Purchase now: Allen Bradley 1747-L542 SLC 5/04 Processor
Purchase now: Atlantechdrives provides you the 1747-L542, a powerful and highly resilient CPU processor belonging to the industry-standard Allen Bradley SLC 5/04 family. Designed to handle complex, mid-to-large scale industrial automation tasks, this processor features 32,000 words (32K) of user memory. This significantly expanded capacity allows automation engineers to program extensive ladder logic routines, configure multiple closed-loop PID controllers, and manage large data tables for recipe handling and shift tracking. The hallmark of the SLC 5/04 series is its built-in Data Highway Plus (DH+) communication port, which provides robust, token-passing network connectivity across long distances, making the 1747-L542 an essential component for synchronized manufacturing lines, SCADA data acquisition, and heavy material handling systems.
Technical Specifications of the 1747-L542
The 1747-L542 processor occupies slot 0 of any 1746 expansion chassis and relies on the backplane for its 5V DC power. It supports online programming edits, floating-point math, and advanced string manipulation instructions.
- Part Number: 1747-L542
- Processor Class: SLC 5/04 CPU
- Total User Memory: 32K Words (Instructions and Data)
- Channel 1 Port: DH+ (Data Highway Plus) via 3-pin Phoenix connector
- Channel 0 Port: RS-232 (Supports DF1, ASCII, DH-485 via adapter)
- Maximum Local I/O Capacity: 4096 inputs / 4096 outputs
- Maximum Local Chassis: 3 (Up to 30 slots total)
- Backplane Current Draw: 1.0 Amps at 5V DC
Expert Installation Advice: DH+ Baud Rates and Termination
Integrating the 1747-L542 into a legacy DH+ network requires careful physical configuration. Expert Tip: The Data Highway Plus network supports three different communication speeds: 57.6 kbps, 115.2 kbps, and 230.4 kbps. You cannot mix these baud rates on the same network wire. Before connecting the «Blue Hose» to the 3-pin Phoenix connector on the front of the processor, ensure your RSLogix 500 project is configured with the exact baud rate matching the rest of the network. Furthermore, physical termination is absolutely critical. If this processor is located at the physical end of the DH+ daisy-chain, you must install a terminating resistor (150-ohm for 57.6k/115.2k, or 82-ohm for 230.4k) across the Line 1 and Line 2 terminals to prevent signal reflection and network collision faults.
Maintenance and Diagnostics
The front panel of the 1747-L542 is equipped with several LED status indicators (RUN, FLT, BATT, FORCE, DH+, RS232) that serve as your first line of defense during a machine breakdown. If the red «FLT» (Fault) LED is flashing, the processor has encountered a major software error, such as a math overflow (dividing by zero) or an I/O rack communication loss. You must connect your laptop via the RS-232 port using a 1747-CP3 null modem cable to read the specific fault code in RSLogix 500, clear the fault, and switch the processor back to RUN mode.
Frequently Asked Questions (FAQs)
Q: Can I upgrade a 16K SLC 5/04 (1747-L541) directly to this 32K model?
A: Yes, the 1747-L542 is a direct drop-in replacement. You simply download your existing 16K program into the new processor, giving you 16K of free memory overhead for future machine upgrades and code expansion.
Q: Does the 1747-L542 support Ethernet communication?
A: Not natively. To connect this processor to an Ethernet/IP network, you must either use an external gateway (like the 1761-NET-ENI connected to the serial port) or upgrade the processor entirely to an SLC 5/05.
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This 32KB SLC 5/04 CPU features high-speed DH+ communication for enterprise-level networking with 1746-P2 power backup.
