transceiver) to the Ethernet
Interface to indicate any of three conditions: 1) improper signals received from the
medium, 2) collision detected, or 3) SQE message test.
Slot Time ( in a CSMA/CD network) Minimum bitrate–dependent unit of time which, in
case of collision, is used to determine the delay after which network nodes may attempt
to retransmit. [Slot time for all IEEE 802.3 10 Mbps implementations is 51.2 µsec (512 bit
times)].
Soft Switches Basic system information set up by the Logicmaster 90 Configurator and
transferred to the LAN Interface upon powerup or restart.
Station A computer, PLC, or other device that connects to one or more networks. (See
also Node.)
Station Address Each node on an Ethernet network must have a unique MAC address
which is different from all other nodes on the network. This is a 12–hexadecimal
digit MAC address. (See also MAC Address.)
Station Manager A part of the basic Ethernet Interface communications software that
executes as a background activity on the Ethernet Interface. The Station Manager
provides interactive supervisory access to the Ethernet Interface. The Station
Manager may be accessed locally via the serial port, or remotely over the LAN.
Tally Counters kept by the LAN Interface to indicate load and performance information.
Topology The pattern formed by the physical medium interconnecting the nodes of a
network.
Transceiver See Medium Attachment Unit (MAU).
Transceiver Cable See Attachment Unit Interface (AUI).
Transmission Path Delay The time required for a bit to travel between the two most
distant network nodes in a bus network.