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3. Key Technical Specifications
| Parameter | Value |
|---|---|
| Processor Type | SLC 5/01 |
| User Memory | 4K instructions |
| Max Discrete I/O | 960 (local) |
| Max Local Analog I/O | 480 |
| Max Chassis / Slots | 3 chassis / 30 slots total |
| Program Scan Time | 8 ms/K typical |
| I/O Scan Time | 2.6 ms typical |
| Communication Port | DH-485 (slave only – cannot initiate messages) |
| Memory Backup | Capacitor-backed RAM; optional EEPROM (1747-M1 / 1747-M2) |
| Backplane Current @ 5 V DC | 350 mA |
| Backplane Current @ 24 V DC | 105 mA |
| Installation Slot | Slot 0 only |
| Operating Temperature | 0 °C to +60 °C |
| Storage Temperature | –40 °C to +85 °C |
4. Product Introduction
The Allen-Bradley 1747-L514 is the 4K-memory version of the SLC 5/01 processor. It installs exclusively in Slot 0 of any 1746 modular chassis and supports up to three chassis with a total of 30 I/O modules.
It provides basic ladder logic execution, DH-485 slave communication for programming and data exchange, and capacitor-backed RAM with optional EEPROM modules for program retention. Typical scan times are 8 ms per K of program and 2.6 ms for I/O. This processor is suited for smaller, local-I/O applications where remote I/O scanning is not required.
5. Troubleshooting Quick Reference
| Symptom | Possible Cause | Relevance to this Part | Quick Check Method | Recommendation |
|---|---|---|---|---|
| No RUN LED, chassis powered | Processor not seated or backplane power low | ✅ High | Reseat module in Slot 0; measure 5 V and 24 V backplane | Confirm power supply capacity and seating |
| CPU FAULT LED on | Memory error, program corruption, or hardware fault | ✅ High | Clear faults in RSLogix 500; check battery/capacitor status | Reload program; replace if fault persists |
| Cannot establish DH-485 comms | Wrong node address, baud rate, or cabling | ✅ High | Verify node = 1, 19.2K baud default; check 1747-PIC or AIC | Match software settings; inspect cable and terminators |
| Program lost after power cycle | Capacitor discharged or battery dead | ✅ High | Check BATTERY LOW LED; install/replace 1747-BA or EEPROM | Install battery or EEPROM module for retention |
| I/O modules not recognized | Chassis expansion limit exceeded or addressing error | ❌ Medium | Confirm ≤ 3 chassis / 30 slots; verify I/O configuration | Reduce module count or correct addressing |
| Slow or erratic scan | Program size near 4K limit or heavy math | ❌ Low | Monitor scan time in software | Optimize logic or upgrade to higher-memory processor |
If the fault remains unresolved, capture LED status, fault codes, and program size details before contacting support.
1747-L514
1747-L514
6. Frequently Asked Questions (FAQ)
Q: Is the 1747-L514 still available new from Rockwell? No. The SLC 500 platform is discontinued. Units available today are New Surplus or refurbished. Confirm current stock and condition before ordering.
Q: What is the difference between the 1747-L511 and 1747-L514? The L511 has 1K user memory; the L514 has 4K user memory. All other core specifications (I/O limits, communication, scan times) are identical.
Q: Can the 1747-L514 initiate messages on DH-485? No. The SLC 5/01 DH-485 port operates in slave mode only. It responds to messages but cannot initiate them. Use an SLC 5/02 or higher if master messaging is required.
Q: Does the processor require a battery? The L514 uses capacitor-backed RAM that retains memory for a limited time after power loss. For long-term retention, install the optional 1747-BA lithium battery or an EEPROM module (1747-M1 or 1747-M2).
Q: Can this processor control remote I/O? No. The SLC 5/01 supports only local I/O in the chassis. Remote I/O scanning requires an SLC 5/02 or later processor plus a scanner module.
Q: Where must the 1747- be installed? It must be installed in Slot 0 of the primary 1746 chassis. It will not operate in any other slot.
Q: Why is New Surplus priced lower than original list? These are genuine Allen-Bradley processors from excess inventory or cancelled projects. They are unused and typically supplied with anti-static protection. They are not refurbished unless specifically stated.
