Mitsubishi AJ71QLP21G GI Fiber Optic Network Module

The Mitsubishi AJ71QLP21G is a specialized GI fiber optic cable network module engineered for the MELSEC-A Series programmable logic controller systems. This module serves as a critical component in establishing high-speed, reliable data communication networks within industrial automation environments. Designed to facilitate robust PLC to PLC networking and remote I/O network configurations, the AJ71QLP21G delivers exceptional performance for distributed control systems requiring stable and interference-resistant data transmission.

Network Architecture and Communication Protocol

The AJ71QLP21G operates as a dual loop fiber optic network module configured for Q mode operation. It utilizes the MELSECNET/10 network protocol, which employs a token ring communication method to manage data transmission between stations. The communication system operates at a speed of 10Mbps, ensuring rapid data exchange across the network. The module supports both PLC to PLC networks and remote I/O networks, making it versatile for various system architectures including management stations and remote control stations.

Technical Specifications and Performance

The AJ71QLP21G provides substantial networking capacity with support for up to 8192 points each for link registers LX, LY, LB, and LW per network. Each station can handle up to 2000 bytes of link data, accommodating complex data exchange requirements. The network supports a maximum of 255 combined PLC to PLC networks and remote I/O networks, with 64 stations connectable per network including one control station and up to 63 normal stations. The module uses NRZI coding for data encoding and HDLC frame format standards for structured data packaging.

For physical connectivity, the AJ71QLP21G utilizes GI optical fiber cable, providing excellent immunity to electromagnetic interference and enabling long-distance communication. The total network distance can extend up to 30 kilometers, with a maximum distance of 2 kilometers between stations. This makes the module particularly suitable for large-scale industrial facilities where control cabinets may be widely distributed across expansive production areas.

Diagnostic and RAS Functions

The AJ71QLP21G incorporates comprehensive RAS functions for system reliability and maintainability. The dual loop design provides automatic loop-back functionality in the event of cable breakage or error detection, ensuring continuous network operation. Built-in diagnostic functions include network monitoring via link special relays and link special registers, enabling operators to perform various diagnostic checks. Transient transmission capabilities support dedicated link instructions for activities such as system monitoring and program upload or download operations. The module also features error detection using CRC, further enhancing data integrity across the network.

Installation and System Integration

The AJ71QLP21G occupies 32 I/O points per slot, requiring assignment as a special 32-point module in the system configuration. This module is compatible with A3VTS multiplex systems and integrates seamlessly into MELSEC-A Series PLC racks. Proper configuration involves setting network parameters, station numbers, and communication modes through the PLC programming environment. The module supports transient transmission for auxiliary data exchange between stations, with dedicated link instruction sets available for customized communication requirements.