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Tech Corner: SLC Processors

on April 23, 2019

Welcome to our first Tech Corner blog post, where our senior engineers advance our understanding of issues in food and beverage automation. Here, ESE Senior Engineer Tim Steinke shares his expertise on SLC processors.

A Brief History of the SLC Processor

 SLC processors were first introduced in 1989. During these initial offerings, it was very much a “shoebox” style with fixed I/O so you didn’t have the ability to add on. In 1991 SLC 500 processors were introduced as an alternative to the larger “system-based” PLC5. These were “Small Logic Controllers” that offered rack installations with selectable I/O modules. These new processors were much less expensive than the PLC5, had a smaller footprint and came with an evolution of networking options (serial communications, Data Highway (DH485), Data Highway Plus (DH+), Ethernet).

Starting with the SLC 5/03, you could edit a program while online, which was a HUGE development. Prior to this, you had to take the processor out of service to make your change and then do a download. This put the SLC capabilities closer to the PLC5 and opened the door for a larger use of the economical processor. And as technology improved, the memory on the SLC500’s kept improving as well allowing larger systems to be programmed using the smaller SLC processors rather than the PLC5. You can visit this page for additional insight on the history and relationship of the PLC5 and SLC processors.

The SLC Processor’s End of Life

The SLC500 processor has about a 30-year life cycle before issues start to arise. The strength of the Rockwell platform is a testament to the solution, especially given the rapid pace at which technology has evolved. To put in perspective, the introduction of the SLC was initially rolled out on a DOS operating system. Obsolescence is mainly driven by the availability of parts to build new processors and I/O.

The original remote networking options such as Allen Bradley Remote I/O, DeviceNet, Data Highway are harder to maintain than Ethernet which has since the 90s become the industry standard. And as the workforce ages, the older networks are much more difficult to troubleshoot. Newer programmers and technicians haven’t been exposed to these legacy networks and are thus unfamiliar with how to work with them.

If you’re curious to see where your specific parts may be in their product lifestyle, I encourage you to take a look at Rockwell’s product life cycle page, where you can plug in the catalog number and pull up whether that part is.

Alternatives and Replacements for the SLC Processors

There are a number of alternatives for SLC processors which are all dependent on your needs, facility and set up. This is often where an ESE type control system integrator can be helpful. A qualified controls engineer can help develop a system architecture with the future in mind. Rather than upgrading your processes in a piece-meal fashion, looking at the entire system allows the integration to follow a plan. Just like in anything, having a plan allows you to see what you want the result to be. Upgrading without a plan in place can lead to rework and additional costs. Find out more on our Facility Modernization page.

There is not a one-size-fits-all solution for every application, but Rockwell offers a wide range of products that can be used independently or collectively. However, a reminder that it is not recommended to simply replace a part with a new one. There needs to be a plan in place that looks to the future. I’ve listed several options below:

  • CompactLogix 5380 Controllers
    • Ideal for Small to Mid-Size applications
    • Embedded Ethernet Ports for Communication (up to 1 GB)
    • USB port for alternative connection for programming
  • CompactLogix 5480 Controllers
    • Ideal for Medium to Large applications
    • Embedded Ethernet Ports for Communication (up to 1 GB)
    • USB port for alternative connection for programming
    • Includes Windows 10 Internet of Things Enterprise
      • Separate processor from Controller operations
      • Reduces the footprint for data and SCADA needs
      • Increases data exchange rates with other servers and systems
    • Expanded security
  • ControlLogix L7X Controllers
    • Solution for larger systems
    • Possible to combine several existing SLC processors into a single processor
    • Can put multiple processors in a single rack to economize on communications between them using the rack backplane – i.e. no load on the networking.
    • Supports several network options including legacy networks previously used by the SLC processors
  • ControlLogix L8X controllers
    • Solution for larger systems
    • Possible to combine several existing SLC processors into a single processor
    • Can put multiple processors in a single rack to economize on communications between them using the rack backplane – i.e. no load on the networking.
    • Supports several network options including legacy networks previously used by the SLC processors
    • Embedded Ethernet Ports for Communication (up to 1 GB)
    • USB port for alternative connection for programming
    • Includes Windows 10 Internet of Things Enterprise
      • Separate processor from Controller operations
      • Reduces the footprint for data and SCADA needs
      • Increases data exchange rates with other servers and systems
    • Expanded security
  • I/O Replacements
    • Chassis Based I/O
      • Upgrade entire system with I/O to match the new controller
      • Ensure your system is as up-to-date as possible following the migration
    • Remote I/O
      • Traditional Flex I/O 1794 Series
        • Large install base
        • Variety of I/O modules available
      • Flex 5000 I/O
        • Latest Flex Hardware
        • Up to 1 GB connection
        • Includes Safety I/O
      • Point I/O 1734 Series
        • Compact design
        • Low I/O count modules – Pay for what you need
      • SLC 1747-AENTR Ethernet Module
        • Fastest installation – replace the SLC500 processor with this module and use it as a remote rack to the new processor
        • Re-use the existing I/O
        • Allows phased migration to stretch costs over time
          • Can use removed I/O cards as spares for other systems until they can be migrated
          • Helps overcome the “It’s still working, why should I replace it?” obstacle
        • Not compatible with specialty modules or DeviceNet – Has some limitations

If you have any questions on SLC processors (or other legacy hardware) or facility modernization, please don’t hesitate to contact us.

eseincTech Corner: SLC Processors