Self-recognition 485 terminal resistance detection circuit based on single-chip microcomputer control

Abstract

The invention discloses a detection circuit for self-identifying 485 terminal resistance based on single-chip microcomputer control, and aims to solve the problems that when terminal matching needs to be carried out in long-distance communication of existing 485 communication equipment, equipment on a bus does not know when the equipment is terminal slave equipment due to the fact that hardware functions and solidification programs of the equipment are consistent when the equipment leaves a factory, and the equipment cannot be matched with the terminal slave equipment when the equipment is the terminal slave equipment. In order to solve the problem that terminal equipment can only be determined by manually pressing a key or dialing a code, which is time-consuming and labor-consuming, the invention determines whether terminal resistor connection is established or not by setting a single chip microcomputer for auxiliary address judgment in each piece of equipment to judge a target address of a message transmitted on a 485 bus. When the address received in the single-chip microcomputer is the same as the 485 address set by the current device, the matching switch of the terminal resistor is turned on, and terminal matching is established for the current slave device and the host, so that self-adaptive identification of the terminal device is realized, the slave device of the device is determined without manually pressing a key or dialing, and convenience and rapidness are achieved.

Description

technical field [0001] The invention belongs to the technical field of terminal communication, in particular to a self-identifying 485 terminal resistance detection circuit controlled by a single-chip microcomputer. Background technique [0002] 485 bus technology is also known as TIA-485-A, ANSI / TIA / EIA-485 or TIA / EIA-485. RS485 is a standard defining the electrical characteristics of drivers and receivers in a balanced digital multipoint system, defined by the Telecommunications Industry Association and the Electronic Industries Alliance. [0003] Digital communication networks using this standard can transmit signals efficiently over long distances and in electronically noisy environments. It is usually used in instrumentation, construction engineering equipment, PLC, and some devices that support 485 communication. [0004] Especially in the field of building control, the scope of 485 bus is more extensive. The 485 bus network topology used in general building control...

AI Technical Summary

Problems solved by technology

[0006] In practical applications, 485 terminal resistors are often forgotten to install due to engineering negligence or other reasons. In the process of equipment development, it is not clear whether the 485 terminal resistor is a master or a slave, and whether it is a terminal device or a non-terminal device. In the case of the situation, it is not appropriate to forcibly install a terminal resistor

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