CN2187857Y - Two-wire system serial curent ring communication bus - Google Patents

Abstract

The utility model relates to two-wire system serial electric current loop communication bus which is a single electric current loop communication line formed by that one or a plurality of direct current voltage sources and a plurality of coupling mechanisms are distributively concatenated with an existing two-wire system communication line (formed by two pieces of conducting wire), wherein, the coupling mechanisms are integrated twice by existing optical couplers, transistors, and integration blocks and encapsulated by standard O-shaped 25-pin plugs and the molded casings. The o-shaped 25-pin plug of each coupling mechanism is connected with the serial port of equipment such as a computer, etc., or an analog signal interface of an existing modem circuit. The molded casing coil-out hole of each coupling mechanism is provided with two pieces of leading wire which are connected in series with the communication line, and optical coupling electric insulated isolation is arranged in the coupling mechanisms between the equipment and the communication line.

Description

Two-wire system serial curent ring communication bus

The utility model relates to a kind of asynchronous serial cable data communication interface mode.

At present, known asynchronous serial cable data communication form always has two classes, i.e. baseband digital signal transmission and adopt the analog signal transmission two class forms of modulatedemodulate device circuit below is discussed respectively.

The first kind: base band asynchronous serial cabled digital signal transmission form

At present, the known standard asynchronous serial communication interface mode that belongs to this type of baseband digital signal transmission form has three kinds now, and they are:

1、RS232C（RS232A、RS232B）。

2, RS422, RS423 and RS449.

3,20mA electric current loop.

Preceding two kinds or one of them (first kind at most) have almost all been adopted on the existing all-purpose computer, the third does not all adopt in conventional computer, just in some special digital instrumentations, use, below existing once these the three kinds of interface modes pluses and minuses technically of division.

First kind: RS232C(RS232A, RS232B) the asynchronous serial communication interface mode

Connect in the mode at this, the RS232A modified model is RS232B, and the modified model of RS232B is RS232C, preceding two existing potassium hydroxides, and now that commonly used almost is RS232C entirely.

The RS232C standard code has 25 lines, the D shape 25 core socket plug connectors of adopting international standards, use 21 signal line, in general direct communication, only use several signal line, most of idle, mainly contain and send data wire TXD(output signal) the 2nd pin, receive data wire RXD(input signal) the 3rd pin and these three lines of common signal ground wire the 7th pin CWD.That is to say that adopting that existing RS232C asynchronous serial communication interface mode is minimum will be with three connection; On the other hand, the logic level of RS232C regulation numeral " 1 " is-3V～-15V, the logic level of digital " 0 " is+3V～+ 15V, belong to the voltage interface mode, data transmission bauds is 50～9600 bauds, and cable length (communication distance) is limited in 50 feet.

Second kind: RS422, RS423 and RS449 asynchronous serial communication interface mode

This interface mode is then to recommend the international standard announced for the deficiency that remedies RS232C, also belongs to the voltage interface mode, at least will be with three above connections, owing to taked measure such as balance transmission, communication distance is far away than RS232C.

The third: 20mA electric current loop interface mode

This kind mode and preceding two kinds have a very big difference, it is as logical one the 20mA electric current, zero current as logical zero, just represent the data bit signal that transmits with having or not of current signal, belong to the electric current loop interface mode, the computer that has, teleprinters etc. just are furnished with this mode, but existing this electric current loop interface mode has a significantly deficiency, could constitute both sides' communication condition by two current loops exactly, each current loop can only adopt single worker's communication modes, that is to say and to constitute two current loops with 4 connections, and the driving power power of these two current loops respectively by two equipment of mutual communication+the 5V power supply provides, have directly between communication line and the equipment to be electrically connected, certainly will just reduce the fail safe and the reliability of device talk work like this.But generally speaking, because existing 20mA electric current loop interface mode adopts existing optocoupler to make between two current loops and has realized the electric insulation isolation, this compares with preceding two kinds of voltage interface modes bigger improvement aspect the anti-interference, therefore existing 20mA current interface mode is much far away than RS232C mode communication distance, adopts the following communication speed of 9600 bauds can be at two kilometers with interior work.Communication distance also can be more farther when speed was low.

