Allen-Bradley 1747-L542 PLC Module

Allen-Bradley 1747-L542 is a SLC 500 Series CPU module (5/04) that functions as the central processor for legacy SLC 500 PLC systems, occupying a 1747-compatible rack in Rockwell Automation’s modular control architecture. It provides 32K words of user memory, with 28K reserved for program storage and 4K for data, enabling sizable ladder logic programs and data handling for industrial automation tasks. The unit includes an RS-232 serial port for programming and diagnostic access and a DH+ communications port for networked I/O, supporting integration with existing Allen-Bradley networks. When paired with compatible I/O modules and a 1747 chassis, the 1747-L542 can support large configurations—up to 4,096 discrete I/O points and up to 480 analog I/O points, depending on the I/O modules used and system design. This processor is typically programmed with RSLogix 500 and is commonly employed in manufacturing environments for machine control, sequential operations, and simple analog/digital interfacing, making it a robust choice for legacy automation projects or rebuilds where SLC 500 hardware remains in service. Variants such as 1747-L542-CC offer conformal coating for harsher environments while preserving the same core CPU capabilities.