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Description
Yokogawa ALR121-S00 Serial Communication Module
Configured for serial data exchange in Yokogawa CENTUM VP and CENTUM CS 3000 systems, the Yokogawa ALR121-S00 (ALR121 Serial Communication Module) provides direct electrical interfacing over RS-422/RS-485 physical layers. It executes asynchronous start-stop data transfer for subsystem integration at defined baud rates.
Hardware Specifications
Parameter
Specification
Brand
Yokogawa
Model
ALR121-S00
Origin
Japan
Weight
0.34 kg
Dimensions
Not specified
Operating Temp
0 to 50 degC
Power Consumption
0.5 A max
Communication Ports
2 independent
Interface Standard
RS-422 / RS-485
Transmission Code
Binary
Synchronization
Asynchronous (start-stop)
Communication Mode
Half-duplex
Max Cable Length
1200 m
Process Bus Integration and Channel Isolation
The ALR121-S00 supports channel-to-channel isolation to prevent ground loop formation between subsystems. Integration occurs through deterministic backplane bus transactions within the Field Control Station (FCS). Electrical isolation is maintained between each serial port and the DCS backplane to suppress transient propagation from connected field devices.
Frequently Asked Questions
Q: Does the ALR121-S00 support hot-swapping?
A: Yes. The module can be replaced online in a powered FCS node without interrupting system operation, provided redundancy is configured.
Q: What is the maximum number of devices per RS-485 port?
A: Each port supports up to 31 devices in multi-drop configuration under RS-485 signaling constraints.
Q: Can both ports operate at different baud rates?
A: Yes. Each port can be independently configured for speed, parity, and protocol settings.
Field Installation Guidelines
Install the module in designated FCS I/O slots only. Use shielded twisted-pair cable for all serial connections. Terminate shield grounds at the DCS side using approved grounding bars; do not connect shields at device ends to avoid ground loops. Observe maximum cable length limits to maintain signal integrity. For redundant configurations, ensure both modules share identical firmware revisions before commissioning.
