The Omron CJ1W-SRM21, also cataloged as the CJ1W-SRM21 Input Output Control Module, operates as a dedicated hardware component for CompoBus/S master communication execution and field I/O bus integration within Omron CJ-Series PLCs.

Technical Identifier Matrix

• Base Hardware Model: CJ1W-SRM21
• Full Part Number: CJ1W-SRM21
• Unit Classification: Special I/O Unit
• Compatible Controllers: Omron CJ-Series PLCs
• Max Mountable Master Units: 40 units per CPU system
• Node Addressing Capacity: 8 addresses per mode
• Maximum Slave Capacity: 32 connectable slaves

Hardware Specifications

Omron Backplane Bus Velocity & Field I/O Density Scaling

The CJ1W-SRM21 Special I/O Unit mounts directly onto the high-velocity SYSMAC CJ1 backplane bus, transferring cyclic CompoBus/S frame data directly to CPU memory areas without communication bottlenecks. The module expands system I/O density by mapping up to 32 remote CompoBus/S slave terminals across 128 or 256 discrete I/O points. Integrated hardware diagnostic logic maintains deterministic communication timing, updating internal Participation Flags and Communications Error Flags every bus refresh cycle to detect remote node disconnections or line interference in real time.

Package Contents & Ordering Information

• 1x Omron CJ1W-SRM21 Input Output Control Module
• 1x Removable 5-pin CompoBus/S terminal block unit
• 1x Hardware specification instruction sheet

Field Installation Guidelines

• Subrack Mounting: Slide the CJ1W-SRM21 onto the DIN rail adjacent to the CPU or expansion I/O module. Secure the top and bottom slider locks to maintain solid backplane connector contact.
• CompoBus/S Wiring: Connect dedicated CompoBus/S 2-wire or 4-wire communications cable to the front 5-pin terminal block (BD H, BD L, BS+, BS-).
• Shielding & Grounding: Terminate cable braid shields to the main panel functional earth bar using 360-deg braid shield grounding clamps to maintain high-frequency noise immunity.
• Unit Number Assignment: Set the rotary unit number switches on the front panel to assign the allocated Special I/O Unit memory words before applying backplane power.

Frequently Asked Questions

• Is hot-swapping supported for the CJ1W-SRM21 module during active PLC rack operation?

  No. Main system power to the CJ-series rack must be completely disconnected before removing or inserting the CJ1W-SRM21 module to prevent backplane bus errors.

• How many total CompoBus/S Master Units can be installed on a single CJ-Series PLC system?

  A maximum of 40 CJ1W-SRM21 Master Units can be mounted across the local CPU rack and expansion subracks, subject to CPU memory and power supply limits.

• What memory word allocations are required for the 256-point I/O operating mode?

  In 256-point mode, the module allocates 20 memory words in the Special I/O Unit area: 8 input words, 8 output words, and 4 status diagnostic words.

• How are communications errors and node disconnections reported to the CPU unit?

  The module continuously updates hardware-level Participation Flags and Communications Error Flags mapped directly into the allocated Special I/O status words.

• What signal cable is specified for field connections to the CJ1W-SRM21 terminal block?

  Use dedicated CompoBus/S VCTF 2-wire or 4-wire flat cable, or shielded twisted-pair cable rated for high-speed fieldbus communications.

• How is functional grounding established across the CJ1W-SRM21 module housing?

  Grounding is provided via internal backplane ground pins connected directly to the system power supply unit's Functional Earth (FE) terminal block.

• What node address settings apply when configuring slave devices on the network?

  The module manages node addresses across 8 addresses per mode, supporting up to 32 remote slave devices on a single CompoBus/S trunk line.

• What storage environment limits apply to spare CJ1W-SRM21 control modules?

  Uninstalled spare modules must be stored in original anti-static packaging in ambient temperatures between -20 and +75 deg C in non-condensing environments.