0 introductions
The Karamay petroleum administrative bureau heating company vigorously promoted labor controlling machine in recent years in its subordinate's several boiler room, has made the very big progress in the foundation automation aspect. But, these labor controlling machine dispersers to are apart from this company several kilometers to several dozens kilometers each boiler rooms in, each other independently disperses, thus the company control room administrative personnel must give the boiler room the technical personnel makes the phone call to understand each place running status, even goes by car to go solves the problem. Therefore, the urgent need establishes take the control room as the central long-distance monitoring network, further realizes the management automation in the foundation automation foundation. But, because its subordinate boiler room more also is very dispersible, from aspect and so on cost and operation requirements considered, uses the computer local area network the method not to be suitable. We designed (PBX) have composed a long-distance monitoring network through the telephone switchboard, maximum limit has used original labor controlling machine and the telephone network. This system may promote to the metallurgy and in other many industries control system.
1 monitoring network composition
Chart 1 shows for the monitoring network composition structure.

In the chart, in various subordinates boiler room has the PC main line 486, 586 labor controlling machine, also some around 1990 provided STD total informer controlling machine. Each bench work controlling machine control 2 ~ 6 hot water boilers, complete the data acquisition and the demonstration, the boiler water leakage temperature control, the drum wind control, the chamber negative pressure control, report to the police, function and so on data printing. After completes the monitoring network, various labor controlling machine besides completes the original control function, but also increased the correspondence function. In the hardware aspect, each bench work controlling machine installs MODEM and the telephone line is connected in, chart 1 the center dashed line expression digit dialing telephone channel, stemming from the working conditions consideration, MODEM uses sets at the type. PBX is playing the role in the network which the line exchanges. The control room will establish to install the MODEM management to use the computer, after it to some boiler room labor controlling machine digit dialing, this labor controlling machine will be connected the boiler system performance data, the establishment parameter, will report to the police the information and so on through the telephone channel (point-to-point line) the real-time transmission to in the control room computer, by the vision control supervisor observation and handling, after the control room hanging machine then digit dialing will visit another boiler room.
Below this system has the characteristic:
(1) this system is one kind of star network, borrows intelligent MODEM which the telephone network and the function consummates, simplified the hardware system and the software design, and has the merit which the convenience expands accommodates.
(2) general star network because each stand and central stand direct connected, thus electric cable expense high, installs the stand to be difficult. This system use existing PBX telephone channel, greatly saves the fishing net expense and the cycle, also the transmitting range only receives the telephone channel quality the limit. The farthest boiler room is away from above control room 20km, between the two has realized the data transmission.
After (3) the PBX telephone line enters each computer MODEM, also from MODEM multiple connection to original use telephone, thus causes MODEM and the telephone may the time sharing use identical strip telephone line. So long as correctly establishes MODEM to permit the telephone bell before the reply the number of times, then does not affect the original telephone to turn on and to split out the function.
(4) because each labor controlling machine is through the digit dialing telephone channel connection to the control room, therefore so long as has a telephone line, any has provided in MODEM and the control room the position machine procedure computer all can substitute for the control room computer, the direct digit dialing visits some boiler room labor controlling machine. This causes administrative personnel's also to be possible to use the portable computer outside control room other places to find out each boiler room current movement situation.
2 MODEM connection module software design
2.1 plans designs
Requests from the control room management to look below that, the control room computer program and the lower position labor controlling machine procedure should have the function: (1) the control room computer program ought to be able the digit dialing, thus with correlation labor controlling machine establishment connection. After (2) MODEM connects successfully, the labor controlling machine procedure should the automatic transmission real-time data to the control room. (3) the control room computer program ought to be able MODEM hanging machine, the conclusion correspondence.
Because the original labor controlling machine procedure uses is under the DOS environment programs, also the movement effect is good, therefore we used the C + + language to develop DOS under an environment MODEM correspondence class achievement independent module, in the original source program only had to increase to this correspondence class member function transfer, might control the program extension correspondence function for the original labor. Similarly, has developed the control room computer program take this MODEM correspondence class as the foundation. Therefore has not used the WINDOWS programming, on the one hand this need reestablishes all procedures, the development and the debugging cycle long, the risk is big; On the other hand, STD total informer controlling machine can provide the memory only can achieve 512KB, stored routine EPROM or the electronic plate below 1MB, is unable to satisfy moves the WINDOWS procedure hardware request.
