CN206894653U - Software switching circuit based on RS232 and RS485 - Google Patents

Abstract

The utility model discloses a kind of software switching circuit based on RS232 and RS485,Including power communications circuit,Power ＆ environment supervision circuit and communication switching circuit,Power communications circuit is connected with power ＆ environment supervision circuit and communication switching circuit respectively,Communication switching circuit includes the 43rd photoelectric isolated chip,49th optocoupler,55th optocoupler,58th multiplexer,RS485 transceiving chips and RS232 transceiving chips,7th pin of the 43rd photoelectric isolated chip is connected with the 4th pin of the 58th multiplexer,6th pin of the 43rd photoelectric isolated chip is connected with the 4th pin of RS485 transceiving chips and the 11st pin of RS232 transceiving chips respectively,4th pin of the 49th optocoupler is connected with the second pin of RS485 transceiving chips and the 3rd pin respectively.It is more convenient that the utility model can reduce hardware cost and cost of labor, switching.

Description

Software switching circuit based on RS232 and RS485

Technical field

It the utility model is related to interface switching field, more particularly to a kind of software exchange electricity based on RS232 and RS485 Road.

Background technology

In the communications portion of industrial control product, even if CAN communication, for RS232 and RS485, CAN has transmission Advantage in terms of stable and transmission speed, but it is in the majority still with RS232 and RS48 serial communication modes for industry control part. In communications equipment room, because calculator room equipment is more, such as Switching Power Supply, access controller, the equipment such as location server and air-conditioning, but It is that these equipment may use RS232 communications to be communicated using RS485, but due to the power ＆ environment supervision system of computer room In general serial ports is limited for the control chip of use, can not only accomplish RS232 equipment and RS485 equipment, therefore same string Mouth is if necessary to compatible RS232 and RS485, it is necessary to which serial ports part is switched over.Switching can be divided into software exchange and hard Part switches two kinds.Wherein hardware exchange mainly using toggle switch either jump cap switch over, but this mode due to Need to carry out to take power ＆ environment supervision system apart and switch over, therefore cause the inconvenience of installation, add hardware cost And cost of labor.

Utility model content

The technical problems to be solved in the utility model is, for the drawbacks described above of prior art, there is provided one kind can reduce The software switching circuit of hardware cost and cost of labor, switching more easily based on RS232 and RS485.

Technical scheme is used by the utility model solves its technical problem：Construct a kind of based on RS232's and RS485 Software switching circuit, including power communications circuit, power ＆ environment supervision circuit and communication switching circuit, the power communications circuit difference It is connected with the power ＆ environment supervision circuit and communication switching circuit, the communication switching circuit includes the 43rd Phototube Coupling core Piece, the 49th optocoupler, the 55th optocoupler, the 58th multiplexer, RS485 transceiving chips and RS232 transceiving chips, 7th pin of the 43rd photoelectric isolated chip is connected with the 4th pin of the 58th multiplexer, described 6th pin of the 43rd photoelectric isolated chip receives and dispatches core with the 4th pin and RS232 of the RS485 transceiving chips respectively The 11st pin connection of piece, the 4th pin of the 49th optocoupler draw with the second of the RS485 transceiving chips respectively Pin and the connection of the 3rd pin, the 4th pin of the 55th optocoupler and the 6th pin of the 58th multiplexer Connection, the first pin of the 58th multiplexer are connected with the 12nd pin of the RS232 transceiving chips.