More than be three kinds of known standard asynchronous serial communication interface modes, in addition, the non-standard serial voltage interface mode that also has a kind of TTL of employing or CNOS level, its working power voltage is+5V, communication distance is very short, be commonly used in circuit in the instrument and equipment, the communication number of lines also is three lines, and promptly one sends line TXD, a reception line RXD and a common signal ground wire GND.

Second class: the analog signal transmission form that adopts modem circuit

The first kind baseband digital signal transmission form of discussing above, adopt voltage system or employing current system no matter be, all be between 1 state and 0 state, to have a series of square waves and the rectangular pulse of obvious sudden change to exist on the line during data, therefore this transmission means just can only be used under communication line and low speed transmissions situation at short square, especially unfavorable to long Distance Transmission, because long Distance Transmission can make this digital square wave produce very severe distortion, cause communication to make mistakes, influencing communication normally carries out, just because of this reason, so usually do not adopt first kind form for the long-range data communication more than tens kilometers, but employing modulation-demodulation technique, transmitting on the communication line with the analog signal after the digital square-wave frequency modulation, because there is not the sort of sudden change in the digital square-wave in analog signal in transmission course, analog signal is the signal that a kind of current/voltage changes the frequency band relative narrower continuously, in transmission course, be difficult for distorting, promptly be that some variation is also corrected by circuit such as filters easily, so stronger anti-interference is arranged, just because of above-mentioned reason, so at present all long-distance data communications, nearly all adopt modulation demodulation system.

At present, known when on the two-wire system communication line, adopting modulator-demodulator to carry out remote data communication, nearly all be to adopt the electromagnetic coupled coil (or being called coupling transformer) of balanced type to come the coupled simulation signal between modulator-demodulator and the communication line, and coupling coil is connected in parallel on the communication line, as shown in Figure 5, in Fig. 5,10 is the electromagnetic coupled coil, 11 is modulator-demodulator, and 3 is the two-wire system communication line.Communication line has been not a current circuit just like this, but a plurality of current circuits, on the line and the coupler that connects multiloop is just many more more, shunting to signal is also just many more, lengthening along with communication distance, also just big more to the decay of signal, even will establish the decay of repeating equipment replacement, this decay is more much bigger than the decay that the distributed inductance of circuit and distributed capacitance distributed resistance etc. cause.On the other hand, with this and connect the mode transmission signals, what each coupling coil sent output and reception input all is voltage signal, so resist dried dominance that the degree of balance and the impedance matching of communication line are just required the comparison height in order to improve, the communication line of this transmission voltage signal, electromagnetic interference to external world often all are highstrung, all require away from interference sources such as power circuits when therefore this communication line sets up, having a bit, is exactly that the cored often volume of coupling coil is bigger again.

In sum, three kinds of standard communication interface mode (RS232C of present known first kind base band asynchronous serial cabled digital signal transmission form, RS422, RS423 and RS449, the 20mA electric current loop) and a kind of non-standard communication interface mode (adopt TTL, the voltage interface of CNOS level) three common shortcomings is all arranged, it is: they can only carry out (1) direct loic and connect the data communication that realizes between the two between two equipment, and can not be with three, four, five and even more s' equipment direct loic links together, for they provide a shared data communication bus, realize the mutual communication of bus mode, want to realize the mutual communication between the multiple devices, just can only finish by manual switching with the hardware of mechanical switch and so on; (2) number of lines of their used communication lines is all more than three or three; (3) their used communication lines all have directly with communication apparatus both sides or at least one side and are electrically connected, and have therefore also just reduced fail safe, anti-interference and the functional reliability of device talk.

