CPU capacity and expandability
The CJ1H-CPU66H is a high-end CPU in Omron's CJ1 series, offering 120K program steps and 256K memory — enough for mid-to-large machine control with complex logic and data handling. It expands to 40 modules across 3 racks, so it can handle a substantial I/O count and specialty modules like motion or serial communication. Built-in RS-232C port handles programming and simple serial device communication. For Ethernet or fieldbus, you'll need an add-on module in one of the expansion slots. Rated for 0°C to 55°C operating temperature, so it's fine in a ventilated cabinet but watch ambient if the panel runs hot.
How it compares to the CJ1H-CPU65H
The CJ1H-CPU65H is the closest sibling — same series, same expandability (40 modules, 3 racks), same RS-232C port, same weight and dimensions. The difference is program memory: the CPU66H has 120K steps and 256K memory, while the CPU65H has 60K steps and 128K memory. If your application fits within the smaller memory, the CPU65H is a drop-in replacement mechanically and electrically. If you need the extra capacity, the CPU66H is the only CJ1H option.
Integration notes
Mounts on DIN rail. Battery backup is built in for retaining program and data during power loss — replace the battery per Omron's schedule to avoid losing the program. CX-One software is used for programming and configuration. No display on the unit; all status is via LEDs and the software.