Described in the utility model based in RS232 and RS485 software switching circuit, the communication switching circuit is also Including the 20th paster magnetic bead, the 22nd paster magnetic bead, the 24th paster magnetic bead, the 26th paster magnetic bead, the 50th Nine Transient Suppression Diodes, the 61st Transient Suppression Diode, the 64th Transient Suppression Diode, the suppression of the 73rd transient state Diode processed, the 75th Transient Suppression Diode, the 78th Transient Suppression Diode, the 23rd fuse, the 20th Six fuses, the 29th fuse, the 32nd fuse, the 35th fuse, the 66th discharge tube, the 67th Discharge tube, the 71st discharge tube, the 72nd discharge tube, the 81st discharge tube, the 82nd discharge tube and connector, institute The one end for stating the 20th paster magnetic bead is connected with the 6th pin of the RS485 transceiving chips, the 20th paster magnetic bead Other end one end with the 59th Transient Suppression Diode, one end of the 23rd fuse and the 60th a flash respectively One end connection of state diode, one end of the 22nd paster magnetic bead connects with the 7th pin of the RS485 transceiving chips Connect, the other end of the 22nd paster magnetic bead other end with the 61st transient diode, the 26th respectively One end of fuse connects with one end of the 64th transient diode, one end of the 24th paster magnetic bead with it is described The 14th pin connection of RS232 transceiving chips, the other end of the 24th paster magnetic bead is respectively with the described 73rd One end of transient diode, one end of the 29th fuse connect with one end of the 75th transient diode, and described second One end of 16 paster magnetic beads is connected with the 13rd pin of the RS232 transceiving chips, the 26th paster magnetic bead One end and the 32nd of the other end other end with the 75th transient diode, the 78th transient diode respectively One end connection of fuse, the other end of the 23rd fuse is respectively with one end of the 66th discharge tube and connecing The 4th pin connection of plug-in unit, the other end of the 26th fuse respectively with one end of the 67th discharge tube and The 5th pin connection of connector, the other end of the 66th discharge tube, the other end of the 67th discharge tube, the 70th One end of one discharge tube and one end of the 72nd discharge tube are grounded, the other end of the 29th fuse respectively with institute The other end for stating the 72nd discharge tube connects with the second pin of connector, the other end difference of the 32nd fuse It is connected with the other end of the 71st discharge tube and the first pin of connector, one end point of the 35th fuse Be not connected with one end of the 81st discharge tube and one end of the 82nd discharge tube, the 81st discharge tube it is another The other end of one end and the 82nd discharge tube is grounded.

Described in the utility model based in RS232 and RS485 software switching circuit, the power ＆ environment supervision circuit bag Include microcontroller, reset chip, flash chip and crystal oscillator, the 54th pin and the flash chip of the microcontroller The 6th pin connection, the 55th pin of the microcontroller is connected with the 5th pin of the flash chip, described micro- 60th pin of controller is connected with the first pin of the reset chip, the 5th pin and the crystalline substance of the microcontroller One end connection shaken, the 6th pin of the microcontroller are connected with the other end of the crystal oscillator.

Described in the utility model based in RS232 and RS485 software switching circuit, the power communications circuit bag Include the switch chip being sequentially connected, isolating transformer, rectifier bridge, the first filter circuit, mu balanced circuit, linear regulator chip and Two filter circuits.

Implement the software switching circuit of the present utility model based on RS232 and RS485, have the advantages that：Communication Power supply circuit, power ＆ environment supervision circuit and communication switching circuit, communication switching circuit include the 43rd photoelectric isolated chip, the 4th 19 optocouplers, the 55th optocoupler, the 58th multiplexer, RS485 transceiving chips and RS232 transceiving chips, RS485 are received Send out chip and RS232 transceiving chips share a reception pin, that is, the 6th pin of the 43rd photoelectric isolated chip, hair Send pin access the 43rd photoelectric isolated chip the 4th pin carry out software exchange control, so can reduce hardware cost and Cost of labor, switching are more convenient.

Brief description of the drawings

, below will be to embodiment in order to illustrate more clearly of the utility model embodiment or technical scheme of the prior art Or the required accompanying drawing used is briefly described in description of the prior art, it should be apparent that, drawings in the following description are only It is some embodiments of the utility model, for those of ordinary skill in the art, before creative labor is not paid Put, other accompanying drawings can also be obtained according to these accompanying drawings.

Fig. 1 is the structural representation in the software switching circuit one embodiment of the utility model based on RS232 and RS485 Figure；

Fig. 2 is the circuit theory diagrams of communication switching circuit in the embodiment；

Fig. 3 is the circuit theory diagrams of power ＆ environment supervision circuit in the embodiment；

Fig. 4 is the circuit theory diagrams of power communications circuit in the embodiment；

Fig. 5 is the structural representation of the 58th multiplexer in the embodiment.