Adopt the asynchronous serial cable data communication form of modem circuit transmission of analogue signal at present known second class, use on two-wire system in special use long-range (in tens to the 100 kilometers) communication line, have following three important disadvantages when especially on the distributed communication line of the more line style of distributed points, using.(1) coupling coil and circuit parallel operation, cause signal in transmission course, to decay much with the lengthening of distance, the signal that send any point on the circuit may not maintain more approaching signal strength signal intensity on other any one acceptance point on the line, even it is much poor, so that cause communication to make mistakes (referring under the situation of not establishing repeating): (2) adopt the solenoid coupler, cause coupling and body long-pending very big; (3) coupling coil and communication line and connect adopt the voltage system transmission of analogue signal, and circuit interference voltage to external world is very sensitive, and anti-interference is poor, require very high to the impedance matching and the degree of balance of line facility.

In above explanation, with reference to following several documents to immediate prior art.

(1) work such as " practical application of microcomputer data communication and test " ［ U.S. ］ ELJZABETH A.NICHOLS, Xu Bo etc. translate.Beijing Ke Hai training center of the Chinese Academy of Sciences, in November, 1986 version.

(2) " microcomputer interface ", ［ U.S. ］ HAROLOS.STONE work, Sun Zhenyun etc. translate, publishing house of Tsing-Hua University, in September, 1985 front page.

3, " IBN PC/XT(Great Wall 0520) interfacing and application thereof " Wang Shiyuan, Wu Zhifang writes publishing house of Nankai University front page in April nineteen ninety.

4, " IBN PC series microcomputer interface and Principle of Communication and example ", Li Kechun chief editor, Dalian Institute of Technology publishing house front page in June nineteen ninety.

5, " data transmission technology basis " ［ day electrical communication association compiles, Cai Daofa translates, People's Telecon Publishing House, November in 1984 the 1st edition.

The purpose of this utility model provides a kind of two-wire system serial electric current loop communication bus interface mode, and necessary key technology parts--two-wire system serial electric current loop communication bus optical coupling serial line interface communication coupler is hereinafter to be referred as communication coupler or coupler.It has overcome several shortcomings of known existing asynchronous serial communication interface mode in the existing above-mentioned two class data communication forms, only use the single electric current loop communication line of the two-wire system that constitutes by two leads just can realize half-duplex bus formula communication between Liang Tai, three, four, five and even more the serial communication equipment, and between individual device and communication line, realized the isolation of optical coupling electric insulation.

The purpose of this utility model is achieved in that one or more direct voltage sources and several is adopted existing optocoupler, transistor and integrated package are through the integrated communication coupler of making of secondary, distribution is connected in the existing two-wire system communication line that is made of two leads, constitute a single electric current loop communication line, the communication coupler adopts standard D shape 25 core plugs and moulds the shell solid encapsulation, its D shape plug links to each other with the serial port of equipment such as computer or the analog signal interface of existing modem circuit, it is moulded the shell wire hole and draws two output lines of both positive and negative polarity and be connected in series with communication line, is that the optical coupling electric insulation is isolated in coupler inside between equipment and the circuit.A communication line like this is the two-wire system serial electric current loop communication bus of equipment such as these computers.In the line direct voltage source of polyphone is the bus current drive source, and for communication bus provides the line work electric current, voltage is just got exhausted length and what of coupled in series device in communication line, and the line work quiescent current is made as 10mA～20mA and gets final product.Circuit adopts the half duplex communication mode, and the reception operating voltage of every coupler is reduced to 1.5～1.8 volts.

