RMBA-01-KIT | ABB Bailey | Modbus RTU Adapter Module Field Kit

Product Overview

The ABB RMBA-01-KIT is a Modbus RTU Adapter Module Field Kit designed for ABB ACS800, ACS550, and DCS800 series drives. It provides a galvanically isolated RS-485 interface that enables seamless connection of ABB drives to Modbus serial communication networks. Through the RMBA-01, a drive can be controlled as a Modbus slave device, allowing remote operation, parameter access, and status monitoring from a Modbus master station such as a PLC or SCADA system.

Key Technical Specifications

• Product Type: Modbus RTU Adapter Module
• Series: ABB Drives ACS800 / ACS550 / DCS800
• Product ID: 3ABD64606778
• Alias: RMBA-01
• Communication Protocol: Modbus RTU (asynchronous, half-duplex)
• Physical Interface: Galvanically isolated RS-485
• Bus Topology: Multi-drop
• Maximum Bus Length: 1200 m
• Network Size: Up to 247 stations including repeaters (31 stations + 1 repeater per segment)
• Baud Rates: 600, 1200, 2400, 4800, 9600, 19200 bit/s
• Register Area: 4xxxx holding registers (40001–49999)
• Data Mapping: Drive parameters mapped to 4GGPP (Group GG, Parameter PP)
• Power Consumption: Max 140 mA at 5 V (supplied by RMIO board)
• Enclosure Rating: IP 20
• Dimensions: 95 mm (L) × 62 mm (W) × 34 mm (H)
• Product Net Weight: 0.5 kg
• Product Net Depth / Length: 15.5 cm
• Product Net Height: 5.2 cm
• Product Net Width: 22.5 cm
• Mounting: Inserted into SLOT 1 on RMIO board of the drive; or onto external AIMA-01 I/O Module Adapter
• Connectors: 38-pin parallel bus connector; One 4-pole detachable terminal block (max 1.5 mm²) for fieldbus cable
• Hardware Settings: One DIP switch (S1) for bus termination selection
• Certifications: UL/CSA-approved materials; EMC Standards EN 50081-2 and EN 50082-2
• Estimated Lifetime: ≥ 100,000 hours
• Country of Origin: Finland (FI)
• Customs Tariff Number: 85049099
• UNSPSC: 39122004
• WEEE Category: Product Not in WEEE Scope

Kit Contents

• RMBA-01 Modbus Adapter module
• Two screws (M3 × 8 mm)
• User's manual

Key Features

• Galvanic Isolation: RS-485 interface electrically isolated from drive electronics for noise immunity
• Modbus RTU Protocol: Industry-standard serial communication with broad PLC/SCADA compatibility
• Drive Control Commands: Start, Stop, Run enable, direction, and fault reset via Modbus
• Speed/Torque Reference: Feed motor speed or torque setpoints remotely
• PID Integration: Provide process actual values or references to the drive's internal PID controller
• Status Monitoring: Read drive status, actual values, and parameters in real-time
• Parameter Access: Read and write drive parameters through 4xxxx register area
• Broadcast Write: Simultaneous write to all slave stations on the network
• Built-in Termination: Active bus termination switch (S1) for reliable multi-drop networks
• Diagnostic LEDs: RxD (green), TxD (green), WD/INIT (yellow) for visual status indication

Supported Modbus Function Codes

• 03 (0x03): Read Holding Registers — Reads binary contents of 4X references
• 06 (0x06): Preset Single Register — Writes value to single 4X reference
• 16 (0x10): Preset Multiple Registers — Writes values to sequence of 4X references

Register Mapping

• 40001–40096: Data sets (3 data words per set, e.g., Data word 2.3 = 3rd word in data set 2)
• 40101–49999: Drive parameters (4GGPP format: GG = group number, PP = parameter number)

