P-NET Datasheet

Communication between individual units of a distributed system of intelligent sensors and actuators, field and central controllers etc, requires a high performance, but economic, fieldbus.

P-NET is the only fieldbus which has large scale implementations on a worldwide basis, and possesses the following characteristics:

Multi master / multi slave network

High Speed

  • Data rate of 76800 baud (cost / performance optimum).
  • Extremely efficient protocol for all
    bus transactions.

Multi-Master Capability

  • Up to 32 masters on 1 bus segment.
  • Simplified arbitration procedure (hardware token passing),
    is 10-100 times more efficient than software arbitration.

Multi-Network Capability

  • Any number of P-NET fieldbusses can be networked using Controller
    Gateways (standard units) without further software expense.

Noise Immunity

  • Electrical isolation between bus and electronics.
  • Screened cable.
  • Check-sum for data security.

Economy

  • Based on the RS485 standard, therefore uses standard components.
  • Single chip 8-bit microprocessors provide necessary performance.
  • 2-wire ring connection up to 1200 m long, dramatically
    reduces wiring costs.
  • Up to 125 devices on 1 bus segment.

High Level Language Support

  • Standard Pascal with extension for multitasking and P-NET, reduce software expenditure.
  • Full support of all functions, including Multi-net capability, by means of the Process-Pascal compiler.

Iplementation Efficiency

Compared to conventional wiring, P-NET
offers demonstrated advantages when applied
to industrial processes, which result in simplification of

  • Planning and installation
  • Maintenance
  • Future expansion of industrial applications

Dignostic Control

The use of intelligent P-NET sensors and actuators offers new diagnostic capabilities.

Apart from the usual measure values and status data, the bus enables a bidirectional exchange of additional information concerning limit values, actuator positioning, fault signals and internal system data. This provides new opportunities for efficient control of maintenance and system security.

P-NET User Organization – IPUO

The International P-NET User Organization has nearly 50 members worldwide. Some of the objects of the organization are:

  • to disseminate global knowledge of P-NET
  • future development of the standard specify conformance test for products
  • exchange info among the members

Specifications

Data transmission

  • Asynchronous transmission
  • Data in NRZ code
  • 76800 bits/sec.
  • 1 start bit, 8 data bit, 1 addr/data bit,
  • 1 stop bit for each byte in the frame
  • Check-sum for data security

Capabilities

  • Up to 125 devices at each bus
  • Multi-master, up to 32 at each bus Multi-network
  • ISO OSI 7 layers reference model
  • High level language support

Data Types

  • Simple: boolean, byte, char, word, integer, longinteger,
    real, longreal, timer.
  • Complex: array, string, record, buffer.

Electrical Specification

  • Bus Structure
    • A physical ring without termination.

  • Medium
    • Shielded twisted pair cable with minimum .22 mm² area conductors and characteristic impedance of 100-120 ohm.

  • Bus length
    • Max 1200 m (EIA RS 485).

  • Integrated transceiver
    • SN 75176A (TI).

  • Installation
    • The bus cable is connected from field device to field device, forming a physical ring.
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