Owing to adopted such scheme, therefore just can constitute a single electric current loop communication line with the existing two-wire system communication line that two leads constitute, realize that many computer single-chip microcomputers etc. have the asynchronous half-duplex bus type data communication of serial interface devices, and realized that between individual device and communication line the optical coupling electric insulation isolates.Compare with existing several interface modes of existing two class cable data communication forms, stronger than the anti-interference of 20mA electric current loop interface mode more excellent in existing several baseband transmission interface modes, communication distance is farther, and performance is more excellent; The communication coupler made from such scheme, be used to adopt the data communication interface mode of modem circuit transmission of analogue signal, than the little dozens to one hundred times of existing solenoid coupler volume, owing to adopt the current signal transmission in the line, anti-interference is also much better than than the existing solenoid coupler of voltage signal transmission that adopts on the line.Because this coupler is to be connected in the communication line to work, therefore and have and being connected in electromagnetic coupler on the communication line compares and has reduced coupler and connected the shunting that the line signal electric current is caused, can make the signal code intensity on the whole communication line, except that the decay that circuit distributed inductance distributed capacitance and distributed resistance cause, keep in balance substantially, help signal long-distance transmissions and reception, can on 50～100 kilometers circuit, not establish repeating equipment and the reliable transmitting data signal, remove to building the disposable investment of sound station equipment reaching long-term maintenance cost and trouble later on from, less demanding to the degree of balance and the impedance matching of communication line equipment.

Below in conjunction with drawings and Examples the utility model is further specified.

Fig. 1 is an application general illustration of the present utility model.

Fig. 2 is the shape assumption diagram of the coupler that provides of the utility model.

Fig. 3 is the electrical schematic diagram of first embodiment of the coupler that provides of the utility model.

Fig. 4 is the electrical schematic diagram of second, third two embodiment of the coupler that provides of the utility model.

Fig. 5 is the application general illustration that known existing employing modem circuit carries out the analog signal transmission data communication.

Bus driver is called for short in 1. two-wire system serial electric current loop communication bus circuit driving DC voltage sources among the figure.Fig. 1 is that a both-end drives the bus schematic diagram, and when only adopting the single-ended drive bus with a bus driver, bus does not have an end of driver and answers the short circuit closure.2. the communication coupler that provides of the utility model or claim coupler.3. two-wire system communication line.4.D shape 25 core international standard connector plugs.5. mould shell with the supporting standard of plug 4.6. the garden shape two core coaxial sockets that link to each other with 5 are used for moulding shell 5 from plug and draw two both positive and negative polarity lead-out wires of contacting mutually with communication line, and its inner core is that positive periphery is for negative.8. from coupler, draw the electrode line of contacting mutually with communication line.9. from coupler, draw the negative line of contacting mutually with communication line.Among Fig. 3 12,13,14,15 and 16 lines are respectively the line of the 7th, 2,3,4 and 20 pins of receiving the RS232C standard interface.Remainder among the figure is illustrated below in conjunction with each embodiment.

The communication coupler that the utility model provides has three embodiment, and first embodiment is used for the first kind baseband transmission data communication method of this specification beginning narration, and what receive and send is digital square wave rectangular pulse, and coupler works on off state.The design alternative of this embodiment present most widely used the most general RS232C general international standard serial line interface be design considerations, therefore the coupler made from this embodiment adopts the encapsulation of general international standard 25 core D shape cellular type plugs, can directly link to each other with the standard 25 core D shape pin type sockets of the equipment such as computer with standard RS232C serial communication interface.

