The QJ71GP21-SX is Mitsubishi Electric’s CC-Link IE Controller Network master/local module for the MELSEC-Q programmable controller series using single-mode optical fibre transmission — providing a 1 Gbps deterministic industrial Ethernet network for high-speed, long-distance inter-PLC communication between MELSEC-Q systems in large-scale distributed control architectures. As the single-mode fibre variant of the CC-Link IE Controller Network module family, the QJ71GP21-SX supports transmission distances of up to 10 km between stations, making it the preferred specification for campus-wide manufacturing facilities, multi-building process plants, and offshore or remote installations where the inter-controller distance exceeds the 550 m limit of the multimode fibre QJ71GP21S-SX. In stock at Atlantech Drives. Request your quote within 24-48 hours with worldwide shipping and 12-month warranty.
What Is the QJ71GP21-SX?
The QJ71GP21-SX is a MELSEC-Q series intelligent communication module implementing CC-Link IE Controller Network — Mitsubishi Electric’s 1 Gbps fibre-optic industrial network standard designed for deterministic, high-speed data exchange between PLC controllers at the controller level of the automation hierarchy, as distinct from CC-Link IE Field Network which connects PLCs to remote I/O stations. In a CC-Link IE Controller Network, each station shares a cyclic data area (link registers LW and link relays LB) with all other stations on the ring, enabling any controller to read any other controller’s data without point-to-point communication programming. The QJ71GP21-SX operates as either a network master station (controlling network token passing and managing cyclic data refresh) or a local station (participating in cyclic data exchange as a peer), with the operating mode configured via GX Works2 network parameters. Up to 120 stations can share a single CC-Link IE Controller Network ring, with a total cyclic data capacity of 16,384 link relays (LB) and 8,192 link registers (LW) per network.
Key Technical Specifications
- Model: QJ71GP21-SX
- Network: CC-Link IE Controller Network
- Transmission Speed: 1 Gbps
- Transmission Medium: Single-mode optical fibre (LC connector)
- Maximum Station-to-Station Distance: 10,000 m (10 km)
- Maximum Stations per Network: 120
- Cyclic Data Capacity: LB: 16,384 points; LW: 8,192 points
- Transient Data: Supported (up to 960 bytes per request)
- Topology: Ring (dual loop for redundancy)
- Network Redundancy: Automatic loop-back on single cable fault
- Current Consumption (5 VDC internal bus): 0.90 A
- Operating Temperature: 0°C to 55°C
- Compatible CPUs: All MELSEC-Q Universal model and H-model CPUs
- Weight: Approx. 0.30 kg
Compatibility & System Integration
The QJ71GP21-SX is compatible with all MELSEC-Q series CPU modules and integrates with GX Works2 and GX Works3 for network parameter configuration and online monitoring. In a multi-vendor CC-Link IE Controller Network, the QJ71GP21-SX can communicate with other Mitsubishi MELSEC platforms — including MELSEC iQ-R (RJ71GP21-SX), MELSEC-L (LJ71GP23-SX), and MELSEC-Q (QJ71GP21-SX/QJ71GP21S-SX) — that implement the same CC-Link IE Controller Network standard, enabling mixed-platform distributed control architectures. The module supports both cyclic communication (for continuous, deterministic data exchange between station link devices) and transient communication (for on-demand data requests to specific stations, such as reading CPU device values or writing parameter data to remote modules). CC-Link IE Controller Network’s ring topology provides inherent network redundancy — if a single fibre cable between two stations is severed, the network automatically reconfigures as an open-loop within approximately 0.5 seconds, maintaining communication to all stations except those directly adjacent to the break point. For systems requiring zero-interruption fault tolerance, a dual-ring configuration with the QJ71GP21-SX connected to two independent fibre rings provides full redundancy.
Installation Advice
Single-mode fibre installation for the QJ71GP21-SX requires greater care than multimode fibre due to the smaller core diameter (9 µm versus 50/62.5 µm for multimode) that is more sensitive to connector contamination and bend radius violations. Always clean LC fibre connectors with an approved fibre optic cleaning tool before insertion — a single fingerprint on the connector endface can increase insertion loss by 3–5 dB, sufficient to cause intermittent link errors on a 10 km span. Inspect connectors under fibre inspection microscope before and after cleaning to confirm the endface is free of contamination, scratches, and chips. Maintain the minimum bend radius of 30 mm for single-mode fibre cable throughout the cable routing — bends tighter than 30 mm cause microbending losses that accumulate along the cable length and reduce the available optical power margin, potentially causing link failures that only manifest at temperature extremes when fibre attenuation increases. When routing fibre cables in industrial environments, use armoured fibre cable rated for the installation environment — crush-resistant armoured cable is recommended for floor-level routing or anywhere the cable may be subject to mechanical stress. After completing the fibre installation, verify the optical power level at each receiver using the QJ71GP21-SX’s self-diagnosis function in GX Works2 to confirm adequate link margin before commissioning the network.
Frequently Asked Questions
Q: What is the difference between the QJ71GP21-SX and the QJ71GP21S-SX, and how do I select the correct module?
A: The QJ71GP21-SX uses single-mode optical fibre supporting station-to-station distances up to 10 km, while the QJ71GP21S-SX uses multimode fibre with a maximum station-to-station distance of 550 m. Both modules implement identical CC-Link IE Controller Network functionality — the selection is based purely on the required cable distance between stations. For most factory and warehouse installations where controllers are within the same building complex (distances under 500 m), the QJ71GP21S-SX multimode variant is the more cost-effective choice. For inter-building or campus-wide installations where cable runs exceed 550 m, the QJ71GP21-SX single-mode variant is required.
Q: Can the QJ71GP21-SX network include stations using both single-mode (QJ71GP21-SX) and multimode (QJ71GP21S-SX) fibre modules?
A: No. Single-mode and multimode fibre modules cannot be mixed on the same CC-Link IE Controller Network ring, as they use incompatible optical wavelengths and connector types. All stations on a single network ring must use either all single-mode (QJ71GP21-SX) or all multimode (QJ71GP21S-SX) modules. If a mixed-distance installation is required, separate sub-networks can be linked via transient communication or via a gateway CPU.
Q: How many link registers (LW) can a single MELSEC-Q CPU station send to other stations on a QJ71GP21-SX network?
A: Each station on a CC-Link IE Controller Network has a configurable send data range within the total LW capacity. The maximum send points per station are configured in GX Works2’s network parameter editor and are allocated from the total network LW capacity of 8,192 points shared across all stations. A typical configuration allocates 256–512 LW send points per station, leaving adequate capacity for all stations to share data simultaneously within the 8,192 total LW limit.
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