Embodiment

Below in conjunction with the accompanying drawing in the utility model embodiment, the technical scheme in the embodiment of the utility model is carried out Clearly and completely describing, it is clear that described embodiment is only the utility model part of the embodiment, rather than whole Embodiment.Based on the embodiment in the utility model, those of ordinary skill in the art are not under the premise of creative work is made The every other embodiment obtained, belong to the scope of the utility model protection.

In the utility model based in RS232 and RS485 software switching circuit embodiment, RS232 and RS485 should be based on Software switching circuit structural representation it is as shown in Figure 1., should the software switching circuit bag based on RS232 and RS485 in Fig. 1 Include power communications circuit 1, power ＆ environment supervision circuit 2 and communication switching circuit 3, power communications circuit 1 respectively with power ＆ environment supervision circuit 2 Connected with communication switching circuit 3.Power communications circuit 1 is used to provide work electricity for power ＆ environment supervision circuit 2 and communication switching circuit 3 Source.

Fig. 2 is the circuit theory diagrams of communication switching circuit in the present embodiment, and the communication switching circuit 3 includes the 43rd light It is electrically isolated chip U43, the 49th optocoupler U49, the 55th optocoupler U55, the 58th multiplexer U58, RS485 transmitting-receivings Chip U45 and RS232 transceiving chip U53, the 43rd photoelectric isolated chip U43 the 7th pin and the 58th multiplexing Device U58 the 4th pin connection, the 43rd photoelectric isolated chip U43 the 6th pin respectively with RS485 transceiving chips the Four pins are connected with the 11st pin of RS232 transceiving chips, and the 49th optocoupler U49 the 4th pin is received with RS485 respectively Hair chip U45 second pin connects with the 3rd pin, the 55th optocoupler U55 the 4th pin and the 58th multiplexing Device U58 the 6th pin connection, the 58th multiplexer U58 the first pin and the 12nd of RS232 transceiving chips U53 the Pin connects.

UART2_RXD, UART2_TXD and GND (reference can be made to Fig. 4) are serial ports Transistor-Transistor Logic levels.UART2_CTL receives for RS485 Chip U45 transmitting-receiving control pin is sent out, UART2_SEL is RS232/RS485 base pin selections, makes power ＆ environment supervision circuit by control 2 and PERCOM peripheral communication part carry out signal isolation.RS232 typical case is the communication between system, therefore between each system Isolation design has become very necessary.Communication isolating can not only be endangered with protection device from the high pressure in bus, can be with The ground connection backflow in bus is eliminated, while isolation can also effectively reduce the error code and mistake of inter-system data transmission.Therefore Isolated in circuit using the 43rd photoelectric isolated chip U43, the 49th optocoupler U49, the 55th optocoupler U55.

Wherein, the 43rd photoelectric isolated chip U43 uses ADUM1201, and its advantage is：1st, the higher flank speed of speed 125Mbps can be reached；2nd, power consumption more low-power consumption is less than with 1/10 of Traditional photovoltaic isolator during data transmission rate, and minimum works Electric current 0.8mA；3rd, the higher time sequence precision of performance, transient state common mode inhibition power, interchannel matching degree are superior to Traditional photovoltaic isolation Device；4th, the smaller integrated level of volume is higher, and printed circuit board (PCB) area is the 40% of Traditional photovoltaic isolator.

There are respective power supply and reference ground, supply voltage scope in the both ends that 43rd photoelectric isolated chip U43 is isolated Between 2.7V to 5.5V, low voltage power supply can be so realized, so as to further reduce system power dissipation.Power supply and reference ground it Between need to access 10 μ F to 0.1 μ F electric capacity, to filter out High-frequency Interference, the distance between electric capacity and power supply should within 20mm, More preferable filter effect can so be reached.Due to two channel isolation matcheds, interchannel crosstalk very little, and use two Passage input and output reverse design, the characteristic of RS232/RS485 bus bidirectional transmit-receives is especially suitable for, greatly simplifies isolator and institute Isolate the hardware connection at both ends.It should be noted that GND is a different reference ground from GRS4, the effect of isolation otherwise will not reached Fruit.

