PLCs, Power Supplies & Others

This serial communication module provides versatile connectivity for Yokogawa Centum VP and ProSafe-RS systems. The ALR121 interfaces with external devices through its RS-232-C and RS-422/485 ports. It handles asynchronous data exchange with printers, operator stations, and field instruments effectively. Process engineers choose this module for its dual-port flexibility and robust performance. Its compact single-slot design optimizes rack space utilization.

Technical Specifications Summary

Dual-Port Architecture and Interface Flexibility

The module integrates both RS-232-C and RS-422/485 ports for versatile device connectivity. One port supports standard point-to-point RS-232 communication with peripherals. A second port offers RS-422 or RS-485 operation for multidrop networks. The ALR121 selects RS-422 or RS-485 mode through software configuration. Users configure 2-wire or 4-wire operation for the RS-485 port as needed. This dual-port design eliminates the need for multiple communication modules. Consequently, it reduces system cost and chassis space requirements significantly.

Comprehensive Serial Configuration Options

The module supports extensive configuration parameters for diverse applications. Data rates range from 300 bps up to 38.4 kbps per port independently. Each port handles 7 or 8 data bits with 1 or 2 stop bits flexibly. Parity options include none, odd, even, mark, and space for full compatibility. The ALR121 applies these settings independently to each communication channel. All configuration parameters remain stored in non-volatile memory permanently. This comprehensive parameter set accommodates virtually any serial device standard.

Data Buffering and Flow Control

For reliable data transfer, the module offers 256-byte FIFO buffers per port. These buffers handle transmit and receive operations simultaneously without conflict. The ALR121 supports both hardware and software flow control methods effectively. RTS/CTS handshaking manages data flow for high-speed connections reliably. XON/XOFF software control works with simpler cabling configurations conveniently. The module automatically manages buffer levels to prevent overflow conditions. These features ensure uninterrupted communication even with burst data traffic.

RS-422/RS-485 Long-Distance Capability

The RS-422/RS-485 port enables communication over extended cable distances. This port supports cable runs up to 1200 meters at lower baud rates. The ALR121 accommodates multidrop networks with up to 32 devices on one bus. Users configure termination resistors for network integrity and signal quality. The module supports both 2-wire half-duplex and 4-wire full-duplex modes. This long-distance capability suits distributed plant installations effectively. It also eliminates the need for repeaters in many applications.

Physical Interfaces and Diagnostic Indicators

Two distinct connector types provide access to the communication ports. A 9-pin D-sub connector serves the RS-232-C interface for peripheral connections. A 5-pin terminal block provides RS-422/485 wiring access for field cabling. The ALR121 provides 1500 V RMS isolation between both ports and system logic. Front-panel LEDs indicate power, transmit, receive, and error status per port. These indicators simplify installation verification and ongoing troubleshooting. All connectors include strain relief features for robust field installation.

Mechanical Design and Environmental Specifications

The module features a lightweight construction for simple rack installation. It measures 130 millimeters high, 40 millimeters wide, and 120 millimeters deep. The unit weighs only 0.35 kilograms for convenient handling. Power consumption reaches 4 watts from the +5 V DC backplane supply. Operating temperature spans -10 °C to +55 °C for control room environments. Storage conditions range from -40 °C to 85 °C for shipping protection. Humidity tolerance covers 10% to 90% without condensation affecting circuits. These specifications ensure reliable operation across various industrial settings.

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