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Part of the Omron CJ-Series PLCs series — see the full model table, lifecycle status and replacement parts.

Omron CJ1W-SRM21 — front view of the CJ1 CompoBus/S Master showing the Omron model label, the 17.5 mm slim-line housing, the two rotary switches for node address and baud rate, and the four CompoBus/S status LEDs

Omron CJ1W-SRM21 — CJ1 CompoBus/S Master Unit

SKU: CJ1W-SRM21

USD 80.00

CJ-series CompoBus/S master unit, 256 I/O max, 32 slaves, 750 kbps. Discontinued 2022, spare only.

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Product Overview

The Omron CJ1W-SRM21 is a CJ-series CompoBus/S master unit for high-speed remote I/O It is manufactured by Omron Corporation. Hengyixin Automation stocks this controller in Xiamen and ships within 3-5 business days to most Asian, European, and North American ports. Specifications on this page were checked against Omron's CJ-series Serial Communications Unit documentation.

The unit sits on the CJ I/O bus and exchanges remote I/O with up to 32 CompoBus/S slaves. Total I/O is 256 points (128 in / 128 out) or 128 in the smaller mode.

For a PROFIBUS-DP master on the same CJ1 form factor, pick the CJ1W-PRM21; for DeviceNet, pick the CJ1W-DRM21. Key specs: Unit Type CJ1 Special I/O Unit (DIN-rail mount); I/O Points 256 max (128 in / 128 out) or 128 (64 / 64), switch-selectable; Slaves Up to 32 slaves per master; Baud Rate 750 kbps high-speed mode; 93.75 kbps long-distance mode; Cycle Time 0.5 ms at 750 kbps with 8 in + 8 out slaves; Main Line Length 100 m at 750 kbps on 2-conductor VCTF; 500 m at 93.75 kbps; Allocated Words 20 CIO words for 256 I/O; 10 CIO words for 128 I/O; Current Consumption 5 VDC, 0.15 A from CJ backplane.

Key Features

  • CJ1 Special I/O Unit that masters a CompoBus/S remote I/O network
  • 256 I/O max across 32 slaves (or 128 I/O in low mode)
  • High-speed mode 750 kbps with 0.5 ms cycle, or long-distance mode 93.75 kbps up to 500 m
  • 5 V 0.15 A from CJ backplane, 17.5 mm wide, DIN-rail mount; discontinued Aug 2022
  • SKU: CJ1W-SRM21
  • Series: Omron CJ-series CompoBus/S Master Unit
  • I/O: 256 I/O

Best-Fit Applications

  • Spare master drop-in for an existing CompoBus/S remote I/O network where the previous CJ1W-SRM21 failed and the field wiring is CompoBus/S
  • Replacement master for a CS1W-SRM21 cell that needs to be ported onto a CJ1M-CPU21 rack on a similar CompoBus/S network
  • Service stock for an automotive weld line where the cabinet is still wired for CompoBus/S and a CJ1W-SRM21 is needed to keep it running

Buying Checklist

  • Pick the CJ1W-SRM21 when you have an existing CompoBus/S network and need a spare master that fits the CJ1 rack.
  • Pick the CJ1W-CRM21 instead for a current-production CompoNet master with the same CJ1 form factor.
  • Pick the C200HW-SRM21-V1 instead when the host is a CS1 or C200H rack and the master needs to clip on the CPU bus.

Technical Specifications

Manufacturer Omron Corporation (Japan)
Series Omron CJ-series CompoBus/S Master Unit
Model / SKU CJ1W-SRM21
Unit Type CJ1 Special I/O Unit (DIN-rail mount)
I/O Points 256 max (128 in / 128 out) or 128 (64 / 64), switch-selectable
Slaves Up to 32 slaves per master
Baud Rate 750 kbps high-speed mode; 93.75 kbps long-distance mode
Cycle Time 0.5 ms at 750 kbps with 8 in + 8 out slaves
Main Line Length 100 m at 750 kbps on 2-conductor VCTF; 500 m at 93.75 kbps
Allocated Words 20 CIO words for 256 I/O; 10 CIO words for 128 I/O
Current Consumption 5 VDC, 0.15 A from CJ backplane
Status Discontinued August 2022; supported as spare, replace with CompoNet

FAQ for CJ1W-SRM21

Is the CJ1W-SRM21 still in production?
No. Omron discontinued the CJ1W-SRM21 in August 2022. It is still sold as a spare part for existing CompoBus/S networks, but new machines should use a CJ1W-CRM21 CompoNet master with SRT2-series slaves.
How many slaves can the CJ1W-SRM21 address?
Up to 32 slaves per master, with up to 256 I/O points (128 in / 128 out) in high-I/O mode or 128 I/O points in the smaller mode. Mode is set on the rotary switch on the face of the unit.
Can the CJ1W-SRM21 work on an NJ-series controller?
No. The CJ1W-SRM21 is for CJ-series PLCs only. The Omron Machine Automation Controller NJ-series does not support CompoBus/S masters; use a CompoNet or EtherCAT master on those CPUs.

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