CN2657297Y

CN2657297Y - RS 485 bus receiving-transmitting controller

Info

Publication number: CN2657297Y
Application number: CN 200320103637
Authority: CN
Inventors: 方光祥; 唐石平
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2003-10-13
Filing date: 2003-10-13
Publication date: 2004-11-17
Anticipated expiration: 2013-10-13

Abstract

A RS485 bus transceiver controller comprises a receiver and a sender. The two input terminal of the receiver and the two output terminal of the sender are both coupled to a pair of buses respectively. Signals are outputted from the output terminal of the receiver to a communication node. An enable pin of the receiver couples to low level for signal receiving of the receiver. The input terminal of the sender couples to low level. Negative signal sent by the communication node is inputted the enable pin of the sender. The bus couples to high level. Using the RS485 communication transceiver controller of the utility model can keep the various nodes of the RS485 bus communication at receiving state all along, and can also receive bus data at the state of self sending data, thus can check transceiver data, detect bus faults and correct timely, which reduces time of bus collision and enhances the utilization ratio of the bus.

Description

A kind of RS485 bus transceiver controller

Technical field

The utility model relates to communication technical field, relates in particular to a kind of RS485 bus transceiver controller.

Background technology

Along with the development and the increasingly extensive application of computer of digital technology, a present system often is made up of many computers, needs to solve the problem of multistation, telecommunication.Require communication distance be tens meters on during km, extensively adopt the RS-485 transceiver.The RS-485 transceiver adopts balance to send and differential received, therefore has the ability that suppresses common mode disturbances, adds that receiver has high sensitivity, can detect the low voltage that reaches 200mV, so transmission signals can be restored beyond km.Use the RS-485 bus, a pair of twisted-pair feeder just can be realized the multistation networking, constitutes distributed system, and equipment advantage simple, cheap, that can carry out long haul communication makes it obtain using widely.

The RS485 bus communication technology is the technology that comparative maturity is used, because its antijamming capability is strong, communication is reliable, is widely used in the different industries field, as the communication applications between each control subsystem in the system.As: the communication on the automobile between each control assembly; Information interchange in the industrial control system between each control subsystem; Respectively control communication and information exchange or the like between the plate between veneer in the telecommunication apparatus network element.The RS485 bus is as a kind of electrical characteristic standard (seeing EIA/TIARS-485-A) of serial communication, and its characteristics have:

1) balanced differential interface;

2) support intercommunication mutually between multi-multipoint;

3) stand-7V is to the 12V common mode disturbances;

4) can drive 32 loads;

Flank speed can reach 10Mbps (megabyte/second) when 5) transmission range was no more than 50Ft (foot);

Maximum transmission distance can reach 4000Ft when 6) transmission rate was 100Kbps;

7) support full and half duplex communication (by selected device decision);

8) use twisted-pair feeder transmission data, have stronger antijamming capability.

Be illustrated in figure 1 as typical case RS485 bus topolopy figure when adopting half-duplex mode, all communication nodes all link together by shared bus, and R is a receiver among the figure, and G is a transmitter.Tx is an output signal node, and RX is the node received signal, and En is that the transmitting-receiving of bus transceiver enables control signal, and Rt is the build-out resistor of bus, guarantees the signal quality of bus.Each node guarantees only to allow a node to send data on the bus by means such as bus collision detection, data transmission controls, and other node receives data.

When adopting the full duplex mode communication, owing to transceiver bus separates, so can receive and send data simultaneously.And the RS485 bus transceiver controller spare of existing employing half duplex communication, general have 75176 or MAX3485, for each node, adopts control mode as shown in Figure 2, receives and send a pair of differential bus of data sharing.

En is that the transmitting-receiving of bus transceiver controller enables control signal among the figure, from pin two and 3 Enable Pin of input sink R and transmitter G respectively.The signal RX that pin one output is received from bus interface, pin 4 is input to transmitter G with the signal TX that node will send.When the En level was 1, transmitter G was in transmit status, and receiver R is in three-state (being high-impedance state); When the En level was 0, transmitter G was in three-state, and receiver R is in accepting state.Receiver R and the shared differential data bus of transmitter G, Rt is the build-out resistor of bus, purpose is the signal quality that guarantees the differential bus of

6 and 7 outputs.Pin 5 ground connection, pin 8 connects power supply, provides transceiver controller required power supply.

When this node sent data if desired, the En level was 1, and the data on the signal Tx send on the bus, but this moment, the Rx signal is ternary, this node can not receive the data on the bus; En is 0 o'clock, just can receive the data on the bus, but this moment, output enable turn-offed, and this node can not be in the transmission data mode simultaneously.Each node sends data to bus when needed, and node is in accepting state when not sending data.

