Allen-Bradley 1747-L551 SLC 500 PLC CPU Module is a SLC 5/05 processor for the Allen-Bradley SLC 500 family, designed to control mid‑size automation tasks within a 1747 modular chassis. It provides 16,000 words of user memory, supports up to 3 local I/O chassis and 30 I/O slots, and handles up to 4,096 discrete inputs and 4,096 discrete outputs with up to 480 analog I/O points. It includes Ethernet and RS‑232 communications (DH‑485, DF1, or ASCII) and uses Flash EPROM for backup memory, with a program scan time of about 0.9 ms. This CPU is discontinued by Rockwell Automation as of December 31, 2021, though remains available from some third‑party distributors.
