CJ1W-SRM21 CJ Series CompoBus/S Master Unit | Omron

The Original New Omron CJ1W-SRM21 is a CompoBus/S Master Unit for the SYSMAC CJ series programmable logic controller (PLC) platform, designed to reduce wiring between sensors, actuators, and the PLC by serving as the communication master for a high-speed remote I/O system. As a CJ-series Special I/O Unit, it supports up to 256 I/O points and 32 slave devices per master unit. Providing two selectable communications modes—High‑speed Communication Mode (750 kbps) and Long‑distance Communication Mode (93.75 kbps)—it offers flexibility for distributed I/O control in machine automation, packaging machinery, and material handling systems. The unit mounts on a DIN rail via a spring terminal and supports CE, cULus, NK, and Lloyd‘s certifications.

⚠️ Important Product Status Note:

This product has been discontinued by Omron. The end-of-order date was August 2022. The recommended replacement is the CJ1W-CRM21. This product remains available for maintaining existing installations while supplies last. For new designs, please consider the recommended replacement model.

Core Engineering Highlights:
256 (128 inputs / 128 outputs) or 128 (64 inputs / 64 outputs) I/O points (switch‑selectable) | 32 slaves per master | Communications cycle time: 0.5 ms at 750 kbps | Communications distance: up to 500 m at 93.75 kbps | Two communication modes: High‑speed (750 kbps) and Long‑distance (93.75 kbps) | Supports 2‑conductor VCTF, 4‑conductor VCTF, and Special Flat Cable | Manchester coding with error control (Manchester code check, frame length check, parity check) | 20 words allocated for 256 I/O (8 input, 8 output, 4 status) / 10 words for 128 I/O (4 input, 4 output, 2 status) | Weight: 0.09 kg (0.19 lbs) | IP20 protection | 0°C to +55°C operating temperature

Key Features:

• Original New Omron CJ1W-SRM21 module

• CompoBus/S Master Unit for high-speed ON/OFF remote I/O bus

• Supports up to 256 I/O points (128 inputs and 128 outputs) or 128 I/O points (64 inputs and 64 outputs) via switch selection

• Supports up to 32 slave devices per master unit

• Two communication modes: High‑speed Communication Mode (750 kbps) and Long‑distance Communication Mode (93.75 kbps)

• Communications cycle time as fast as 0.5 ms

• Communications distance up to 500 m in long‑distance mode

• Free wiring with any branching method up to 200 m in long‑distance mode

• Supports up to 40 Master Units per CPU

• Node address: 8 addresses per node

• Status information: Communications Error Flags and Participation Flags

• DIN rail mounting with spring terminal

Applications:

• Connecting remote I/O slaves (sensors, actuators, limit switches, pilot lamps) in machine automation

• Factory automation systems requiring distributed I/O points

• Packaging machinery and material handling systems

• Assembly lines and conveyor control with remote I/O modules

• High-speed remote I/O bus systems for sensors and actuators

Technical Specifications:

Communications Distance:

System Compatibility:

• Compatible with Omron SYSMAC CJ1, CJ2, and CS1 series CPU units

• Not compatible with Machine Automation Controller NJ‑series CPU units

• Uses CJ-series I/O bus and mounts on CPU rack or expansion rack

• When using as a replacement for the discontinued CQM1-SRM21-V1, the entire I/O system must be replaced with CJ‑series hardware

• I/O power supply voltage: 24 V DC (from connected slaves, not supplied by master unit)

• Compatible with CompoBus/S remote I/O slave units: SRT2 series, SRT1 series, DRT2 series

• Programming software: CX-Programmer (CX-One) / Sysmac Studio

Related Products:

• CJ1W-CRM21 – CompoBus/S Master Unit (recommended replacement)

• CS1W-CRM21 – Recommended substitute (alternative for CJ1W-SRM21)

• CJ1W-SRM21 – Current model (obsolete, no longer manufactured)

• CJ1W-PA205R – Power supply unit for CJ series CPU rack

• SRT1 Series / SRT2 Series – CompoBus/S remote I/O slave units

• CJ1W-DRM21 – DeviceNet Master Unit for CJ series

PLC ERA is an independent industrial automation distributor supplying genuine Original New products through established global supply channels. All products are factory sealed when applicable and undergo quality inspection prior to shipment. Omron and SYSMAC are trademarks of Omron Corporation.