Existing technical disadvantages clearly for each node that adopts half duplex communication, all can not be accomplished transceive data simultaneously, and promptly this node is in when sending data mode, can not receive the information on the bus.If just there are a plurality of nodes to begin to send data simultaneously on the bus, and they do not receive data, can't carry out bus collision like this detects, cause bus collision (being to have two or more modules will transmit the conflict that conflicting information causes on the bus simultaneously), and can't in time correct.

The utility model content

Technical problem to be solved in the utility model is: each node that overcomes existing RS485 half duplex communication is the deficiency that can't in time correct of the bus collision that brings of transceive data simultaneously, a kind of RS485 bus transceiver controller is provided, make each node energy while transceive data of half duplex communication, detect thereby carry out the RS485 bus failure quickly and easily, in time correct bus collision.

The utility model is to solve the problems of the technologies described above the technical scheme that is adopted to be:

This RS485 bus transceiver controller, comprise receiver and transmitter, described transceiver adopts half duplex communication, transmitter and receiver are connected on the communication bus by a pair of differential lines jointly, the output output signal of described receiver is to communication node, described receiver enable the termination low level, make receiver can carry out the reception of signal; The input termination low level of described transmitter, the Enable Pin of the described transmitter of input after the negate of communication node transmission signal; Described differential lines connects high level.

A described differential lines connects power supply by pull-up resistor, and another root differential lines is connected with build-out resistor by pull down resistor ground connection between two differential lines.

Described communication node sends the Enable Pin that signal input not gate carries out input transmitter after the negate.

The termination low level that enables of described receiver is the direct ground connection of described Enable Pin.

The beneficial effects of the utility model are: utilize the utility model, RS485 communication receiving/transmission controller can guarantee each node of RS485 bus communication, can both be in accepting state all the time, also can receive bus data self sending data mode.Because each node is transceive data simultaneously, the data of also can the node of reception own sending can utilize these characteristics to carry out the verification of transceive data, carrying out bus failure detects, thereby can in time correct, reduce the time of bus collision, improve total line use ratio.

Description of drawings

Typical case RS485 bus topolopy figure when Fig. 1 is half-duplex mode;

Fig. 2 is existing bus transceiver controller structural representation;

Fig. 3 is the utility model bus transceiver controller structural representation.

Embodiment

With embodiment the utility model is described in further detail with reference to the accompanying drawings below:

As shown in Figure 3, for each node on the bus, the Enable Pin RE of the receiver R in the transceiver controller directly pulls down to ground by pin two, guarantees that node can receive the data on the bus all the time, data on the Rx are exported by pin one always like this, give this communication node to handle.

For the transmission of data, to sending data Tx, send into the Enable Pin DE of transmitter G by pin 3 by after the not gate F negate, the data input pin of transmitter G pulls down to low level by pin 4.Two inputs of receiver R and two outputs of transmitter G are connected on a pair of differential lines jointly by

6,7 respectively, wherein a differential lines connects power supply by pull-up resistor R2, another root differential lines is connected with build-out resistor Rt by pull down resistor R1 ground connection between the bus.Pin 5 ground connection, pin 8 connects power supply, provides transceiver controller required power supply.

Like this, when output signal node Tx is 1, after not gate F negate, be 0, transmitter G is ternary, the output high resistant guarantees that by upper and lower resistance R 2, R1 and the build-out resistor Rt of drawing on the bus bus data is 1; When Tx is 0, after not gate F negate, be 1, transmitting terminal G enables, and node sends data 0 on bus, and making bus data is 0.

Like this, each node sends data to bus when needed, and each node all is in the bus data state that receives always.The utility model can guarantee to adopt each node of RS485 half duplex communication, and no matter whether this node sends data to bus, can both normally receive the data on the bus.

By this improvement, guaranteed that node can be in data receiving state all the time, also can receive the data that this node sends.When a plurality of nodes send data simultaneously and cause bus collision, each node that sends data can receive bus data simultaneously, the data that receive are carried out verification can detect bus collision, can carry out to more convenient and quicker bus failure detects, thereby can in time correct, reduce the shared time of bus collision, improved the utilization ratio of bus.

Claims

1, a kind of RS485 bus transceiver controller, comprise receiver and transmitter, described transceiver adopts half duplex communication, transmitter and receiver are connected on the communication bus by a pair of differential lines jointly, the output output signal of described receiver is to communication node, it is characterized in that: described receiver enable the termination low level, make receiver can carry out the reception of signal; The input termination low level of described transmitter, the Enable Pin of the described transmitter of input after the negate of communication node transmission signal; Described differential lines connects high level.

2, RS485 bus transceiver controller according to claim 1 is characterized in that: a described differential lines connects power supply by pull-up resistor, and another root differential lines is connected with build-out resistor by pull down resistor ground connection between two differential lines.

3, RS485 bus transceiver controller according to claim 1 and 2 is characterized in that: described communication node sends the Enable Pin that signal input not gate carries out input transmitter after the negate.

4, RS485 bus transceiver controller according to claim 1 is characterized in that: the termination low level that enables of described receiver is the direct ground connection of described Enable Pin.