Modernizing Legacy PLC Systems: How to Plan a Complete Controls Upgrade
Published by
Terry Meister
on
With RSLogix reaching end-of-life, industrial facilities must prepare now to avoid reactive maintenance, costly downtime, and part obsolescence. Legacy platforms like PLC-5 and SLC-500 series are increasingly difficult to support. When these systems fail, they rarely do so on your schedule.
Applied Manufacturing Technologies (AMT) helps manufacturers evaluate, plan, and execute control system migrations from outdated hardware and software to modern, supported platforms. Whether you're still using legacy processors or communication protocols like DH+ or DeviceNet, migrating successfully requires a structured, phased approach.
Migration projects can range from a single machine to a multi-line facility, but regardless of size, success depends on planning. Poor preparation often leads to unnecessary downtime, scope creep, or compatibility issues. At AMT, we take a methodical, phased approach to help clients minimize risk, ensure hardware and software compatibility, and stay within operational constraints.
The following steps outline how we evaluate legacy systems, design a path forward, and execute the migration with minimal disruption.
- Inventory and Documentation Review
Create a complete snapshot of your installed hardware, wiring, I/O lists, and programs. - Criticality and Risk Assessment
Evaluate what systems are most vital to operations and the consequences of failure. - Hardware Compatibility Analysis
Determine if existing panels, enclosures, and field devices can be reused or require upgrades. - Software Conversion Plan
Transition control logic from RSLogix to Studio 5000, including tag structure changes. - Network and Communication Upgrade
Replace legacy protocols with modern Ethernet/IP for better speed and visibility. - Downtime and Commissioning Strategy
Develop phased cutovers, weekend swaps, or shadow systems to avoid extended outages. - Budget and Resource Planning
Provide cost estimates and staff allocations to align with plant shutdown windows and goals.
Why Is RSLogix Going Away? Rockwell Automation is focusing support and development on Studio 5000 and Logix-based platforms. As a result, RSLogix 5 and 500—and their associated hardware (PLC-5, SLC-500)—are no longer supported. That means:
- No new firmware updates
- Parts are increasingly hard to source
- Security vulnerabilities may go unpatched
If your control system fails, you may not be able to recover without redesigning anyway.
Legacy vs. Modern Control Systems: A Quick Comparison
Each path includes unique challenges related to hardware compatibility, software conversion, and network configuration.
|
Category |
Legacy System |
Modern Replacement |
|
Processor |
PLC-5 |
ControlLogix |
|
SLC-500 |
CompactLogix or ControlLogix |
|
|
Programming Environment |
RSLogix 5 / 500 |
Studio 5000 (Logix Designer) |
|
Network Protocol |
DH+ (Data Highway Plus) |
Ethernet/IP |
|
DeviceNet |
Ethernet/IP |
|
|
I/O Communication |
Proprietary, slower communication speeds |
Ethernet-based, faster and scalable |
|
Parts Availability |
Limited or discontinued |
Fully supported and stocked |
|
Integration Capabilities |
Minimal connectivity to IIoT or higher-level systems |
Native support for Ethernet/IP and modern SCADA |
|
Migration Risk |
Unplanned downtime due to unsupported hardware |
Phased upgrades with planned cutovers |
Key components typically involved in migrating from RSLogix-era systems to modern architectures using ControlLogix, Studio 5000, and Ethernet/IP.
Avoid These Common Migration Mistakes
- Underestimating Downtime Needs: Assuming a swap can happen in a single weekend without prep.
- Skipping Network Evaluation: Legacy protocols like DH+ often require complete rewiring and reconfiguring.
- Lack of Documentation: Many legacy systems have outdated or missing documentation, making planning more difficult.
- No Phased Plan: Trying to convert everything at once instead of phasing in changes.
AMT addresses each of these during the planning phase, reducing surprises mid-project.
Don’t Wait for Failure to Force Your Hand
No facility benefits from running unsupported control systems. A planned migration avoids the operational, financial, and safety risks of an emergency breakdown. Even if your team isn’t ready to begin tomorrow, now is the time to build a realistic roadmap.
Start With a Site Assessment
Every successful migration starts with a clear understanding of what you have—and where the risks are. AMT can help you build a step-by-step plan that works within your downtime windows, budget, and technical needs.
To begin, schedule a system evaluation with our controls team.