In the partial circuit, RS485 transceiving chips U45 turns 485 transceiving chips using SN65HVD3082 as TTL, RS232 transceiving chips U53 uses SIPEX SP3232EEN.RS485 transceiving chips U45 and RS232 transceiving chips U53 shares one Individual reception pin, that is, the 43rd photoelectric isolated chip U43 the 6th pin.The 58th multichannel of pin access is sent to answer Software exchange control is carried out with device U58 the 4th pin, the 58th multiplexer U58 is using TI's (Texas Instrument) 74LVC1G3157, the 58th multiplexer U58 pin schematic diagram are as shown in Figure 5.

As seen from Figure 5, the 58th multiplexer U58 is selected according to UART2_SEL low and high level RS232 either RS485, when UART2_SEL is high level, the 55th optocoupler U55 is not turned on, and passes through the 91st Resistance R91 draws high the 58th multiplexer U58 the 6th pin for high level.

When the 58th multiplexer U58 the 6th pin is high level, Y1 and Z conductings, reception pin is switched It is RS232 modes to RS232 transceiving chips U53, that is, pattern switching, on the contrary, when UART2_SEL is low level Wait, the 55th optocoupler U55 conductings, the 58th multiplexer U58 the 6th pin be low level, and Y0 and Z are turned on, connecing Closed tube pin switches to RS485 transceiving chip U45, that is, communication mode is switched to RS485 modes.

In the present embodiment, communication switching circuit 3 also include the 20th paster magnetic bead L20, the 22nd paster magnetic bead L22, 24th paster magnetic bead L24, the 26th paster magnetic bead L26, the 59th Transient Suppression Diode D59, the 60th a flash State suppresses diode D61, the 64th Transient Suppression Diode D64, the 73rd Transient Suppression Diode D73, the 75th Transient Suppression Diode D75, the 78th Transient Suppression Diode D78, the 23rd fuse F23, the 26th fuse F26, the 29th fuse F29, the 32nd fuse F32, the 35th fuse F35, the 66th discharge tube D66A, 67th discharge tube D66B, the 71st discharge tube D71A, the 72nd discharge tube D71B, the 81st discharge tube D81A, 82nd discharge tube D81B and connector LK15.

20th paster magnetic bead L20, the 22nd paster magnetic bead L22, the patches of the 24th paster magnetic bead L24 and the 26th Piece magnetic bead L26 effectively can suppress to EMI radiation caused by RS232/RS485 progress data interactions, therefore EMI can be surveyed Examination is significantly improved.

20th paster magnetic bead L20 one end is connected with the 6th pin of RS485 transceiving chips, the 20th paster magnetic bead The L20 other end one end with the 59th Transient Suppression Diode D59, the 23rd fuse F23 one end and respectively 61 transient diode D61 one end connection, the of the 22nd paster magnetic bead L22 one end and RS485 transceiving chips U45 Seven pins connect, the 22nd paster magnetic bead L22 other end other end with the 61st transient diode D61, the respectively 26 fuse F26 one end connects with the 64th transient diode D64 one end, the 24th paster magnetic bead L24's One end is connected with RS232 transceiving chips U53 the 14th pin, and the 24th paster magnetic bead L24 other end is respectively with the 7th 13 transient diode D73 one end, the 29th fuse F29 one end and the 75th transient diode D75 one end Connection, the 26th paster magnetic bead L26 one end is connected with RS232 transceiving chips U53 the 13rd pin.

