Yaskawa V1000 Modbus RTU: Register Map and Frequency Reference

Yaskawa V1000 Modbus RTU: Register Map and Frequency Reference Programming

The Yaskawa V1000 series compact AC drive supports Modbus RTU over an isolated RS-485 interface, allowing a master controller (PLC, HMI, PC, or microcontroller) to command frequency, start/stop, read status, and modify most of the drive's 400+ parameters. The most common commissioning error is writing the frequency reference to the wrong Modbus holding register. This reference covers the V1000 register map, addressing conventions, the canonical d1-01 Frequency Reference 1 location at 0x0280, RS-485 wiring, parameter setup, and a troubleshooting matrix for the faults encountered during integration.

1. Prerequisites

Before writing a single holding register, confirm the following:

• Drive model: Yaskawa V1000 (CIMR-VU series). The V1000 is shipped with on-board RS-485 on terminals S+, S-, and IG. No option card is required.
• Firmware: V1000 drives with U-spec (CIMR-VU) firmware ship with Modbus RTU enabled out of the box. Confirm by reading parameter H5-01 at the keypad.
• Hardware: USB-to-RS-485 converter (FTDI FT232R/FT4232H based converters are recommended; avoid CH340 clones for industrial use), twisted-pair shielded cable (Beldan 3106A or equivalent), 120 Ω termination resistor at the bus ends only.
• Software: modpoll (from ModbusTools), Simply Modbus Master, pymodbus (Python), or any Modbus RTU master. modpoll is the fastest path to verify a register before writing PLC code.
• Termination: At least one bus termination (120 Ω across S+/S-) is required for 19200 baud and above. Place a second 120 Ω resistor at the physical far end of the bus when the cable run exceeds 10 m.

2. RS-485 Hardware Wiring

The V1000 exposes RS-485 on control terminal block TB1:

Wire the master D+ to the drive S+ and master D− to S−. Keep the differential pair twisted; the shield should be clamped at SC on the drive end and left floating at the master end unless the master's documentation specifies bonding.

3. Drive Parameter Configuration for Modbus Control

Five parameters must be configured before Modbus writes will produce motion. Configure them from the keypad or by writing to their Modbus holding registers.

4. Modbus Register Map Overview

The V1000 Modbus map is partitioned into four functional regions:

1. Monitor region (read-only): 0x0001 – 0x0020. Contains drive status, output frequency (0.01 Hz units), output current (0.1 A), output voltage (1 V), DC bus voltage (1 V), and the active fault word.
2. Command region (read/write): 0x0280 – 0x02AF. Contains the most-used writable parameters: d1-01 through d1-17 frequency references, acceleration/deceleration ramps, and other frequently changed settings.
3. Configuration region (read/write): 0x0300 – 0x04FF. All other drive parameters, addressable by their four-digit number. b1-01 is at 0x0301, H5-01 is at 0x04A9, etc.
4. Function-code run command: 0x0001 (bit 0 = forward, bit 1 = reverse). Some V1000 manuals list a run command register at 0x0001; the V1000 A-spec uses 0x0001 for a different purpose. Always confirm against the manual revision.

5. d1-01 Frequency Reference Register

The most-commonly written Modbus register on a V1000 is the Frequency Reference 1, parameter d1-01. Its address is 0x0280 (640 decimal).

6. PDU vs Protocol Addressing

Modbus addresses can be expressed two ways:

• PDU (Protocol Data Unit) address: The zero-based address used in the raw frame. For d1-01 this is 0x0280 = 640.
• Protocol (or "Modbus convention") address: The one-based, 5-digit "register number" found in some Yaskawa manuals. For d1-01 this is 0x1281 (4xxxx-range) = 4737.

modpoll's -0 flag uses PDU addressing; -1 uses protocol addressing. When using modpoll against a V1000, always pass -0:

modpoll.exe -m rtu -p none -1 -0 -r 640 -b 9600 -a 1 com3 12000

Breakdown:

7. Raw Frame Reference: 0x10 Write Single Register

Function code 0x10 (16 decimal, Write Multiple Registers) is required for any 16-bit Modbus write. The following frame was captured on a V1000 setting 120.00 Hz:

01 10 02 80 00 01 02 2E E0 86 78

Decoded byte by byte:

The drive's reply on success is:

01 10 02 80 00 01 40 E0

Note the echoed starting address 02 80 and quantity 00 01 — this is the standard 0x10 acknowledgement.