In this MODEM correspondence control class, the data transmission and the receive has selected the severance method, in backstage execution, but the interrupt service isr installment with relieves, serial passes unguardedly sets with the MODEM initialization to this correspondence class structure function and analyzes in the construction function, thus enable it to have the very good module, the use is simple. Severs the way correspondence to be allowed to satisfy the labor to control the procedure well the timely request. Generally speaking, in the serial communication, the data receive selects the severance method, but the data transmission already may select the inquiry method, also may select the severance method. When uses the inquiry way transmission data, the signal procedure design quite is simple, but in the data sending process must unceasingly monitor UART (general asynchronous transmission/acceptor) the line condition register, waited for the register demonstrated may hand down a data byte the signal, has cost the massive CPU time, therefore only uses to each time transmits minority according to the situation. This system labor controlling machine through the speed is the 14.4KB MODEM transmission real-time data, the size in several kilobyte to several kilobyte about, each time transmits needs for several seconds to several seconds. Very obviously, if uses the inquiry way transmission, then data transmission period labor controlling machine cannot normally carry out function and so on data acquisition and control, from the user contact surface looked cannot carry out any keyboard and the mouse response, is similar of "dying machine" condition. But severs the way is one kind of highly effective correspondence condition, each time transmits when the data only must put in the data the transmission buffer, then sends in the 1st byte to the serial mouth to trigger the character transmission severance sequence, other bytes transmissions complete by the center legal precedent regulation, thus extricates the master routine.
2.2 MODEM correspondence class design
The signal procedure programming quite is generally complex, when selected the severance method in particular and has used MODEM. In order to enhance the modular degree, we have fully used the C + + object-oriented programming (OOP) the method.
First, and the serial communication related data and the behavior way seal in a base class, and will derive a MODEM correspondence class in this foundation; Next, the serial mouth and the MODEM initialization, center the legal precedent regulation installment reconciliation except and analyzes in the construction function in the MODEM correspondence class structure function to complete; Moreover, sealed to the correspondence class center legal precedent regulation centralism has completed the data transmission, the receive, and monitored the MODEM connection and the separation condition change, but did not need the master routine the intervention. Severs the way to accept the data a difficulty is: The receive character already possibly issues MODEM the AT order result code, also possibly is the general character which another computer transmits. Through monitors the MODEM condition change severance and the inspecting office receive character class, this correspondence class realized has automatically differentiated to two kind of characters and lays aside in the different buffer. The master routine may directly obtain the AT order result code or the receive general character from the buffer.
Designs after above, finally obtains the MODEM correspondence class and its the main member function synopsis is as follows.
Class EnComm //MODEM correspondence class.
{
Public:
EnComm // structure function: Completes the serial mouth and the MODEM initialization, the installment severance vector, the severance shield and so on.
(Int PortAddress,
Int IntNumber,
Void interrupt (far *IntHander) (...) ;
~ EnComm (); // analyzes the construction function: The MODEM replacement, restores the severance vector and so on.
Int SendConfigureString // disposition function: And returns to the MODEM transmission initialization character string carries out the result.
(const char*ConfigureString,
Float WaitSecond=1,
Int CheckResult=0);
Int Dial// digit dialing function: Orders the MODEM digit dialing and returns carries out the result.
(const char*PhoneNumber,
Float WaitSecond=60,
Int CheckResult=0);
Int HangUp // hanging machine function: Orders MODEM hanging machine and returns carries out the result.
(float WaitSecond=2,
Int checkResult=0);
Int GetModemStatus (void); // returns to the MODEM condition: Order condition or connection condition.
Int SendBinData// transmission function: Puts in the transmission buffer and the start transmission severance the data.
