Allen-Bradley 1747-L542 SLC 5/04 Processor 32KB

1747-L542 | Allen-Bradley SLC 500 CPU Module

Product Introduction

The 1747-L542 processor belongs to the trusted SLC 500 family from Allen‑Bradley. This SLC 5/04 unit offers a balanced mix of memory capacity and I/O handling for medium‑scale automation tasks. It mounts directly into slot 0 of any standard SLC chassis, such as the 1746‑A2 or 1746‑A13.

Additionally, this controller features two integrated communication ports: one RS‑232 port and one Data Highway Plus (DH+) port. These interfaces enable seamless connectivity with operator panels, supervisory systems, and even other Rockwell controllers like PLC‑5 or CompactLogix.

For operational peace of mind, the 1747-L542 includes diagnostic LEDs for run status, CPU faults, forced I/O, and battery condition. A physical keyswitch lets you change the operating mode quickly and securely. Whether you are upgrading an existing line or building a new control panel, this processor provides a dependable foundation.

Technical Specifications

The 1747-L542 SLC 5/04 processor comes with 32 KB of battery‑backed RAM, which stores up to 32,000 user program words. Within this memory, 4K words are reserved for data tables, while 28K words hold your application logic.

In terms of I/O capacity, this controller supports a maximum of 4,096 discrete inputs and 4,096 discrete outputs. It also handles up to 480 analog I/O points locally. The system accommodates 3 local I/O chassis with a total of 30 slots, giving you ample room for expansion modules.

Performance is another strong point. The typical program scan time is 0.9 ms per Kword, while the I/O scan completes in just 0.225 ms. Bit execution runs at 0.37 µs, ensuring responsive control for most industrial processes. Furthermore, the backplane draws 1 A at 5V DC and 175 mA at 24V DC from the system power supply.

Communication and Diagnostics

Onboard communication includes a RS‑232 port for point‑to‑point connections and a DH+ port for high‑speed peer‑to‑peer networking. This DH+ capability allows the 1747-L542 to participate in multi‑processor systems or pass‑through messaging with other Allen‑Bradley platforms.

For maintenance and troubleshooting, the front panel provides clear status indicators. These LEDs show Run, CPU Fault, Forced I/O, Battery Low, RS‑232 activity, and DH+ activity. The battery‑backed design uses a standard 1747‑BA battery, while an optional 1747‑M13 Flash EPROM module offers additional program backup.

Mechanical and Environmental Ratings

The 1747-L542 operates reliably in a temperature range of 0 °C to 60 °C (32 °F to 140 °F). For storage, it withstands temperatures from ‑40 °C to 85 °C (‑40 °F to 185 °F). The ambient relative humidity must stay between 5% and 95%, non‑condensing.

Mechanically, this processor endures a vibration of 2.5G at 57 to 2000 Hz and a displacement of 0.015 inches peak‑to‑peak at 5 to 57 Hz. It also resists operating shocks up to 30G. These robust specifications make the 1747-L542 suitable for demanding factory floor environments.

Installation Guidelines

Installing the 1747-L542 is straightforward. First, ensure the chassis power supply is turned off. Insert the processor into slot 0 of your SLC chassis, applying even pressure until it seats firmly in the backplane connector. Secure the module with the retaining screws if provided.

Next, connect your DH+ network or RS‑232 cable to the corresponding ports as needed. Finally, apply power and observe the status LEDs. A steady green Run LED indicates normal operation. Always handle the unit with proper ESD precautions to avoid damaging sensitive components.

Packaging List

Your shipment for the 1747-L542 includes the following items:

• One Allen‑Bradley 1747-L542 SLC 5/04 processor module

• One keyswitch (installed)

• Product documentation and installation instructions (digital download)

Note: The battery (1747‑BA) and memory backup module (1747‑M13) are optional accessories and may be ordered separately.

Shipping Information

We ship all orders via FedEx, UPS, or DHL to ensure fast and reliable delivery. Tracking numbers are provided upon dispatch. Please contact our sales team for shipping rates and estimated delivery times to your region.

Frequently Asked Questions (FAQ)

1. What is the difference between the 1747-L542 and the 1747-L541?
The 1747-L542 offers 32 KB of user memory, which is double the capacity of the 1747-L541 (16 KB). Both are SLC 5/04 processors, but the L542 suits larger programs and more complex logic.

2. Can this processor communicate with a ControlLogix system?
Yes. The 1747-L542 supports DH+ messaging and can exchange data with ControlLogix, CompactLogix, and PLC‑5 platforms via pass‑through or gateway devices.

3. Is the memory battery included with the 1747-L542?
No. The battery (catalog number 1747‑BA) is sold separately. It provides backup for the RAM when the system power is off.

4. How do I clear a CPU fault on this processor?
First, identify the fault using the status LED or programming software. Then, cycle the keyswitch from PROG to RUN or use RSLogix 500 to clear the fault. If the issue persists, check your program logic and I/O connections.

5. What happens if the battery voltage gets low?
The front‑panel Battery Low LED will illuminate. You should replace the battery soon to prevent losing your program. The processor retains its program during a battery swap if the power is on.