The 26th paster magnetic bead L26 other end other end with the 75th transient diode D75, the 70th respectively Eight transient diode D78 one end connects with the 32nd fuse F32 one end, the 23rd fuse F23 other end It is connected respectively with the 66th discharge tube D66A one end and connector LK15 the 4th pin, the 26th fuse F26's The other end is connected with the 67th discharge tube D66B one end and connector LK15 the 5th pin respectively, the 66th discharge tube The D66A other end, the 67th discharge tube D66B other end, the 71st discharge tube D71A one end and the 72nd are put Fulgurite D71B one end is grounded, and the 29th fuse F29 other end is another with the 72nd discharge tube D71B respectively End connects with connector LK15 second pin, the 32nd fuse F32 other end respectively with the 71st discharge tube The D71A other end connects with connector LK15 the first pin, and the 35th fuse F35 one end is respectively with the 81st Discharge tube D81A one end connects with the 82nd discharge tube D81B one end, the 81st discharge tube D81A other end and The 82 discharge tube D81B other end is grounded EARTH.

It is noted that in the present embodiment, the 59th Transient Suppression Diode D59, the 61st transient state suppress two Pole pipe D61 and the 64th Transient Suppression Diode D64 is 6.8V Transient Suppression Diode TVS, and the 73rd transient state presses down Diode D73, the 75th Transient Suppression Diode D75 and the 78th Transient Suppression Diode D78 processed are 15V transient state Suppress diode TVS, when the two poles of the earth of TVS diode are by reverse transient state high energy impact events, can be measured with 10 minus 12 power second The speed of level, the high impedance of its two interpolar is changed into Low ESR, absorbs up to thousands of watts of surge power, makes the voltage of two interpolars Clamp in a predetermined value, the precision components in electronic circuit can be effectively protected, from the damage of various surge pulses.Second 13 fuse F23, the 26th fuse F26, the 29th fuse F29, the 32nd fuse F32 and the 35th Fuse F35 is JK250 resettable fuse, can be fused when communication signal current is more than 1A, meeting when less than 1A Recovered, the protection to internal circuit when user's wrong plug external equipment can be effectively ensured in this part.67th puts Fulgurite D66B, the 71st discharge tube D71A, the 72nd discharge tube D71B, the 81st discharge tube D81A and the 82nd are put Fulgurite D81B is 10KV 90V discharge tubes, can effectively prevent surge string from entering equipment, has the function that to protect internal circuit.Connect A, B interface and RS232 transceiving chips U53 that plug-in unit LK15 is RS485 transceiving chips U45 TX, RX and GND interface patch Part.

Because RS485 transceiving chip U45 and RS232 transceiving chips U53 shares a reception pin, that is, the 43rd Photoelectric isolated chip U43 the 6th pin, the 4th pin progress for sending the 43rd photoelectric isolated chip U43 of pin access are soft Part switching control, so it is more convenient to reduce hardware cost and cost of labor, switching.

Fig. 3 is the circuit theory diagrams of power ＆ environment supervision circuit in the present embodiment, and in Fig. 3, the power ＆ environment supervision circuit includes micro-control Device U16, reset chip U22, flash chip U23 and crystal oscillator X3 processed, microcontroller U16 the 54th pin and flash chip U23 the 6th pin connection, microcontroller U16 the 55th pin are connected with flash chip U23 the 5th pin, micro-control Device U16 processed the 60th pin is connected with reset chip U22 the first pin, microcontroller U16 the 5th pin and crystal oscillator X3 One end connection, microcontroller U16 the 6th pin is connected with the crystal oscillator X3 other end.

For microcontroller U16 using the STM32F103C8T6 of ST companies as master control, reset chip U22 uses MAX809, brilliant The X3 that shakes is 8M, and microcontroller U16 working frequency is 8M, and microcontroller U16 the 54th pin and the 55th pin are IIC interfaces, flash chip U23 are GD24C512, and flash chip U23 is used to store alarm data of computer room etc..Wherein micro-control Device U16 processed serial ports UART2_RXD and UART2_TXD sends serial data as Transistor-Transistor Logic level, and UART2_CTL is microcontroller A U16 common I/O port, output low and high level receives and dispatches control pin as RS485, when UART2_CTL is high level, RS485 transceiving chips U45 sends data, and when UART2_CTL is low level, RS485 transceiving chips U45 receives data. The common I/O port that UART2_SEL is microcontroller U16 exports switching of the low and high level as RS485/RS232.

