FX3U-ENET-L is a dedicated Ethernet communication module for Mitsubishi Electric’s MELSEC FX3U and FX3UC series programmable logic controllers, enabling TCP/IP and UDP/IP network connectivity for SCADA integration, remote programming, and data exchange with higher-level systems. Unlike the FX3U-ENET (standard variant), the FX3U-ENET-L supports a broader range of open Ethernet protocols and is specifically designed for larger-scale network architectures where multiple FX3U nodes must communicate simultaneously with HMI systems, data historians, and MES platforms. The FX3U-ENET-L is available through Atlantech Drives — quote within 24-48 hours, worldwide express shipping, 12-month warranty.
What Is the FX3U-ENET-L?
The FX3U-ENET-L is a left-side special function module that mounts directly onto the FX3U or FX3UC CPU base unit. The «L» suffix distinguishes it from the standard FX3U-ENET by indicating enhanced protocol support and an increased number of simultaneous open connections. Where the FX3U-ENET supports up to 8 open connections, the FX3U-ENET-L supports up to 16 simultaneous TCP/IP or UDP/IP connections, making it the correct choice for installations where the PLC must serve data to multiple concurrent clients — such as a GOT HMI, a SCADA server, a web monitoring client, and a remote GX Works2 programming session all active simultaneously. The module connects to the FX3U CPU via the dedicated left-side bus, consuming no standard I/O extension slots. It is powered from the main FX3U power supply unit and requires no external 24 V DC supply.
Key Technical Specifications
- Compatible Base Units: FX3U, FX3UC (requires FX3UC-1PS-5V for power)
- Communication Standard: IEEE 802.3 (10BASE-T / 100BASE-TX)
- Connector: RJ45, Auto MDI/MDI-X
- Protocols Supported: TCP/IP, UDP/IP, SLMP (MC Protocol), FTP client/server
- Simultaneous Open Connections: Up to 16
- IP Address Setting: GX Works2 parameter or rotary switch (fixed IP)
- Transmission Speed: 10/100 Mbps (auto-negotiation)
- Data Buffer: 4,096 bytes per connection (receive/send)
- Fixed Buffer Communication: Supported (procedure/no-procedure)
- Random Access Buffer: Supported (word/bit device access)
- FTP Server Function: Supports data logging file retrieval from FX3U-CF-ADP
- Power Consumption: 5 V DC, 150 mA (from FX3U bus)
- Operating Temperature: 0 °C to 55 °C
- Dimensions: 55 × 90 × 87 mm (W × H × D)
- Weight: Approx. 220 g
Architecture & Design Overview
The FX3U-ENET-L is architecturally a bridge between the FX3U’s internal device memory (D registers, M relays, Y outputs, etc.) and the Ethernet network. Communication is handled through two primary mechanisms: Fixed Buffer Communication, where the FX3U exchanges pre-defined data packets with a remote client using FROM/TO instructions in the ladder program; and Random Access Buffer Communication, where a remote SCADA or HMI system reads and writes FX3U device addresses directly over SLMP (Seamless Message Protocol, formerly known as MC Protocol 3E/1E frames). The SLMP interface is the most commonly used mode for SCADA integration, as it is supported natively by most industrial SCADA packages (Wonderware, Ignition, Citect, iFix) without requiring OPC DA/UA middleware. The FTP client function of the FX3U-ENET-L allows the PLC to push data logging CSV files (generated by the FX3U-CF-ADP CompactFlash adapter) to a remote FTP server automatically on a time-triggered basis, enabling lightweight MES data collection without a dedicated data gateway device. Network configuration is performed entirely within GX Works2 under the «Ethernet Module» parameter tab — no separate configuration software is required, and parameters are written to the module at program download.
Installation Advice
The FX3U-ENET-L must be mounted to the left side of the FX3U CPU unit before any right-side extension modules — it occupies the dedicated left-side expansion port and cannot be repositioned in the extension chain. Maximum of one FX3U-ENET-L can be connected per FX3U CPU. When assigning an IP address, choose between parameter-based assignment in GX Works2 (recommended for most installations, as it allows IP changes without hardware access) or hardware switch assignment using the module’s rotary switches (useful for rapid replacement without a programming PC). In network environments with managed switches, configure the switch port to which the FX3U-ENET-L connects as an access port (untagged VLAN) — the module does not support VLAN tagging. For SCADA polling intervals faster than 100 ms, use UDP/IP rather than TCP/IP to avoid the TCP handshake overhead on high-frequency data acquisitions. Always assign a static IP address rather than DHCP; DHCP is supported but IP changes between power cycles can disrupt SCADA driver connections and require manual reconfiguration of the client application.
Frequently Asked Questions
Q: Can the FX3U-ENET-L be used to program the FX3U remotely over Ethernet from GX Works2?
A: Yes. GX Works2 supports direct Ethernet connection to the FX3U-ENET-L using the SLMP (MC Protocol) transport. In the GX Works2 connection settings, select «Ethernet» as the interface, enter the module’s IP address and port 5007 (default MELSOFT port), and the software will connect to the CPU for online monitoring, program upload/download, and device watch operations exactly as it would over USB.
Q: Is the FX3U-ENET-L compatible with the older FX3G or FX3S CPU series?
A: No. The FX3U-ENET-L is mechanically and electrically specific to the FX3U and FX3UC left-side bus. The FX3G and FX3S series use a different left-side expansion architecture and are not electrically compatible with this module. For FX3G Ethernet connectivity, Mitsubishi offers the FX3G-ENET-ADP adapter module instead.
Q: How many GOT HMI panels can simultaneously connect to a single FX3U-ENET-L?
A: With its 16 simultaneous connection capacity, the FX3U-ENET-L can theoretically support up to 16 concurrent TCP sessions. In practice, Mitsubishi recommends a maximum of 4–6 GOT panels per module to maintain responsive refresh rates, as each active GOT connection generates continuous polling traffic that competes for the module’s processing bandwidth.
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