Building a low cost deterministic industrial Ethernet system

Nicholas Sargologos, John Ralston, and Iain Davidson

February 15, 2011

Nicholas Sargologos, John Ralston, and Iain DavidsonFebruary 15, 2011

(In this Product How-To design article, Freescale engineers describe how to use the company’s new MPC8309 and MPC8306/S processors to implement low cost deterministic Ethernet designs based on 802.22 and IEEE 1588.)

Enhanced network connectivity mechanisms, developed through the cooperation of related standards groups, have given Ethernet (802.3) the robust qualities required to operate effectively in operational and safety-critical environments.

As a result, manufacturing environments and building automation systems are rapidly adopting Ethernet in compliment with, or as a replacement for, the various fieldbus technologies traditionally used in these environments.

In a typical building or factory network, there may be a number of network domains, each with varying degrees of timing and safety constraints. These may range from the management and operation environments, where standard IT equipment is utilized over Ethernet, to industrial Ethernet-based and fieldbus networks operating in manufacturing or safety critical environments.

More recently, enhanced mechanisms developed by industry standards groups, such as IEEE 1588, have given Ethernet the deterministic qualities needed to function in operational and safety-critical environments.

As a result, factory networks and building automation systems are adopting Ethernet to compliment, and in some cases to replace, various fieldbus technologies currently in use.

To support such a diverse protocol domain, where both fieldbus and Ethernet co-exist, requires a versatile, cost-effective communication processor capable of supporting a diverse range of interconnects and low-level protocol processing.

To address the need for enhanced connectivity between the diverse network domains in the modern industrial market, Freescale Semiconductor has launched the MPC8309 (Figure 1 below) and MPC8306/S embedded processors.

 

Figure 1: MPC8309 Block Diagram

The new processors extend the MPC830x PowerQUICC II Pro processor portfolio into the entry-level industrial and networking applications, with DDR2, 10/100 Ethernet and IEEE 1588 support, PCI 2.3 (available on MPC8309 only), USB2.0, CAN and enhanced interfaces to support both legacy and emerging protocols used in the industrial networking market.

Building a factory network

As shown in Figure 2 below, a typical factory network may consist of a number of domains, each with varying degrees of timing or safety constraints.

These range from management systems, where standard IT equipment is used over traditional Ethernet, to industrial Ethernet-based networks being deployed in plant or manufacturing environments, as well as serial-based fieldbus networks.

In the control and field domains, there are a range of nodes and network connectivity options deployed to provide safety, supervisory, process and logic control over the field equipment.

In order to connect standard Ethernet-based management systems to the production floor, where networked controllers are typically communicating with one another using industrial protocols such as PROFIBUS, CANopen or DeviceNET, some type of bridging solution is required. This is represented in Figure 2 below as a “Converter”. This diverse protocol domain, where both fieldbus and Ethernet co-exist, is a prime opportunity for the application of an SoC design.

 

Figure 2: Typical Factory Automation Network (To view larger image, click here)                          

The integration of a high-performance, power-efficient processor core, together with an optimized blend of interconnect and low-level protocol processing capabilities, can deliver the platform flexibility needed to support the broad spectrum of Industrial processing nodes used today in factory automation applications, including  programmable logic controllers, process automation controllers, intelligent I/O, operator interface terminals, drives and bar-code & ID systems.

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