Fig. 4 is the circuit theory diagrams of power communications circuit in the present embodiment.In the present embodiment, the power communications circuit 1 wraps Include the switch chip U20 being sequentially connected, isolating transformer T1, rectifier bridge, the first filter circuit, mu balanced circuit, linear voltage stabilization core Piece and the second filter circuit.17th double diode D17, the 18th double diode D18, the 19th double diode D19, the 20th Double diode D20 form rectifier bridge, the 98th electric capacity C98, the 99th electric capacity C99, the 114th electric capacity C114 and 115th electric capacity C115 forms the first filter circuit, the 25th voltage-regulator diode D25 and the pole of the 26th voltage stabilizing two Pipe D26 forms mu balanced circuit, and the 18th voltage stabilizing chip U18 and the 24th voltage stabilizing chip are linear regulator chip, and the 100th Electric capacity C100, the 107th electric capacity C107, the 116th electric capacity C116 and the 117th electric capacity C117 form the Two filter circuits.

The power communications circuit 1 uses the isolation circuit of normal shock, and wherein switch chip U20 uses the SN6501 of TI companies, Switch chip U20, as power supply, carries out isolated from power, because isolation voltage device TI's using direct current 3.3V by isolation voltage device TI Primary and secondary umber of turn ratio is 1:2, therefore the T1 level output of isolation voltage device is the 6.6V of exchange, is limited to the volume of plank, with And RS232 and RS485 telecommunication circuit power are about 100ma~200ma, and traditional rectifier bridge volume is more huge, because This this, do not have to carry out AC rectification using traditional rectifier bridge mode in power communications circuit 1, but use two PCB to seal Fill as SOT23-3 double diode BAT54A (i.e. the 17th double diode D17, the 19th double diode D19) and double two poles Pipe BAT54C (the 18th double diode D18, the 20th double diode D20) builds rectifier bridge, reaches the effect of rectification.

By the 98th electric capacity C98, the 99th electric capacity C99, the 114th electric capacity C114 and the 110th After five electric capacity C115, using 6.1V voltage-regulator diode (the 25th voltage-regulator diode D25, the 26th voltage-regulator diode D26 voltage stabilizing) is carried out, and linear voltage stabilization is carried out after meeting the 18th voltage stabilizing chip U18 and the 24th voltage stabilizing chip U24 again below, Then again pass by the second filter circuit to be filtered, exporting two-way, the isolation 5V power supplys on ground are not powered to RS485/RS232 altogether. In the present embodiment, the 18th voltage stabilizing chip U18 and the 24th voltage stabilizing chip U24 use XC6206-5V.

The advantage of the power communications circuit 1 is to use positive activation type Switching Power Supply, and it is for flyback sourse, output Voltage characteristic and output current characteristic all it is good a lot, while for other forward converters, the power communications circuit 1 Possess small volume, the advantages that output ripple is small, and the radiation interference inside EMI is small.The output voltage ripple of the power communications circuit 1 It is minimum to reach 10mV.

In a word, in the present embodiment, due to realizing the switching of interface by software mode, thus can reduce hardware cost and Cost of labor, switching are more convenient.

Preferred embodiment of the present utility model is the foregoing is only, it is all at this not to limit the utility model Within the spirit and principle of utility model, any modification, equivalent substitution and improvements made etc., the utility model should be included in Protection domain within.

