Links an FA-M3 controller to Modbus-compatible instruments and controllers over RS-422/RS-485.
Product Profile
F3LC31-2F is the Yokogawa FA-M3 Modbus interface module. It provides one isolated port conforming to EIA RS-422-A / RS-485.
The module supports both Modbus RTU and Modbus ASCII and can operate as a master communicating with third-party slaves or as a slave responding to an external master.
Two-wire and four-wire arrangements are supported with half-duplex transmission and shielded twisted-pair cabling.
Technical Data
| Manufacturer | Yokogawa |
|---|---|
| Exact model | F3LC31-2F |
| System family | FA-M3 |
| Interface | EIA RS-422-A / RS-485 |
| Ports | 1 isolated port |
| Protocols | Modbus RTU and Modbus ASCII |
| Operating roles | Master or slave |
| Transmission mode | Half-duplex, 4-wire or 2-wire |
| Transmission rates | 300, 600, 1200, 2400, 4800, 9600, 14400, 19200, 28800, 38400, 57.6k and 115.2 kbps |
| Maximum distance | 1200 m total |
| Transmission medium | Shielded twisted pair, AWG20 to AWG16 |
| Terminal block | 6-point, M3.5 screws |
| External dimensions | 28.9 × 100 × 83.2 mm |
System Role
Acts as a Modbus master for polling market-standard slave devices.
Acts as a Modbus slave for integration under another vendor’s master controller.
Provides an isolated serial path for electrically separated industrial communications.
About IndustryParts
https://www.industryparts.com/Serial-network settings remain part of the record
IndustryParts prepares F3LC31-2F quotations with the wiring mode, protocol format and station map so the replacement can be commissioned predictably.
- RTU/ASCII mode recorded
- Two-/four-wire topology checked
- Station map requested
Compatibility
- No restriction is specified on the FA-M3 CPU module type used with F3LC31-2F.
- Use the correct two-wire or four-wire terminal arrangement from Yokogawa documentation.
- For two-wire operation, short SDA to RDA and SDB to RDB at the terminal block as documented.
- Confirm baud rate, RTU/ASCII format, station address, parity and timeout settings at both ends.
Applications
- FA-M3 integration with drives, meters, analyzers and remote I/O using Modbus.
- Brownfield serial-network expansion where an isolated RS-485 port is required.
- Gateway duties between an FA-M3 application and a third-party Modbus master or slave.
FAQ
Q01Can F3LC31-2F operate as both Modbus master and slave?
Yes. Yokogawa documents both roles, but the selected mode and message handling must be configured consistently with the application.
Q02What network record should accompany an F3LC31-2F enquiry?
Provide CPU and base-unit models, slot, wiring type, baud rate, RTU or ASCII selection, parity, station map, cable length and current diagnostics.
Q03What changes when F3LC31-2F is wired for two-wire RS-485?
SDA must be connected to RDA and SDB to RDB at the module terminal block; confirm bias, termination and grounding for the entire network.
Q04How should intermittent F3LC31-2F communication be investigated?
Review shielding, termination, duplicate addresses, baud and parity settings, timeout design, cable length and error counters before replacing the module.
Q05What proves an F3LC31-2F replacement is ready?
Confirm the exact model, restored parameters, stable communications with every required station, clean error statistics and successful application message testing.
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