Omron CJ1W-SRM21 CJ Series CompoBus/S Master Unit

Omron CJ1W-SRM21 is a CompoBus/S Master Unit for CJ-series PLC systems. CompoBus/S is a high-speed I/O bus that reduces wiring between sensors, actuators, and the PLC. Used as a remote I/O communications master for CJ-series Special I/O Units. Supports up to 256 I/O points and 32 slave devices per master unit. Provides two selectable communications modes: High‑speed Communication Mode (750 kbps) and Long‑distance Communication Mode (93.75 kbps). 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

Core Specifications:

• Product type: CJ‑series Special I/O Unit (CompoBus/S Master Unit)

• Communications protocol: CompoBus/S dedicated protocol, Manchester coding

• Transmission speed: High‑speed mode 750 kbps / Long‑distance mode 93.75 kbps

• I/O points per master: Switch‑selectable 256 (128 inputs, 128 outputs) or 128 (64 inputs, 64 outputs)

• Allocated words (for 256 I/O): 20 words (8 input, 8 output, 4 status)

• Allocated words (for 128 I/O): 10 words (4 input, 4 output, 2 status)

• Connectable slaves: 32 devices per master

• Mountable master units per CPU: up to 40

• Node address: 8 addresses per node

• Status information: Communications Error Flags, Participation Flags

• Current consumption (5 V DC): 0.15 A

• Current consumption (24 V DC): not applicable

• Unit numbers allocated: 1 or 2 (variable)

• Connection type: Spring terminal (screwless communications connector)

• Protection rating: IP20

• Dimensions (W × H × D): 31 mm × 90 mm × 85 mm (approx.)

• Weight: approx. 200 g

• Operating temperature: 0 °C … 55 °C

Communications Specifications:

• Cable types: 2‑conductor VCTF cable (0.75 mm² × 2), 4‑conductor VCTF cable (0.75 mm² × 4), special flat cable

• High‑speed mode (750 kbps) with 2‑conductor VCTF cable: main line length ≤ 100 m, branch line ≤ 3 m, total branch line ≤ 50 m

• Long‑distance mode (93.75 kbps) with 2‑conductor VCTF cable: main line length ≤ 500 m, branch line ≤ 6 m, total branch line ≤ 120 m

• High‑speed mode with special flat cable or 4‑conductor VCTF cable: main line length ≤ 30 m, branch line ≤ 3 m, total branch line ≤ 30 m

• Long‑distance mode with special flat cable or 4‑conductor VCTF cable: flexible branching, total cable length ≤ 200 m

• When fewer than 16 slaves are connected in High‑speed mode: main line length ≤ 100 m, total branch line ≤ 50 m

• Communications cycle time (High‑speed mode): 0.5 ms (8 inputs + 8 outputs slaves), 0.8 ms (16 inputs + 16 outputs slaves)

• Communications cycle time (Long‑distance mode): 4.0 ms (8 inputs + 8 outputs slaves), 6.0 ms (16 inputs + 16 outputs slaves)

Compatibility information:

• This communications module belongs to the Omron SYSMAC CJ series.

• Installs on CPU Rack or Expansion Rack via CJ I/O Bus.

• Compatible with CJ1, CJ2 and CS1 series CPU units.

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

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

• When using the CJ1W-SRM21 as a replacement for the discontinued CQM1-SRM21-V1, the entire I/O system must be replaced with CJ‑series hardware.

Standards & Compliance:
Refer to manufacturer official documentation for certification and compliance details (CE, cULus, NK, Lloyd, UC1 for hazardous locations approval).

Related Products:

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

• CJ1W‑SRM21 – current model (obsolete, no longer manufactured)

• CompoBus/S remote I/O slave units – SRT2 series, SRT1 series, DRT2 series

• CJ1W‑PA205R – power supply unit for CJ series CPU rack