(char *DataBuffer,
Int Count);
Int GetReceiveData // receive function: Reads from the receive buffer takes the receive character class.
(char*Buffer,
Int Length);
};
2.3 correspondences programming several main points
2.3.1 serial initialization
The supposition serial passes unguardedly the base address is CommPort (generally is 0x2E8,0x2F8,0x3E8 or 0x3F8 four one), when serial mouth initialization must carry on the establishment to the UART following register.
Baud rate register (CommPort; CommPort+1): Establishment baud rate.
Line control register (CommPort+3): The establishment character length, stops the position integer and the parity check type.
Interrupt control register (CommPort+1): The permission transmission maintenance register spatial, accepts data preparation, the MODEM condition change, to accept the data to be wrong and so on many types severance.
MODEM control register (CommPort+4): (Data terminal is ready) and RTS DTR (request transmission) the position 1, 3 sets at Bit 1 to permit the severance.
Establishes when the register should first establish the baud rate register, because has these two registers 要求线to control the register 7th is only 1, then controls the line the register the 7th position 0, like this may correctly visit all following registers.
2.3.2 correspondences severances event processing
Because simultaneously permits the many kinds of types the severance, therefore in design serial communication time legal precedent regulation must in as soon as start to examine the severance to symbolize register Bit 2 and Bit 1 determines the severance event the type. The identical time possibly has many severances, for this, with severs the sign register Bit 0 to judge the unnecessary severance whether is at the unsettled condition. When two or many severances synchronizes presses down the table the order to carry on processing, causes the original severance to be at "abolishes" the condition. Returns front the center legal precedent regulation, must process the unnecessary severance.

2.3.3 MODEM initialization character string and correspondence data check
When to MODEM initialization, must be MODEM establishes an appropriate initialization character string, disposes CD (carrier examination) and DTR (data terminal preparation is ready) the examination signal control way, the mistake controlling agreement and the data compression agreement and so on, by maximum limit displays uses MODEM the hardware working ability [ 2 ].
In order to guarantee the correspondence data transmission the integrity and is correct, besides uses MODEM the error correction function, also must carry on the data check and error correction processing in the software design. In the real time data transmission, transmits the data the position machine procedure uses in the value by the control room in to demonstrate and the curve demonstrated, and the data is the periodic return transmission (week contract is 5s), in order to sees the data in the control room the real-time change. The lower position labor controlling machine procedure to the data which each time transmits by the under form code packs:

Among them, each time transmits effective real-time data approximately 5KB, the character strings together DATASTART and DATAEND takes the effective data the outset and the end mark. In the data packet also includes the effective data the length as well as the arithmetic and the verification code. On the position machine procedure carries on the decoding to the real-time data package, and examination actual receive effective data whether does conform to the data length as well as the verification code condition, decided accepts or discards this number of times according to. Because the real-time data transmission periodicity and the folk remedy to, discard the data which occasionally makes a mistake not to be able to have the tremendous influence. This kind of verification plan does not request the data which reissues makes a mistake, thus both may satisfy the operation requirements, and greatly simplified the programming difficulty.
3 concluding remark
This system realized by a smaller investment has used in the long-distance correspondence monitoring function which was daily routinely to each boiler room inspects, kept abreast of the boiler movement situation, the measuring appliance damage situation, the staff to the boiler movement maintenance situation and so on. Because in the heating company control room computer has provided on position machine procedure which corresponds with the subordinate boiler room various labor controlling machine procedure, after puts through some labor controlling machine several seconds, the administrative personnel then to face in the control room with the labor controlling machine procedure quite same not less than man-machine contact surface, observes subordinate boiler room various parameter the and so on boilers temperature, pressure value and the change curve, reports to the police the information and so on, may complete in several minutes to a boiler room inspection; When evening breaks down, the technical personnel may inspect the partial accident cause factor in the home through the telephone line. After for a year use, the system function and the reliability underwent the test.

Author synopsis: Liu Xiao is good, male, 191 years are born, the teaching assistant, mainly is engaged in labor automation specialized the teaching, scientific research and research work and so on industry control machine application.