Configuring CP1L Modbus RTU Easy Master for 3G3JX and V1000 Drives

This reference walks through commissioning an Omron CP1L CPU as a Modbus RTU Easy Master against a Yaskawa-built 3G3JX (and equivalent V1000) inverter. The same architecture applies to CP1H and CJ1W-SCU serial option boards. The goal is run/stop, forward/reverse, frequency reference, and parameter read/write over RS-485 with the CP1W-CIF11/CIF12 option, plus an optional NS/CX-Designer HMI for operator control.

1. System Overview and Topology

The serial gateway on the CP1L converts Modbus RTU requests from a SCADA/HMI into Modbus RTU to the inverter without requiring a custom protocol macro. The Easy Master functionality ships in the CP1L firmware; no option board is required for the controller side, but a CP1W-CIF11 (RS-422/485) or CP1W-CIF12 (RS-422/485 isolated) must be installed in the right-hand option slot of the CP1L.

2. Supported Modbus Function Codes on the 3G3JX

The 3G3JX inverter responds to the following Modbus function codes. Implement only what you need; most projects use 03 and 10.

The minimum functional set for run/stop and frequency reference uses only 03 (read) and 10 (write multiple registers). Use 05 or 0F for bit-level control when you want direct mapping to discrete PLC outputs.

3. Hardware Wiring

3.1 CP1W-CIF11 / CIF12 DIP Switch Configuration

Set the on-board DIP switches before powering the PLC. Default mode is RS-232C; the switches below select RS-422/485 2-wire mode needed for the 3G3JX.

3.2 3G3JX Communication Terminal Wiring

The 3G3JX serial port uses a removable screw terminal block. Pinout for RS-485 2-wire (Modbus RTU):

4. 3G3JX Parameter Configuration

Configure the inverter before attaching it to the network. The exact parameter number is the same on Yaskawa V1000 (C0xx block) and 3G3JX.

After writing parameters the inverter typically requires a power cycle for communication settings to take effect. C076 = 2 prevents nuisance trips while you are debugging the link; tighten this to 1 (coast to stop) or 3 (decelerate) before handover.

5. CP1L Modbus Easy Master Setup

CX-Programmer exposes the Easy Master block as a function block on port 2 when the option board is recognised. Configure the port first.

5.1 PLC Port Settings

Selecting Serial Gateway routes any Modbus RTU frame sent to the PLC's serial port through to port 2 untouched, which is what enables direct SCADA/Master traffic and Easy Master traffic to reach the inverter.

5.2 PMCR Instruction and Source Words

The Easy Master function uses the standard PMCR instruction. The protocol macro area is pre-loaded with the Modbus master protocol. The relevant control words are:

The first five DM words beginning at D32300 contain the request to transmit. A typical Write Single Register (function 06) request to set Accel time on node 1:

When sending a Write Multiple Registers (function 10) to set the frequency reference, populate the command block with function code #0010, the starting register address (for frequency reference this is 0x0001 in the command area), the register count, and the data bytes in subsequent words. The exact layout is documented in the CP1L Easy Master reference; always subtract 1 from any address listed in the 3G3JX manual when entering it into the source block.

5.3 Sample Ladder

| Run Enable (W0.00) |
        +---[ ]---[PMCR C1=0 C2=0 S=D32300 D=D32350 ]---(W0.01 Done)---
        |        |
        |        +---[W0.01]---[MOV #1 D32300] (node)
        |        +---[W0.01]---[MOV #6 D32301] (function code)
        |        +---[W0.01]---[MOV #00C8 D32302] (parameter addr - 1)
        |        +---[W0.01]---[MOV #000A D32303] (value)
        +---[ ]---[A640.00]                         (Start request)

The example above shows the structure, not the exact rung order. In production code you would normally pre-populate D32300 through D32304 with MOV instructions at first scan and only toggle the PMCR rung on a transition.

6. Reading the Frequency Reference and Status

Function code 03 reads holding registers. To read the current output frequency on the 3G3JX, request register address 0x1001 (decimal 4097). After subtracting 1, the Modbus register passed in the request is 4096.

Reading the drive status word (run, direction, fault) uses coil addresses listed in the inverter manual. Coil address 0x0001 = run command, 0x0002 = reverse direction, 0x0003 = external fault reset, and so on. Subtract 1 from every address you read out of the manual.

7. CX-Designer HMI Integration

The same Easy Master traffic is visible to a CX-Designer NS panel or any OPC client that speaks Modbus TCP/RTU to the CP1L's serial gateway. To run a virtual NS against the live PLC:

1. Build the project in CX-Designer against the target NS type.
2. From the Tools menu launch CX-Designer Simulation. The simulator binds to the PLC selected in CX-Programmer.
3. Confirm the simulator is connected by toggling a bit registered in the project; the bit state should appear in the PLC's input/output monitor within one scan.
4. Wire the run and frequency reference buttons to PLC addresses that the Easy Master program converts into Modbus requests to the 3G3JX. The simulator will then issue real traffic against the live inverter.

The simulator cannot open a serial gateway if the NS screen's host connection settings disagree with the CX-Programmer port settings (baud, parity, stop bits). Match the CX-Designer NS project host parameters exactly to those in section 5.1.

8. Using CX-Drive for Parameter Backup and Restore

Omron's CX-Drive tool can parameterise the 3G3JX over Modbus RTU even though the drive is a Yaskawa design. CX-Drive loads an EDS/IODD-style object dictionary that mirrors the parameter list. The risk of overwriting drive firmware through a parameter upload is zero: CX-Drive only writes parameter values, never firmware. If a parameter upload appears to break communications afterward, the cause is usually a serial-port parameter (C071, C072, C074) being overwritten with a value that disagrees with the master.

Recovery steps after a botched upload:

1. Disconnect the network cable so the PLC stops talking.
2. On the inverter keypad navigate to the communications block (group C) and verify A001, A002, C070, C071, C072, C074, C075.
3. Reset to the values in section 4 above. DriveWizard Plus or the keypad can do this; the inverter does not require a firmware reflash.
4. Power-cycle the inverter to commit changes.
5. Reconnect RS-485 and run a known-good Modbus request (function 03 to read frequency) to verify.

9. SCADA Integration via Serial Gateway

For a direct PC-to-inverter Modbus link, leave the PLC out of the path and use CX-Driver with a USB-to-RS-485 converter, or use OPC KEPware with the Omron/Yaskawa driver. The Modbus node address, baud, and parity settings are identical to those in section 4. Use one Modbus master per bus at a time; the Easy Master code on the CP1L and an external SCADA master cannot share the bus without an arbitrator.

10. Troubleshooting Matrix

11. Verification Procedure

1. Power-cycle the inverter after writing any C0xx parameter.
2. From CX-Programmer, force a function 03 read of the output frequency register. Confirm the response word returns a non-zero scaled value when the drive is running.
3. Issue a function 06 write of register 0x0001 (frequency reference) with a small value (e.g. 100 = 10.0 Hz). Confirm the drive accelerates to the commanded frequency.
4. Use a function 05 write to coil 0x0001 (run forward). Confirm the drive starts. Use function 05 write of coil 0x0001 with value 0 to stop.
5. Launch the NS simulator and exercise the run/stop/speed screen end-to-end.
6. Set C076 back to the required production value (1 or 3) once stable.

12. References

• Omron 3G3JX Inverter Brochure (Europe)
• Omron 3G3JX Simple Compact Inverter Features

FAQ