ControlLogix Controllers vs Guardlogix Controllers
Allen-Bradley’s Logix 5000 controller platform includes a wide array of controller families, such as ControlLogix, GuardLogix, Armor ControlLogix, Armor GuardLogix, CompactLogix, and Compact GuardLogix. Among them, ControlLogix and GuardLogix are widely used in large-scale industrial automation systems. While both are based on the same core architecture, GuardLogix includes enhanced features for functional safety.
Key Differences Between ControlLogix and GuardLogix Controllers
1. Safety Capabilities
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ControlLogix: Standard controller with no integrated safety functions.
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GuardLogix: Combines a standard controller with a safety controller in a single unit. Includes a self-configuring safety partner for SIL 3 and PLe/Cat. 4 applications.
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Safety Memory Lock: Once configured, safety memory is locked and immutable. However, standard functions remain editable online.
2. Safety Partner Integration
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GuardLogix: The safety partner is configured automatically and runs independently to ensure safety integrity. One download configures both standard and safety applications.
3. Task Management
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ControlLogix: Supports 32 standard tasks with one continuous task and 15 priority levels.
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GuardLogix: 31 standard tasks and 1 safety task. The safety task runs periodically and is user-prioritized with watchdog timers.
4. Memory Allocation
| Controller Model | User Memory | Safety Memory (GuardLogix Only) |
|---|---|---|
| 1756-L81E | 3 MB | N/A |
| 1756-L81ES | 3 MB | 1.5 MB |
| 1756-L72 | 4 MB | N/A |
| 1756-L72S | 4 MB | 2 MB |
5. Redundancy
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ControlLogix: Supports controller redundancy using two synchronized chassis.
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GuardLogix: No controller redundancy. The safety partner ensures functional safety redundancy only.
6. Safety Communication
Only GuardLogix supports:
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EtherNet/IP (CIP Safety peer-to-peer)
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DeviceNet Safety
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ControlNet Safety
7. Supported Safety Languages
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GuardLogix supports ladder logic for safety programming.
Similarities Between ControlLogix and GuardLogix
1. Built-in Communication Ports
| Controller Family | USB | Serial | Integrated Ethernet |
| 5580 | Yes | No | Yes |
| 5570 | Yes | No | Optional via module |
| 5560 | No | Yes | Optional via module |
2. Supported Communication Protocols
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EtherNet/IP
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ControlNet
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DeviceNet
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DH+
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Remote I/O
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SynchLink
3. Additional Memory Types
| Controller Model | I/O Memory | Non-Volatile Memory (SD) |
| 1756-L7x | 0.98 MB | 1–2 GB |
| 1756-L6x | 478 KB | 128 MB |
| 1756-L8x | Dynamic | 2 GB |
4. Network and Controller Connections
| Model | Max Ethernet/IP Nodes | Max Controller Connections |
| L82E | 80–165 (version-based) | 500 |
| L82ES | 165 | 500 |
| L6x / L6xS | N/A | 250 |
| L7x / L7xS | N/A | 500 |
5. Energy Storage
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L8x series: Built-in, non-removable energy module
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L7x series: Supports both removable and non-removable
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L6x series: Uses lithium battery (optional use)
6. Electrical Specifications
| Series | Voltage Inputs | Power Dissipation | Heat Generation |
| 5580 | 1.2V @ 5 mA, 5.1V @ 1.2A | 6.2 W | 21.2 BTU/hr |
| 5570 | 1.2V @ 5 mA, 5.1V @ 800 mA | 2.5 W | 8.5 BTU/hr |
| 5560 | 5.1V @ 1.2A, 24V @ 14 mA | 3.5 W | 11.9 BTU/hr |
7. Programming Languages Supported
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Ladder Logic Diagram (LD)
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Function Block Diagram (FBD)
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Sequential Function Chart (SFC)
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Structured Text (ST)
8. I/O and Motion Control Support
| Series | Max Digital I/O | Analog I/O | Total I/O | Motion Axes |
| 5580 | 128,000 | 4,000 | 128,000 | 256 |
| 5570/5560 | 128,000 | 4,000 | 128,000 | 128 |
Conclusion ControlLogix controllers are highly reliable for complex automation tasks, with flexibility in redundancy and high-speed processing. GuardLogix controllers add a critical safety layer for applications demanding functional safety and compliance with international standards (SIL 3, PLe). The choice between them should be based on the specific safety requirements of your system.
Need Help Choosing the Right Controller?
Contact our automation experts today:
PLG Automation
Email: sales@plgautomation.com
Phone: 800-906-9271