GE 90*-30 PLC Series User Manual

Also see for 90-30 PLC: Installation and Hardware Manual

Contents

D-4 Series 90™-30 PLC LONWORKS® Bus Interface Module User's Manual – June 1997 GFK-1322ADChannel Status Bits The Channel Status bits comprise bits 17–80 (64 bits) of the statusindication area. These bits consist of an error bit and a data transferbit for each of the channels that can be establishedClient A node that requests network services from a server. A client PLCinitiates a communications request. (See also Server.)Collision A condition that results from concurrent transmissions by two ormore nodes on the transmission medium.Collision Domain A single CSMA/CD network. If two or more nodes are within thesame collision domain and both transmit at the same time, a collisionwill occur. Nodes separated by a repeater are within the samecollision domain. Nodes separated by a bridge are within differentcollision domains.Command Dictionary Provides an alphabetical listing of the LAN Interface commands.Command Field That part of a protocol data unit (PDU) that contains commands, asopposed to the address field and information field.Communications Window A part of the PLC scan that provides an opportunity for the LANInterface to read and write PLC memory. The window is executedautomatically once per PLC scan.Connection A logical communication link established between two end pointsand used to transfer information.CSMA/CD See Carrier Sense Multiple Access with Collision Detection.Data Communications Equipment(DCE)Examples: Modems and transceivers. Distinct from DTE, DataTerminal Equipment.Data Link Layer In Open Systems Interconnection architecture, the layer (Layer 2)that provides services to transfer data over a physical link betweenopen systems. Consists of the LLC and MAC sublayers.Data Terminal Equipment Examples: computers, terminals, printers. Distinct from DCE, DataCommunications Equipment.DCS Words See Detailed Channel Status Words.Detailed Channel Status Words Two status words containing detailed information on a single Series90 channel. The DCS words are retrieved using the Retrieve DetailedChannel Status Command.Device Name A character string that identifies a particular communicationdestination at a given network adapter ( for example, the PLC CPUor an SNP gateway).Directory Information Base (DIB) A collection of information used for directory services (like nameresolution). In this document DIB refers to the DDP database whichis actually distributed among all DDP devices instead of in a singlename server. (See also Distributed Directory Protocol (DDP).Distributed Directory Protocol(DDP)The GE proprietary protocol used to provide distributed nameservice on a TCP/IP Ethernet network. The distributed nature ofDDP means that there is no name server.Domain Name System (DNS) The predominant name service protocol used by the Internet. DNS isprimarily used to resolve a name into an IP address.Dotted Decimal The notation for IP, gateway, and name server addresses as well asthe subnet mask. It consists of 4 decimal numbers (0–255) separatedby periods. Example IP address: 3.0.0.1Dynamic Host ConfigurationProtocol (DHCP)A superset of the BOOTP protocol (see BOOTP).