YOKOGAWA AALR121-S00

Technical Specifications Interface: RS-422 (4-wire, point-to-point) and RS-485 (4-wire, multipoint) Number of Ports: 2 independent serial ports Connection Method: point-to-point (RS-422), multipoint (RS-485) Communication Function: half-duplex Synchronization: start-stop synchronization Transmission Speed: 1200, 2400, 4800, 9600, 19200, 38400 bps Transmission Code: ASCII or binary Character Length: 7 or 8 bits (fixed to 8 bits for Modbus slave) Stop Bit Length: 1 or 2 bits Parity: none, even, or odd Transmission Distance: maximum 1200 m total extended length (RS-485); 15 m for RS-422 short-haul Lag Time After Transmission: 1 ms Current Consumption: 0.5 A Weight: approximately 0.34 kg Certification: CE Place of Origin: Indonesia

Functional Features Two independent serial ports support simultaneous connection to two different subsystems or device networks. RS-485 multipoint topology allows up to 32 devices per segment without repeaters. Modbus slave function enables third-party PLCs and SCADA systems to read and write DCS data. Subsystem communication function supports Yokogawa FA-M3 PLCs and other proprietary serial protocols. Configurable baud rate, parity, and data framing match a wide range of third-party devices.

Application Scenarios Integration of weigh feeders, belt scales, laboratory analyzers, barcode systems, UPS units, and intelligent motor controllers into the CENTUM DCS. Connection of Modbus RTU devices, PLCs, and RTUs for data acquisition and supervisory control. Used in oil and gas, chemical, power, water, and manufacturing plants where serial devices must coexist with the DCS.

Performance Parameters Maximum nodes per RS-485 segment: 32 (without repeater) Communication mode: half-duplex asynchronous Data buffer: sufficient for cyclic and message-based transactions Operating temperature: 0 to +55 °C Storage temperature: -40 to +70 °C Humidity: 5 to 95% RH non-condensing Isolation: port-to-system galvanic isolation

Material Composition Flame-retardant UL 94 V-0 plastic housing. Gold-plated backplane and terminal connectors. Glass-epoxy PCB. RS-422/485 transceiver ICs with ESD protection. Internal DC-DC isolation converters.

Structural Features Single-slot plug-in module for FIO node racks. Front panel houses two DB-9 or terminal-block serial connectors (depending on style), port status LEDs, and a fault LED. Internal circuitry includes two independent UART channels, isolation barriers, and line drivers with fail-safe biasing. Rear backplane connector carries ESB bus signals and power.

Working Principle The FCS sends and receives serial data through the module via the ESB bus. The module’s UART converts parallel bus data into asynchronous serial frames and drives the RS-422/485 transceiver. In half-duplex mode, the transmitter and receiver share the same physical pair, with a 1 ms turn-around lag after transmission before reception resumes. For Modbus slave operation, the module decodes Modbus RTU frames, maps register addresses to DCS data items, and responds with requested data or executes write commands.

Installation Requirements Install the module in a compatible FIO node rack (AFV10, AFV30, AFV40, AFF50, ANB10, ANB11, or ANR10). Connect serial devices using shielded twisted-pair cable. For RS-485 multipoint, install 120 Ω termination resistors at both ends of the bus segment. Set device addresses and baud rates to match the configuration in the CENTUM engineering software. Keep total cable length within 1200 m. Ground the cable shield at one end only.

Usage Precautions Do not mix RS-422 and RS-485 devices on the same port. Ensure only one device transmits at a time in half-duplex RS-485 to avoid bus collisions. Install termination resistors at the physical endpoints of every RS-485 segment. Use shielded cable and avoid routing near high-voltage or high-frequency lines. Configure Modbus register mapping carefully to prevent data type mismatches. Do not exceed 32 devices per segment; use repeaters for larger networks.