Diagnostic LED Indicators

• RxD (Green): Blinks when RMBA-01 receives a Modbus message
• TxD (Green): Blinks when RMBA-01 sends a Modbus message
• WD/INIT (Yellow): Lights at power-up; extinguishes after successful drive configuration. Relights if module resets due to power loss or configuration failure

Exception Codes

• 01 (Illegal Function): Unsupported command
• 02 (Illegal Data Address): Address does not exist or is read/write protected
• 03 (Illegal Data Value): Value outside min-max limits or parameter is read-only

Compatible Drives

• ACS800 Standard Application Program (version ASXR7000 or later)
• ACS550 series
• ACQ800 series
• DCS800 series

Applications

• Industrial pump and fan speed control via Modbus network
• Conveyor system drive integration with PLC
• HVAC system remote monitoring and control
• Water/wastewater treatment process automation
• Manufacturing line centralized drive management

Installation Guide

1. Insert RMBA-01 carefully into SLOT 1 on the RMIO board until retaining clips lock into position
2. Fasten two included screws (M3 × 8 mm) to stand-offs for secure mounting and shield grounding
3. Set bus termination switch (S1) to required position — ON for end-of-line devices, OFF for mid-bus devices
4. Connect shielded twisted-pair RS-485 cable (Belden 9841 2-wire or 9842 4-wire recommended) to terminal block X1:
   • A- — Data line A (negative)
   • B+ — Data line B (positive)
   • GND — Signal ground
   • SHLD — Cable shield (connected to chassis ground via screw)
5. Configure drive parameters for Modbus communication:
   • 98.02 — Select communication card: STD MODBUS
   • 98.07 — Select communication protocol: ABB Drives (default)
   • 52.01 — Define station ID: 1–247
   • 52.02 — Define communication speed (baud rate)
   • 52.03 — Define parity: NONE1STOPBIT / NONE2STOPBIT / ODD / EVEN
6. Verify WD/INIT LED extinguishes after configuration (indicates successful setup)
7. Test Modbus communication with master station

Troubleshooting

• WD/INIT LED remains lit:
  • Configuration failed — power cycle the drive
  • Module hardware failure — verify 38-pin connector is properly inserted; contact ABB service
• Control commands not working: Verify RMBA-01 is selected as control source in drive parameters
• No communication: Check Modbus cable connections, termination switch, and station ID/baud rate settings

FAQ

Q: What is the difference between RMBA-01 and RMBA-01-KIT?
A: RMBA-01 is the module itself; RMBA-01-KIT is the complete field kit including the module, mounting screws, and manual.

Q: What drives is RMBA-01 compatible with?
A: ACS800, ACS550, ACQ800, and DCS800 series drives with standard application program ASXR7000 or later.

Q: What is the maximum network size?
A: Up to 247 stations including repeaters, with 31 stations and 1 repeater per segment.

Q: What cable is recommended?
A: Belden 9841 (2-wire) or Belden 9842 (4-wire) shielded twisted-pair RS-485 cable.

Q: Does it support Modbus TCP/IP?
A: No, RMBA-01 supports Modbus RTU serial protocol only. For Ethernet-based Modbus, consider alternative communication modules.

Q: What is the register mapping format?
A: 4GGPP where GG = parameter group number and PP = parameter number within the group (e.g., 40101 = Group 01, Parameter 01).

Q: Can I use broadcast write?
A> Yes, Modbus broadcast write is supported for simultaneous control of multiple drives, but no verification is returned to the master.

Model Selection Tips

• RMBA-01-KIT = Modbus RTU Adapter Field Kit for ABB ACS800/ACS550/DCS800 drives
• Verify drive model and firmware version (ASXR7000 or later for ACS800)
• Confirm Modbus master (PLC/SCADA) supports RTU protocol
• Check network topology — calculate repeater needs for >31 devices per segment
• For Profibus communication, consider RPBA-01 adapter instead
• For DeviceNet, consider RDNA-01 adapter
• For Ethernet/IP, consider alternative Ethernet-based fieldbus modules