8. CRC-16 Calculation

Modbus RTU uses CRC-16/MODBUS (polynomial 0xA001, reflected 0x8005) with the low byte transmitted first. Python implementation:

def crc16_modbus(data: bytes) -> bytes:
    crc = 0xFFFF
    for byte in data:
        crc ^= byte
        for _ in range(8):
            if crc & 0x0001:
                crc = (crc >> 1) ^ 0xA001
            else:
                crc >>= 1
    return bytes([crc & 0xFF, (crc >> 8) & 0xFF])

# Usage for the frame above:
frame = bytes.fromhex("01 10 02 80 00 01 02 2E E0".replace(" ", ""))
tx = frame + crc16_modbus(frame)
# tx = 01 10 02 80 00 01 02 2E E0 86 78

Most tools (modpoll, pymodbus, libmodbus) compute the CRC automatically. If you are implementing a custom master, use a runtime-checked polynomial — never reuse a "works on the bench" CRC table without validation against a known vector.

9. Reading Back Status and Output Frequency

Function code 0x03 (Read Holding Registers) or 0x04 (Read Input Registers) reads the monitor region. To read the output frequency and drive status:

modpoll.exe -m rtu -p none -1 -0 -r 1 -c 2 -b 9600 -a 1 com3

This reads registers 0x0001 (output frequency) and 0x0002 (output current). To read the active fault code:

modpoll.exe -m rtu -p none -1 -0 -r 3 -c 1 -b 9600 -a 1 com3

Common V1000 fault codes returned at register 0x0003:

10. Run Command via Modbus

Yaskawa V1000 supports a run command via function code 0x05 (Write Single Coil) or, more commonly, via 0x10 with a control word register. For the V1000, the most portable approach is to use the run command bits in the control word at register 0x0001 (varies by manual revision). However, the documented cross-platform method is to drive terminals: with b1-02 = 1 (terminal run), a Modbus-controlled PLC or HMI can close digital inputs S1 (forward) and S2 (reverse) using a 24 V signal. For pure Modbus run/stop, set b1-02 = 2 and issue 0x10 writes to the control register at 0x0001.

modpoll.exe -m rtu -p none -1 -0 -r 1 -b 9600 -a 1 com3 1   # Start forward
modpoll.exe -m rtu -p none -1 -0 -r 1 -b 9600 -a 1 com3 0   # Stop

Safety: The V1000 will start the motor the instant the run command and a non-zero frequency reference are present. Always verify the b1-03 stop method (ramp, coast, DC brake) and b1-05 minimum output frequency before commissioning.

11. Alternative Master Tools

12. pymodbus Example: Continuous Speed Sweep

After commissioning, the following Python script ramps the drive through 0–60 Hz in 1 Hz steps. It assumes b1-01 = 2, b1-02 = 2, and a run command held high via terminal S1.

from pymodbus.client import ModbusSerialClient
import time

client = ModbusSerialClient(
    port='COM3', baudrate=9600, parity='N', stopbits=1, bytesize=8, timeout=1
)
client.connect()

try:
    for hz in range(0, 61):
        value = hz * 100  # 0.01 Hz units
        client.write_register(0x0280, value, slave=1)
        print(f"Requested {hz:2d} Hz (reg 0x0280 = {value})")
        time.sleep(0.5)
    client.write_register(0x0280, 0, slave=1)
finally:
    client.close()

13. Troubleshooting Matrix

14. Enter Command and Parameter Persistence

The V1000 buffers parameter writes to RAM. To commit to EEPROM, write to the Enter command register:

15. Modbus TCP/IP Variant

Yaskawa also offers a Modbus TCP/IP variant, used when interfacing to factory MES/ERP systems or when the controller is Ethernet-only. The same register map (0x0001, 0x0280, etc.) applies, but the framing uses TCP port 502 and the slave address is encoded in the MBAP header. The protocol is described on the Yaskawa Modbus TCP/IP product page, and is supported via the SI-EN3 / SI-EN3D Ethernet option card on the V1000. Most of the register-map content above is identical between the RTU and TCP/IP variants.

16. Field Commissioning Checklist

1. Verify input voltage and motor nameplate (V, FLA, RPM, kW) match the V1000 rating.
2. Wire S+, S−, and IG to the master. Add 120 Ω at both physical ends.
3. From the keypad, set b1-01 = 2, b1-02 = 2, H5-01 = 1, H5-02 = 3 (9600), H5-03 = 0 (none), H5-09 = 2.0, H5-10 = 1 (coast on loss).
4. Run an autotune (T1-01 = 1 for rotational, 2 for stationary).
5. Use modpoll to read register 0x0000 (status) and confirm normal response.
6. Write 0x2EE0 (12000) to register 640 (d1-01). Issue a run command. Verify motor accelerates to ~120 Hz if E1-04 allows; otherwise scale to your maximum frequency.
7. Read register 0x0003 to confirm no active faults.
8. Commit parameters with write to 0x0900 = 1.

FAQ