The Omron CJ1W-CRM21, also cataloged as the CJ1W-CRM21 CompoNet Master Unit, operates as a dedicated hardware component for high-speed fieldbus I/O bus management and slave node data cyclic exchanging within CJ Series PLC backplanes.

Architecture Classification & Functional Design

The Omron CJ1W-CRM21 module interfaces directly with CJ Series system bus slots, acting as a specialized bus controller:

• CJ1W: Dedicated module series platform for Omron CJ1G, CJ1M, CJ2M, and CJ2H programmable controllers.
• CRM: Designation for CompoNet fieldbus protocol master hardware.
• 21: Specific hardware release iteration for high-density I/O allocation and communication power monitoring.
• Unit Classification: Mapped as a Special I/O Unit using hardware rotary switches to define unit numbers.

Physical and Electrical Specifications

Deterministic Network Management & Bus Synchronicity

The unit coordinates deterministic networks across CompoNet remote slaves, handling rapid cyclic I/O refreshes and message communications simultaneously. Backplane bus communication velocity allows seamless memory transfer between the controller CPU and remote slave registers without impacting scan timing. Firmware flash compatibility ensures persistent network layout retention and predictable boot execution across power recycling events.

Package Component List

• 1 x Omron CJ1W-CRM21 CompoNet Master Unit
• 1 x CompoNet communication power supply connector assembly
• 1 x Panel installation sheet

Field Termination & Grounding Rules

• System Power Isolation: Always disconnect the PLC backplane power supply before inserting or removing the module from the rack slot.
• Communication Cable Shielding: Use specified CompoNet round cables or flat cables. Ground the cable shield wire at a single point to panel ground.
• Power Supply Monitoring Wire: Ensure proper polarity when wiring the external communications power supply to enable real-time ON/OFF monitoring.
• Terminal Fastening: Secure communication cable connector screws completely to resist panel vibration up to 196 m/s2 acceleration limits.

Frequently Asked Questions

• What causes the unit to flag a communication power error?

  The module actively monitors the communications power supply connector. If 24 VDC external bus power drops below threshold levels, an ON/OFF fault is registered.

• Is hot-swapping supported for the CJ1W-CRM21 on a live CJ rack?

  No. Removing or inserting the unit while the CJ backplane power supply is turned on will cause a bus communication error and halt execution.

• How much current does the unit draw directly from the PLC backplane?

  The unit draws a maximum current of 400 mA at 5 VDC directly from the internal PLC rack power supply.

• What is the maximum current capacity allowed through the communications power connector?

  The communications power supply connector supports a maximum current capacity of 5 A for downstream network node power distribution.

• Can the unit operate in any standard slot on a CJ-series expansion rack?

  Yes. The unit can be placed in standard Special I/O slots on CJ-series CPU Racks or Expansion Racks, provided power supply ratings are met.

• How is the module identified within the PLC memory mapping table?

  The module is assigned a Special I/O Unit number from 0 to 95 via front-panel rotary switches to allocate memory space in CPU words.

• Does the CJ1W-CRM21 require separate external power for its logic operations?

  Internal logic runs on 5 VDC backplane power, but external power is required across the network connector to drive fieldbus transceiver circuits.

• How does the module handle high electrical noise in harsh environments?

  The unit features integrated protection conforming to IEC 61000-4-4 standards, withstanding fast transient bursts up to 2 kV on power lines.