Claims (4)

1. a kind of software switching circuit based on RS232 and RS485, it is characterised in that including power communications circuit, power ＆ environment supervision Circuit and communication switching circuit, the power communications circuit are connected with the power ＆ environment supervision circuit and communication switching circuit respectively, The communication switching circuit includes the 43rd photoelectric isolated chip, the 49th optocoupler, the 55th optocoupler, more than the 58th Path multiplexer, RS485 transceiving chips and RS232 transceiving chips, the 7th pin of the 43rd photoelectric isolated chip and institute State the 4th pin connection of the 58th multiplexer, the 6th pin of the 43rd photoelectric isolated chip respectively with institute The 4th pin for stating RS485 transceiving chips connects with the 11st pin of RS232 transceiving chips, and the of the 49th optocoupler Four pins are connected with the second pin of the RS485 transceiving chips and the 3rd pin respectively, and the 4th of the 55th optocoupler the Pin is connected with the 6th pin of the 58th multiplexer, the first pin of the 58th multiplexer with The 12nd pin connection of the RS232 transceiving chips.

2. the software switching circuit according to claim 1 based on RS232 and RS485, it is characterised in that the communication is cut Changing circuit also includes the 20th paster magnetic bead, the 22nd paster magnetic bead, the 24th paster magnetic bead, the 26th paster magnetic Pearl, the 59th Transient Suppression Diode, the 61st Transient Suppression Diode, the 64th Transient Suppression Diode, the 7th 13 Transient Suppression Diodes, the 75th Transient Suppression Diode, the 78th Transient Suppression Diode, the 23rd insurance Silk, the 26th fuse, the 29th fuse, the 32nd fuse, the 35th fuse, the 66th electric discharge Pipe, the 67th discharge tube, the 71st discharge tube, the 72nd discharge tube, the 81st discharge tube, the 82nd discharge tube And connector, one end of the 20th paster magnetic bead are connected with the 6th pin of the RS485 transceiving chips, the described 20th The other end of paster magnetic bead respectively one end with the 59th Transient Suppression Diode, the 23rd fuse one end and One end connection of 61st transient diode, one end and the RS485 transceiving chips of the 22nd paster magnetic bead 7th pin connects, and the other end of the 22nd paster magnetic bead is another with the 61st transient diode respectively End, one end of the 26th fuse connect with one end of the 64th transient diode, the 24th paster magnetic bead One end is connected with the 14th pin of the RS232 transceiving chips, the other end of the 24th paster magnetic bead respectively with institute The one end for stating one end of the 73rd transient diode, one end of the 29th fuse and the 75th transient diode connects Connecing, one end of the 26th paster magnetic bead is connected with the 13rd pin of the RS232 transceiving chips, and the described 26th One end of the other end of paster the magnetic bead other end with the 75th transient diode, the 78th transient diode respectively Connected with one end of the 32nd fuse, the other end of the 23rd fuse respectively with the 66th discharge tube One end connected with the 4th pin of connector, the other end of the 26th fuse is put with the described 67th respectively One end of fulgurite connects with the 5th pin of connector, the other end of the 66th discharge tube, the 67th discharge tube One end of the other end, one end of the 71st discharge tube and the 72nd discharge tube is grounded, the 29th fuse The other end is connected with the other end of the 72nd discharge tube and the second pin of connector respectively, the 32nd insurance The other end of silk is connected with the other end of the 71st discharge tube and the first pin of connector respectively, and the described 35th One end of fuse is connected with one end of the 81st discharge tube and one end of the 82nd discharge tube respectively, and the described 8th The other end of the other end of 11 discharge tubes and the 82nd discharge tube is grounded.

3. the software switching circuit according to claim 1 or 2 based on RS232 and RS485, it is characterised in that described dynamic Ring supervisory circuit includes microcontroller, reset chip, flash chip and crystal oscillator, the 54th pin of the microcontroller with The 6th pin connection of the flash chip, the 55th pin of the microcontroller draw with the 5th of the flash chip Pin connects, and the 60th pin of the microcontroller is connected with the first pin of the reset chip, and the of the microcontroller Five pins are connected with one end of the crystal oscillator, and the 6th pin of the microcontroller is connected with the other end of the crystal oscillator.

4. the software switching circuit according to claim 3 based on RS232 and RS485, it is characterised in that the communication supplies Circuit includes switch chip, isolating transformer, rectifier bridge, the first filter circuit, mu balanced circuit, the linear voltage stabilization being sequentially connected Chip and the second filter circuit.