As previously mentioned, the RS232C serial line interface is a kind of voltage interface, logic " O "+3V～+ 155V between, logical one-3V～-15V between, and in the described communication current loop of the utility model bus, in the baseband transmission mode, logical signal is to represent with the current signal in the communication line.Therefore, carry out interface to this electric current logical signal with RS232C voltage logical signal is connected, the communication coupler that the utility model provides just must have by RS232C voltage logical signal to the translation function of communication line electric current logical signal with by the electric current logical signal of the communication line translation function to RS232C voltage logical signal, that is to say that this coupler should be able to finish by voltage signal to current signal and by the bi-directional conversion of current signal to voltage signal.In first coupler embodiment shown in Figure 3, by the RS232C voltage signal is that to adopt model be that the transmission photoelectrical coupler 35(of 4N35 is called for short optocoupler when line current signal is changed) and Darlington 37 realize, 40 is the transistor base biasing resistor, resistance is 10K～22K, and resistance is neglected the transistor multiplication factor greatly and decided.48 is the reverse protection diode of coupler output.By the current signal of communication line in the conversion of RS232C voltage signal, for obtain the RS232C interface required-3V～-15V to+3～+ the 15V logic level, just need a positive voltage and a negative supply voltage, indispensable, in order no longer additionally to increase a positive-negative power, the utility model has adopted takes from the design philosophy that the RS232C interface is used for the RS232C interface, owing to adopt half-duplex operation during this coupler communication, what the 2nd of RS232C the transmission pin was just in time exported when receiving is one-12V voltage and constant, therefore just can with this-12V required negative supply of generation RS232C signal during as a reception, be electrically connected as shown in Figure 3, yet a positive supply to be arranged also, where this positive supply from getting? the designer confirms to find, the 4th and the 20 two output pin of RS232C interface be total output-12V under normal conditions, and have at least one of them to be, therefore under the condition of not using the communication of serial port interconnection, fully can be when using the RS232C interface with these two pins as providing low power power line to use, from this point, the designer uses rectifier bridge 33 and the 17555 type CNOS time-base integrated circuits 34 and 42 among Fig. 3,43,44,45,46, the square-wave oscillator that 47 relevant original papers constitute, with the 4th in standard RS232C interface and the output of the 20 two pin-the 12V voltage transformation obtained a positive supply, thereby solved required positive supply problem, the positive supply that adopts this method to obtain, by moving on the 3K resistance 41 among Fig. 3 on the output collector electrode that receives photoelectrical coupler 36, can on collector terminal 14, obtain during reception-6V～+ the voltage logic level of 6V, meet the reception needs that RS232C the 3rd receives pin fully, this method that present embodiment adopts, avoided usually adopting for linking to each other with standard RS232C interface ± 12 power supplys and level shifting circuits such as NC1488 and NC1489, simple in structure.

In Fig. 3, transmission photoelectrical coupler 35 and diode 38 oppositely end during data transmission line 13 output low levels, on the contrary conducting.From the current signal that circuit receives, the RS232C voltage signal that process reception photoelectrical coupler 36 and its output collector electrode pull-up resistor 41 translation circuits such as grade obtain is sent to the 3rd pin of RS232C interface by Data Receiving line 14; 39 for sending the input current-limiting resistance of photoelectrical coupler 35, and resistance is 510 Ω～620 Ω.12 lines connect the 7th pin common signal ground of RS232C interface, and 9 and 8 two lead-in wires are the negative anodal line of coupler exit.

Second embodiment of the communication coupler that the utility model provides, second class that is used for this specification beginning narration adopts the data communication method of modem circuit transmission of analogue signal, what receive and send is the continually varying analog signal, as sine wave etc., coupler works in two-way magnifying state, adopt the half duplex communication mode, be electrically connected principle, in the circuit in the frame of broken lines is not included in Fig. 4.Specifically, transmitting-receiving conversion and control line 20 connects the 10th pin output high level of D shape 25 core plugs during reception, transistor 23 is saturated, electric current by transmission photoelectrical coupler input is bigger, cause its output triode saturated, thereby stoped the analog signal transmission that sends data wire 21 outputs to output, and then also make transistor 28 saturated, electric current in the communication line is just by receiving the input of optocoupler 31 at this moment, be connected into an emitter follower owing to receive the output of optocoupler, so its emitter is with regard to the exportable analog signal that receives, receive the 3rd pin of D shape 25 core plugs by 18 lead-in wires, lead-in wire 17 transmission circuits of taking over to linking to each other with D shape plug from 9 pin of D shape 25 core plugs provide+the 5V power supply.Data analog signal sends the 2nd pin that line 21 is received D shape 25 core plugs.Transmitting-receiving control line 20 is a low level during transmission; triode 23 ends; the current ratio of the input by sending photoelectrical coupler 30 receives into little; send optocoupler 30 output triodes and be in magnifying state; and then make triode 28 also be in magnifying state; the digital analogue signal that is sent by the lead-in wire 21 that sends optocoupler 30 input sides just can be coupled to its output by optocoupler 30 like this; become the current signal on the communication line; lead-in wire 19 connects the 7th pin of D shape 25 core Pin contacts; coupler output diode 32 is used for reverse protection, reverse breakdown when preventing coupler work.Lead-in wire 8 and 9 two both positive and negative polarity lines of drawing for coupler Plastic Package shell wire hole; be serially connected in the communication line during use; in order to prevent that the coupler forward breakdown from damaging (allowing ceiling voltage is 80 volts), circuit one sides that should go between two of coupler output are also carried an external piezo-resistance of 50～60V or other conventional over-voltage over-current protection circuit during use.

