ABB AC500 PM573 PLC Replacement Guide

Overview

The ABB AC500 PM573 CPU has served as a benchmark of reliable, high-performance processing within the global factory automation, process control, and infrastructure sectors. As a core component of the AC500 V2 PLC generation, the PM573 combines high-speed processing, flexible communication networks, and the robust S500 I/O expansion bus.

However, as industrial systems age, components face wear, and active product Lifecycles advance from "Classic" to "Obsolete," engineering teams must plan for replacement. Finding physical drop-in replacements, maintaining running system software, or migrating to modern hardware variants requires a clear hardware strategy.

This guide provides field engineers with the technical specifications, migration routes, compatibility matrices, and procedures required to successfully replace or upgrade an ABB AC500 PM573 central processing unit.

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Legacy Product Information

The PM573 CPU represents the standard tier of the AC500 V2 family. It is typically mounted on a TB500-series terminal base and is designed for applications requiring moderate processing power, localized I/O handling, and fieldbus connectivity.

Technical Specifications

• Part Numbers:
  • 1SAP130300R0171 (PM573 - without integrated RJ45 Ethernet)
  • 1SAP130300R0271 (PM573-ETH - with integrated RJ45 Ethernet)
• CPU Processor Type: 32-bit RISC processor.
• User Program Memory: 512 kB (RAM and Flash).
• User Data Memory: 512 kB (built-in SRAM, non-volatile).
• Cycle Execution Time: 0.05 µs per instruction (binary instructions).
• Onboard Interfaces:
  • 2 x serial interfaces (COM1 on Terminal Base as RS-232/RS-485, COM2 as RS-485).
  • 1 x Fieldbus Plug (FBP) connector.
  • 1 x RJ45 Ethernet port (specific to PM573-ETH variants; supports TCP/IP, Modbus TCP, HTTP, FTP).
• Expansion Limitations: Up to 10 local S500 expansion modules; up to 4 virtual/external communication couplers (installed on suitable TB5x1 terminal bases).
• Programming Environment: CoDeSys V2.3 mapped into ABB Automation Builder (formerly Control Builder Plus).

Current Lifecycle Status

The PM573 series has transitioned through the active sales lifecycle and is currently classified in the "Classic/Limited" support phase. Sourcing new components from standard distribution can carry long lead times or high pricing. As a result, critical process operators must identify viable refurbished, surplus, or direct-migration paths.

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Recommended Replacements

When upgrading or replacing a PM573, system integrators have three primary paths: direct-fit exact legacy hardware, current active V2 platform components, or a full migration to the modern AC500 V3 series.

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Compatibility Considerations

Before hot-swapping hardware or loading software files onto a different CPU module, engineers must carefully cross-reference physical, electrical, and logical protocols.

Physical Footprint and Terminal Bases

The PM573 sits atop a matching Terminal Base (TB511-ETH, TB521-ETH, or TB541-ETH).

• If you replace a PM573 with another V2 CPU (like PM583-ETH), it will snap into the exact same terminal base without requiring changes to underlying control cabling or the terminal block wiring.
• If you migrate to a V3 CPU (such as the PM5630-2ETH), the V3 unit remains physically compatible with legacy V2 terminal bases. However, you must verify that the bus expansion connectors match, as some modern modules utilize updated backplane buses.

Software and Runtime Differences

• V2 Runtimes (CoDeSys V2.3): The PM573 operates exclusively on the CoDeSys V2.3 runtime standard. It does not natively support V3 applications.
• V3 Runtimes (CoDeSys V3 / IEC 61131-3): Modern replacements like the PM5630 run on a updated execution engine. Programs must be opened in Automation Builder V2.x/V3.x, where the "Convert Project" wizard transforms standard V2 libraries to V3-compatible equivalents.

S500 Local I/O Bus

Both legacy PM573 systems and newer iterations support the local S500 I/O expansion system. Upgrading a CPU module does not require replacing down-line digital/analog cards (e.g., DX522 or AX522 modules). They remain addressable via the I/O bus protocol.

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Upgrade Benefits

Upgrading from a legacy PM573 to a newer processor variant (e.g., PM5630-2ETH) offers several operational advantages:

• Substantial Memory Headroom: Memory limitations on the legacy PM573 (512 kB) can hinder control algorithm additions. Stepping up to 8 MB allows for extensive diagnostics, recipes, and detailed event logging directly on the CPU.
• Enhanced Ethernet and Communication Protocols: Newer V3 CPUs support concurrent OPC UA (Server & Client), MQTT, and refined Modbus TCP architectures to facilitate secure IT/OT connectivity and Industry 4.0 data exchange.
• Security Integration: Advanced user access control, encrypted boot processes, and secure protocols safeguard the plant floor from cyber threats.
• Hardware Lifecycle Extension: Installing an active V3 component secures support terms and spares availability for the next 10 to 15 years, reducing operational risk.

