Industrial Standards
IEEE 1588
Incorporating Ethernet technologies into industrial applications can bring many benefits—for example, high speed, low cost, smooth interoperability. But you also face challenges with systems that have hard, real-time requirements. For example, you may need to synchronize distributed motion controllers, or simultaneously feed back and react to measurements from many sensors in widespread locations. The IEEE 1588 standard provides a way to synchronize devices on a network with submicrosecond precision.
Known as the “Precision Clock Synchronization Protocol for Networked Measurement and Control Systems (or, PTP for precision time protocol),” the IEEE 1588 standard makes it possible for many spatially distributed real-time clocks to be synchronized through a package-compatible network, such as an Ethernet network. One master and many slave clocks are continuously synchronized across the network, ensuring that timing drift is eliminated and all devices use the same time base. Ideal for user-administered, distributed systems, the standard minimizes use of network bandwidth and lowers processing overhead.
IEEE 1588 works well in scenarios where the master and slave clock are connected by a single point-to-point connection. However, many Ethernet systems use switches, which means that this point-to-point connection is not possible. An Ethernet switch normally introduces a high degree of variability into the time taken to deliver a packet, especially under high load conditions. This, combined with the lack of symmetry between the time it takes for packets to travel in both directions, can degrade the reliability of a 1588-based system to unacceptable levels.
The solution to this problem is to use IEEE 1588 boundary clocks in the switches. With a boundary clock, which essentially becomes the master clock, you have point-to-point connections across the network. The issues created by normal switches no longer occur as the switch now offers a predictable packet-forwarding mechanism.
For more information on an Altera based IEEE1588 based product offering please visit our industrial partners web page.
IEC 61131-3
IEC 61131 is an international standard first published in December 1993 by the IEC. Part 3 of IEC 61131 deals with programming languages; it defines ways to manage control processing and two graphical and two textual PLC programming language standards:
- Ladder diagram (LD), graphical
- Function block diagram (FBD), graphical
- Structured text (ST), textual
- Instruction list (IL), textual
- Sequential function chart (SFC), for sequential and parallel control processing
This programming language standard was developed for Programmable Logic Controllers (PLCs) and has now been widely adopted in the industrial world. It is an open standard, regulated by the vendor and product-independent worldwide association PLCopen, http://www.plcopen.org/.
For more information on an Altera based IEC 61131-3 based product offering, please visit our industrial partners web page.
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