ABB INNPM12 Control Network, Cnet

ABB INNPM12  Control Network, Cnet

DESCRIPTION

Control Network, Cnet, is a high-speed data communication  highway between nodes in the Symphony™ Enterprise Management and Control System. Cnet provides a data path  among Harmony control units (HCU), human system interfaces (HSI), and computers. High system reliability and  availability are key characteristics of this mission-critical  communication network. Reliability is bolstered by redundant hardware and communication media in a way that the  backup automatically takes over in the event of a fault in the  primary. Extensive use of error checking and message  acknowledgment assures accurate communication of critical  process data.

Cnet uses exception reporting to increase the effective bandwidth of the communication network. This method offers the  user the flexibility of managing the flow of process data and  ultimately the process. Data is transmitted only when it has  changed by an amount which can be user selected, or when a  predetermined time-out period is exceeded. The system provides default values for these parameters, but the user can  customize them to meet the specific needs of the process  under control.

Features and Benefits

■ Fast plant-wide communication network: Cnet provides fast  response time to insure timely  information exchange.

■ Efficient data transfer: Message  packing and multiple addressing increase data handling  efficiency and throughput. 

■ Plant-wide time synchronization: Time synchronization of Cnet  nodes throughout the entire  control process insures accurate  data time-stamping. 

■ Independent node communication: Each Cnet node operates  independently of other nodes.  Requires no traffic directors;  each node is its own  communication manager. 

■ Accurate data exchange: Multiple self-check features including  positive message acknowledgment, cyclic redundancy checks  (CRC), and checksums insure  data integrity. 

■ Automatic communications  recovery: Rack communication  modules provide localized startup/shutdown on power failure  without operator intervention.  Each type of interface supports  redundancy

Control Network

Cnet is a unidirectional, high speed serial data network that operates at a 10-megahertz or twomegahertz communication rate. It supports a central network with up to 250 system node connections. Multiple satellite networks can link to the central network. Each satellite network supports  up to 250 system node connections. Interfacing a maximum number of satellite networks gives a  system capacity of over 62,000 nodes.

On the central network, a node can be a bridge to a satellite network, a Harmony control unit, a  human system interface, or a computer, each connected through a Cnet communication interface.  On a satellite network, a node can be a bridge to the central network, a Harmony control unit, a  human system interface, or a computer.

Harmony Control Unit

The Harmony control unit is the fundamental control node of the Symphony system. It connects to  Cnet through a Cnet-to-HCU interface. The HCU cabinet contains the Harmony controllers and  input/output devices. The actual process control and management takes place at this level. HCU  connection to Cnet enables Harmony controllers to:

■ Communicate field input values and states for process monitoring and control. 

■ Communicate configuration parameters that determine the operation of functions such as  alarming, trending, and logging on a human system interface. 

■ Receive control instructions from a human system interface to adjust process field outputs. 

■ Provide feedback to plant personnel of actual output changes.

INIIR01 Remote Interface

The INIIR01 Remote Interface consists of the INNIS01 Network Interface Module and the INIIT12  Remote Transfer Module . This interface is a node on a central network that can communicate to an interface node on a remote satellite network. In this arrangement, two interfaces are  required: one for the central network, and the other for the satellite network. Bidirectional communication from the central network to the remote satellite network is through standard RS-232-C  ports.

The remote interface supports hardware redundancy. Redundancy requires a full set of duplicate  modules (two INNIS01 modules and two INIIT12 modules on each network). The secondary  INIIT12 module continuously monitors the primary over dedicated Controlway. A failover occurs  when the secondary module detects a primary module failure. When this happens, the secondary  interface takes over and the primary interface is taken offline.

INIIL02 Local Interface

The INIIL02 Local Interface consists of two INNIS01 Network Interface modules and the INIIT03  Local Transfer Module (Fig. 3). This interface acts as a bridge between two local Cnets. One of the  INNIS01 modules operates on the central network side and the other operates on the satellite network side. Bidirectional communication from the central network to the local satellite network is  through cable connection to the NTCL01 termination unit. The maximum distance between  termination units on the two communication networks is 45.8 meters (150 feet).