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Appendix A Glossary
Remote Station Station located elsewhere on the network. (See also “Local Station”)
Repeater In a Local Area Network, a device that amplifies and regenerates signals to
extend the range of transmission between network nodes or to interconnect two or
more segments.
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 or
CIMPLICITY Control 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.)
Subnet Mask The subnet mask is a mechanism to logically divide a large network into
smaller subnets according to your local assignment of IP addresses to nodes on the
network. Nodes on the network which have their IP addresses alike for the bits
specified in the subnet mask can talk to each other directly; nodes whose IP
addresses are not alike in these same bits must talk indirectly, via an intermediate
gateway or router.