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Common Migration Challenges

• Address Space Mismatch: Legacy applications may utilize specific memory addresses (%MW, %MD) that align differently on higher-tier CPUs. Always run an address integrity check during compilation.
• Library Incompatibilities: Certain older user library functions, specifically custom communication wrappers (e.g., SysLibCom or custom Modbus RTU drivers), will not directly interface with V3 runtimes. They must be remapped to clean system functions in the programming tool.
• Serial Port Baud Rates: RS-485 terminations on the newer CPUs may exhibit different internal biasing characteristics. Check termination resistors (typically 120 ohms) when moving serial lines over.

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Step-by-Step Replacement Procedure

Follow this technical procedure to swap an existing PM573 CPU with a direct replacement (PM573-ETH or PM583-ETH).

   [ POWER OFF SYSTEM ] ---> [ LABEL & DETACH CABLES ] ---> [ UNLATCH & REMOVE CPU ]
           |                                                        |
           v                                                        v
 [ CHECK BACKPLANE PINS ] <--- [ MOUNT INTEGRAL REPLACEMENT ] <--- [ CLEAN TERMINAL BASE ]
           |
           v
 [ PLUG ETH & SERIALS ]  ---> [ POWER UP & MEASURE ]  ---> [ UPLOAD RUNTIME PROGRAM ]

Phase 1: Preparation & Backup

1. Connect your engineering workstation to the running PM573.
2. Go to Automation Builder and perform an upload of the current project (if the source project is not archived on-site). Ensure you upload all custom libraries (.lib files).
3. Export the persistent and retain variable list values to prevent losing calibration metrics, runtime hours, or PID tuning setpoints.

Phase 2: Isolation & Mechanical Disassembly

1. Open the local isolation breaker to de-energize the PLC power supply (typically 24V DC). Warning: Verify that all internal and external field wiring is dead using a calibrated digital multimeter.
2. Clearly label and disconnect the RJ45 Ethernet cables, serial DB9 or terminal block connections, and any Fieldbus Plug connectors.
3. Locate the mechanical locks/slides on the top and bottom of the CPU module on the terminal base.
4. Release the locking tabs and gently pull the CPU straight out of the base module to prevent bending the backplane pins.

Phase 3: Inspect and Inspect

1. Examine the female connector sockets on the TB5xx terminal base. Blow out any dust or debris with clean, dry compressed air.
2. Inspect the male connection pins on the rear of the replacement CPU module for misalignment.

Phase 4: Installation and Integration

1. Align the replacement PM573 or PM583 CPU straight over the terminal base slot.
2. Firmly press the module in place until the mechanical locks click on both sides.
3. Re-insert the RJ45 and serial communication connections.

Phase 5: Commissioning & Startup

1. Apply 24V DC control power to the terminal base.
2. Observe the CPU's diagnostic display and status LEDs (PWR, RUN, ERR). Ensure the PWR LED lights solid green.
3. Establish a standard serial or Ethernet configuration bridge via Automation Builder.
4. Set the IP parameters and download the compiled system program, and write the retain/persistent variable values back into memory.
5. Place the CPU into RUN mode. Check for any errors on the local S500 expansion bus before running field equipment.

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Frequently Asked Questions

Can I replace a standard PM573 with a PM573-ETH?

Yes. The PM573-ETH includes an integrated RJ45 onboard interface. You will need to map the new IP config and Ethernet communication channels in Automation Builder, but the underlying application code structure and mounting profile remain identical.

How do I clear an "ERR" LED after sliding a replacement CPU in place?

The "ERR" LED indicates a hardware configuration mismatch or a missing platform boot project. Connect your computer to the CPU diagnostic port, read the log files in Automation Builder, and ensure you have compiled and downloaded the appropriate system target files.

Does the legacy PM573 support absolute address modification on the fly?

No. Standard modifications to mapped I/O coordinates require compiling and downloading a new boot project, which requires putting the CPU into "Stop" mode.

What is the maximum S500 local module expansion limit for the PM573?

The PM573 supports a maximum of 10 local S500 I/O expansion modules connected to the same terminal base assembly.

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Related Products & Families

To complete your system replacement, you may require additional parts from the ABB AC500 platform:

• Terminal Bases: TB511-ETH, TB521-ETH, and TB541-ETH modules.
• Digital I/O Expansion: DI524, DO524, and DX522 modules.
• Analog I/O Expansion: AI523, AO523, and AX522 modules.
• Fieldbus Couplers: CM572-DP (Profibus DP), CM579-PNET (Profinet), and CM588-CN (CANopen) modules.

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Need Help?

Replacing or upgrading older PLC controllers requires precise components and deep technical knowledge. If you want to avoid time-consuming software rebuilds by procuring high-quality, pre-tested legacy PM573 parts, we can help.

Palm Parts Solution supplies an extensive inventory of new, refurbished, and certified industrial surplus parts, including obsolete ABB AC500 components. Every part we sell is backed by our comprehensive warranty.

Contact our technical sales team down below to discuss your hardware replacement needs or search our catalog today.