Allen-Bradley 1747-L551/C – SLC 5/05 CPU with Ethernet | SLC 500 PLC Platform
Engineering Background: The Allen-Bradley SLC 500 series has been a cornerstone of North American industrial automation since the early 1990s. Designed by Rockwell Automation, the SLC 500 platform delivers deterministic ladder-logic execution in a compact, modular chassis—making it the preferred choice for discrete manufacturing, material handling, and process control applications where reliability and serviceability are paramount.
Product Positioning: The 1747-L551/C is the Series C revision of the SLC 5/05 processor—the highest-performance CPU in the SLC 500 family. It uniquely integrates a native 10/100 Ethernet/IP port alongside the standard DH-485 and RS-232 (DF1) channels, enabling direct SCADA, HMI, and MES connectivity without an additional communication module. This makes it the optimal upgrade path for legacy SLC 500 installations requiring modern network integration.
Complete Technical Specifications
| Parameter | Specification |
|---|---|
| Catalog Number | 1747-L551/C |
| Series / Revision | SLC 5/05, Series C |
| Manufacturer | Allen-Bradley / Rockwell Automation |
| Platform | SLC 500 |
| User Memory | 64K words (64,000 words) |
| I/O Addressing | Up to 4,096 I/O points |
| Communication Port 1 | Ethernet/IP – 10/100 Mbps, RJ-45 |
| Communication Port 2 | DH-485 (AIC+ compatible) |
| Communication Port 3 | RS-232 (DF1 Full/Half Duplex, DH-485, ASCII) |
| Scan Time | ~1 ms/K (typical ladder logic) |
| Battery Backup | Lithium battery (1747-BA), program retention on power loss |
| Operating Temperature | 0 °C to +60 °C (32 °F to 140 °F) |
| Storage Temperature | -40 °C to +85 °C |
| Relative Humidity | 5% to 95% non-condensing |
| Power Consumption | 800 mA @ 5 VDC (from chassis backplane) |
| Chassis Compatibility | All SLC 500 modular chassis (1746-A4 through 1746-A13) |
| Programming Software | RSLogix 500 / Studio 5000 Logix Designer (offline) |
| Certifications | UL, CE, CSA, C-Tick |
| Product Weight | Approx. 500 g |
| Country of Origin | United States |
Proven Application Environments
- Discrete Manufacturing: Automotive assembly lines, stamping presses, conveyor sequencing, and robotic cell coordination requiring deterministic scan times.
- Material Handling: Sortation systems, palletizers, and warehouse automation where Ethernet/IP connectivity to WMS/MES is required.
- Food & Beverage: Packaging lines, filling machines, and CIP (Clean-In-Place) systems operating in washdown-adjacent environments.
- Water & Wastewater: Pump station control, SCADA-integrated monitoring, and remote I/O expansion via 1747-ASB adapters.
- OEM Machine Builders: Retrofit and modernization projects replacing older SLC 5/01–5/04 processors with Ethernet-capable hardware while preserving existing I/O wiring and ladder programs.
- Pharmaceutical & Life Sciences: Validated process control environments where SLC 500 platform continuity is required for regulatory compliance (21 CFR Part 11 adjacent).
Engineering Advantages
- Native Ethernet/IP: Eliminates the need for a 1761-NET-ENI or 1747-AENTR bridge module—reducing panel footprint, wiring complexity, and single points of failure.
- 64K Word Memory: Maximum memory capacity in the SLC 500 family supports large ladder programs, extensive data tables, and complex recipe management.
- Triple-Port Communication: Simultaneous Ethernet/IP, DH-485, and RS-232 connectivity enables integration with legacy DH-485 networks while adding modern Ethernet infrastructure.
- Series C Reliability: Incorporates Rockwell Automation’s latest hardware revisions for improved EMI immunity and extended MTBF compared to Series A/B.
- Hot-Swap Compatible: Can be replaced in a powered chassis (with appropriate precautions) minimizing production downtime during maintenance.
- RSLogix 500 Ecosystem: Full compatibility with the mature RSLogix 500 toolchain including online editing, forced I/O, and trend monitoring.
System Architecture & Signal Flow
The 1747-L551/C occupies Slot 0 of any SLC 500 modular chassis. The CPU communicates with I/O modules via the SLC 500 backplane at 5 VDC. Program execution follows a deterministic scan cycle: Input Scan → Program Scan → Output Scan → Housekeeping. The integrated Ethernet/IP port supports both explicit messaging (for data exchange with SCADA/HMI) and implicit I/O messaging (for real-time I/O over EtherNet/IP). The DH-485 port supports multi-drop networks of up to 32 nodes at 19.2 Kbps, while the RS-232 port handles point-to-point DF1 communication with programming terminals or operator interfaces.
Typical Integration Topology:
- Ethernet/IP → Managed switch → FactoryTalk View SE / Ignition SCADA / MES
- DH-485 → AIC+ → Legacy PanelView 550/600/900 HMIs
- RS-232 → Programming laptop (RSLogix 500 via 1747-CP3 cable)
Sourcing & Quality Verification
- Source: Procured from authorized distributors and verified OEM surplus channels. Each unit undergoes incoming inspection before listing.
- Authenticity: All Allen-Bradley catalog numbers are cross-referenced against Rockwell Automation’s official product database. Counterfeit risk mitigation is a core procurement standard at Konmask.
- Condition: Units are listed as New, Refurbished, or Surplus-Tested. Condition is explicitly stated on each order confirmation.
- Warranty: 12-month functional warranty against manufacturing defects. DOA replacement within 30 days of receipt.
- Testing: CPU modules are bench-tested for power-on, communication port functionality, and memory integrity prior to shipment where applicable.
Procurement Process
- Inquiry: Submit your RFQ via the product page or email support@konmask.com with quantity, required delivery date, and destination country.
- Quotation: Receive a formal quotation within 1 business day including unit price, lead time, shipping options (DHL/FedEx/UPS), and export documentation availability.
- Order Confirmation: Purchase order or online checkout accepted. Proforma invoice issued for wire transfer payments.
- Export & Shipping: EXW Xiamen / CIF destination available. Commercial invoice, packing list, and certificate of origin provided. HS Code: 8537.10 (programmable controllers).
- After-Sales: Technical support available via email and WhatsApp. Replacement or refund processed per warranty terms.
Technical FAQ
Q: Is the 1747-L551/C compatible with ControlLogix or CompactLogix chassis?
A: No. The 1747-L551/C is exclusively compatible with SLC 500 modular chassis (1746-Axxx series). For ControlLogix or CompactLogix, different catalog numbers apply.
Q: Can I use RSLogix 5000 / Studio 5000 to program this CPU?
A: No. The SLC 5/05 requires RSLogix 500 (v8.0 or later recommended). Studio 5000 is for Logix5000-family controllers only.
Q: What cable is required for RS-232 programming?
A: Use the 1747-CP3 (9-pin D-sub to RJ-45) cable. A USB-to-serial adapter may be required on modern laptops.
Q: Does the Ethernet port support DHCP?
A: Yes. The 1747-L551/C supports both static IP and DHCP address assignment, configurable via RSLinx Classic or BOOTP/DHCP Server utility.
Q: What is the battery part number for memory backup?
A: The replacement battery is 1747-BA (3V lithium). Battery life is typically 3–5 years under normal operating conditions.
Q: Can this module replace a 1747-L551/A or /B without program changes?
A: Yes. Series revisions (A/B/C) are functionally compatible. The program can be uploaded from the existing CPU and downloaded to the /C revision without modification.
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