Communication link system and its method with protective function

Abstract

The present invention discloses a communication link system having protection function and method, capable of immediately recovering link communication interruption duo to part nodal interface unit damage. It contains increasing series connected first switch between bus and node, each node switching off first switch to continue inner loop back self-checking in communication breakdown, after self-checking passing, closing said first switch to recover communication. To half-duplex bus, it makes inner loop back self-checking through making node inner transmitting device and receiving device simultaneous working. To full duplex bus, it series connects third switch being off-state in normal times between transmitting device and receiving device output end, to realize inner loop back self-checking through closing third switch.

Description

technical field [0001] The present invention relates to communication technology, in particular to the protection technology of communication link. Background technique [0002] At present, in many fields such as industrial control, traffic control, distributed data acquisition system, power system data acquisition and control system, highway toll system, remote control, etc., the RS485 standard is a commonly used electrical characteristic standard, and its main characteristics are as follows: [0003] (1) Balanced differential interface; [0004] (2) Support multipoint-to-multipoint mutual communication; [0005] (3) Tolerate -7V to 12V common mode interference; [0006] (4) Can drive 32 loads; [0007] (5) When the transmission distance does not exceed 50 feet, the maximum rate can reach 10Mbps; [0008] (6) When the transmission rate is 100Kbps, the maximum transmission distance can reach 4000 feet; [0009] (7) Support full-duplex and half-duplex communication (dete...

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Problems solved by technology

[0014] (2) The electrostatic discharge effect can release pulses exceeding 10000V and 60A, and can last for 10ms; while general TTL devices, when encountering 10V pulses exceeding 30ms, will lead to damage

[0017] In practical application, the above scheme has the following problems: when any node interface device on the bus is damaged, the entire communication link will be interrupted

[0018] The main reason for this situation is that due to the long communication distance, high-energy shocks such as lightning strikes and surges may be introduced into the line

Although adding TVS to the node interface circuit of the bus can protect against static electricity and small current surge damage, TVS will still be broken down when subjected to high current and high energy impacts such as lightning strikes and surges

Since the node interface circuits are directly connected to the bus, in many node interface circuits, as long as one TVS is broken down, the bus will be short-circuited to the ground level, resulting in the interruption of the entire communication link.

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