The 3rd embodiment of the communication coupler that the utility model provides, second class that also is used for this specification beginning narration adopts the data communication method of modem circuit transmission of analogue signal, this embodiment implements on the basis of second embodiment circuit, concrete grammar is: between the D shape Pin contact 4 of second embodiment coupler inside and coupled circuit, add modulation integrated package and external crystal thereof such as adopting existing NC145443 model, the modulation-demodulation circuit that components and parts such as small capacitor and resistance constitute, the electric principle of the 3rd embodiment of communication coupler be comprise in Fig. 4 frame of broken lines shown in whole circuit of Fig. 4 of circuit, D shape Pin contact is the data transmission line TXD with this modulation-demodulation circuit in coupler inside, Data Receiving line RXD, signal ground GND, the power supply vdd line, reiving/transmitting state control line NDD etc. link to each other, the analog signal output line of this modulation-demodulation circuit and incoming line link to each other with the described respective signal line of former second embodiment, D shape Pin contact links to each other with the non-standard serial port with TTL and CONS level during use, this interface provides whole power for the inner circuit that joins with D shape plug that is coupled, resistance 50 is 1K among Fig. 4,49 for frequency of oscillation be the crystal of 3.579NHz.NC145443 is the communication integrated package that U.S. Notorola company produces, and all electric capacity is the nonpolarity superminiature capacitor of 0.1uf.All the other requirements of the 3rd embodiment are identical with second embodiment.

For standardization and normalization, three embodiment of the communication coupler that the utility model provides all adopt identical appearance structure shown in Figure 2, its circuit part all adopts the integrated solid encapsulation of secondary integrated technique at plug shown in Figure 24 and mould in the shell 5, uses as a solid members.In order to distinguish with easy to use, D shape 25 core plugs of first embodiment adopt the cellular type plug, second and third, two embodiment all adopt Pin contact.All should note the connection polarity of two output leads when these three kinds of couplers use, two positive and negative lead wires of output connect and can not cause coupler to damage inverse time, only can make communication failures.

The communication bus driver that the utility model is described is the adjustable or fixed voltage source of direct current that adopts existing known technology to make.

Claims (2)

1, a kind of two-wire system serial electric current loop communication bus, the two-wire system communication line that constitutes by two leads, one or more direct voltage sources and communication coupler are formed, direct voltage source provides power for communication line, equipment such as computer single-chip microcomputer are with its RS232C standard serial interface, or employing TTL, the non-standard serial line interface of CMOS level voltage, or the analog signal interface of modem circuit is connected with the standard D shape plug of communication coupler, by realizing the data-signal coupling between communication coupler and the communication line, it is characterized in that: direct voltage source and communication coupler are to distribute to be connected in the communication line, and whole communication bus circuit is that an electric current folk prescription is to the single electric current loop communication line of the single-current system that flows.

2, communication bus according to claim 1, it is characterized in that: the communication coupler is general D shape 25 core plugs and mould shell encapsulation of adopting international standards, its inside is divided into two parts, a part is connected with O shape 25 core plugs, another part, by one or two core circular coaxial cable socket, drawing two lead-in wires of both positive and negative polarity of contacting mutually with the communication bus circuit from the circular wire hole of plastic packaging shell, is that the optical coupling electric insulation is isolated between two parts.

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