The abstract discusses the ProfIbus-DP agreement structure, the correspondence mechanism mansion technology characteristic in detail, and unifies the Profihus-DP technology and the embedded technology, develops the high openness, timeliness and the reliable Profibus-DP master station.
Key word field bus Profibus-DP master station VxWorks
The field bus is now one of automated domain hot spots, its appearance symbolizes the industrial control area of technology another new times start. In the numerous field bus product, open style field bus Profibus which was second to none as Europe (Process Fieldbus) was already accepted by the world, becomes the internationalization the open style field bus standard, and became field bus’s two big systems with foundation field bus FF, widely applied in the processing manufacture, the process and the building automation domain.
The embedded system take application as the center, the software and hardware may cut out, is suitable for the application system to the function, the reliability, the cost, the volume, the power loss has the strict request situation, its application spreads the industrial control, the military, the network, the information electrical appliances, the finance and so on each domain.
Unify the Profibus-DP technology and the embedded software and hardware the big lift system’s quality, enhances system’s openness, timeliness and the reliability.
1 Profibus-DP agreement structure and technical characteristic
Profibus may divide into according to the application characteristic: Profibus-FMS (Fieldbus Message Specification), Profibus-DP (Decen-tralized Periphery) and Profibus-PA (Process Automation) three compatible editions.
Profibus-FMS uses in completing the workshop level versatility communication task, is suitable in the medium transmission speed monitoring network as well as too the scope complex communications system. Profibus-DP uses in realizing the equipment first-level high speed data correspondence, the central controller carries on the correspondence through the high speed serial line and the dispersion field apparatus, is one kind high speed, the low cost communications system, is suitable in the distributional control system’s high speed data transmission. This kind of systematic constitution including the DP 1 kind of master station (DPMl, central programmable controller), the DP 2 kind of master stations (DPM2, programmable, configuration, diagnosis equipment) and DP from stands (carries on input/produce information gathering/transmission equipment). Profibus-PA is Profibus-DP to scene extending, it has the essential security characteristic, is suitable in the essential safety requirements high situation and the main line power supply stand.
The Profibus agreement structure carried on certain simplification on the OSI reference model, agreement structure like chart l has shown, this kind of structure has guaranteed fast and the effective data transmission as well as system’s low cost.
Profibus-DP has used the physical level, the data link layer and the user level. The physical level has stipulated the line medium, the physical connection type and the electrical specification. Profihus-DP usually uses the RS485 transmission technology, the transmission medium double twists the copper cable for the shield, the transmission speed may reach 9.6 kbps~12 Mbps. In the electromagnetic interference is very big or in the transmitting range very long situation, may use the fiber optic transmission technology.
Field bus data link layer FDL stipulation medium access control, frame form, service content as well as physical level, data link layer main line supervisory service FMAl/2. The medium access control (MAC) level described the mix access mode which Profibus uses, namely between the master station and the master station token transfer mode, the master station with from the station host one from the way, the master station obtains the visit domination through the gain token. Profibus stipulated that the frame character is composed of 11: Starts position O, 8 bit data, occasionally to verify the position and stop position l. The FDL level provides 4 kind of services: SDA, SRD, SDN, CsRD. The DP main line’s transmission depends upon SDN and SRD these two kind of FDL service. The FMAl/2 function mainly has forces to reposition FDL and PHY, the hypothesis parameter value, reads the condition, to read the event and to carry on the disposition and so on.
User level including immediate data link reflection DDLM and user interface/user. The user interface explained in detail each kind of different Profibus-DP equipment’s equipment behavior, DDLM will possess the function which transmits in the user interface to map field bus data link layer FDL and the FMAl/2 service.
2 Profibus-DP correspondence mechanism
What Profibus-DP main date is with certain simple carries on the fast circulation in the function formidable master station from the station the data exchange, therefore the system mainly completes main one from the communication task, in addition the Profibus mix main line access mode also permits between 1 kind of master station and a 2 kind of master station host host correspondence.
In the Profibus-DP system. DPMl and DP mainly have from the station correspondence type: The read from the diagnostic message which, the parametrization establishment and the configuration, the circulation user data exchange stands. Profibus-DP main one from course of communications, may divide into the following several stages approximately: The master station to from the first diagnosis which stands, the parametrization from the station, the configuration disposition from the station, the master station to from the second diagnosis which as well as the master station and from the station for data exchange stands.
Regarding the multi-master station communications system, between DPMl and the DPM2 correspondence includes: Reads related DP from the diagnostic message which stands, the parameter upload and downloading, activates the main line parameter (not to need confirmation), includes violently with relieves includes the parameter collection violently, chooses DPMl the operator schema and so on. DPM2 with from the station correspondence for the non-circulation, including the read from the correspondence connection disposition which, the input/output data and the establishment stands from the station address.
3 Profibus-DP field bus master station system design
Profibus is the open standard. In principle, this agreement may realize on any processor, in processor interior or exterior installment asynchronous serial communication connection (UART) then. Based on the above characteristic, when develops the Profibus-DP master station, mainly has the following two kind of solution:
①Realizes by the microprocessor movement complete agreement stack. This kind of plan realizes the Profibus agreement completely by the software, the development entire agreement stack software difficulty is very big, majority exploiters generally to special developer purchase.
②Realizes in addition by the agreement ASIC chip its expansion solidification procedure. This kind realizes the plan uses most one kinds, realizes the Profibus agreement data link layer medium access control function by the special-purpose ASIC chip; But data link layer’s other functions move by the microprocessor its expansion solidification procedure to realize. At present may use in this kind of plan the ASIC chip mainly having 3 kinds: Sie-mens Corporation’s ASPC2, M2C Corporation’s IXl and IAM Corporation’s PBM. When applies this plan realizes the master station, may have two kind of choices: First, purchases the complete development platform to above 3 companies, including the ASIC chip, solidification procedure as well as corresponding hardware and development software; Second, only purchases the ASIC chip as well as the essential software and hardware development kit, the solidification procedure realizes by own compilation, this law development difficulty is big, the development cycle is long. Uses the latter to realize the master station typical example is HMS Corporation, has used Siemens by its development’s Anybus-M master station module Corporation’s ASPC2 chip, but the expansion solidification procedure compiles by HMS Corporation, after composing a complete module, provides for other exploiters. In order to reduce the development cycle, this master station’s design is uses HMS Corporation’s Anybus-M master station interface module, thus reduces when sets up the DP master station software and hardware aspect work load.
What this design sets up is the Profibus-DP single master station system, an5rbus-M module when the initialization may establish is DPMl and DPM2, therefore develops the master station besides realizes DPMl and DP one (including reads DP from the station host from the function from diagnostic message which, establishment stands from station parameter, correspondence connection disposition inspection, for data exchange as well as overall situation control command), but must realize DPM2 and DP from the host who stands - from the function (including read from correspondence connection disposition which, input/output data stands, establishes from station address and so on).
3.1 hardware designs
Profibus-DP master station hardware circuit diagram as shown in Figure 2. The system hardware mainly by based on PC/104 main line’s CPU module SCM7020B, the Anybus-M module, the CPLD logic decoding circuit and the reset circuit is composed.
The Anybus-M master station interface module through DPRAM with the exterior processor connection, PC/104 realizes the master station regarding this through the DPRAM visit with from the data exchange which stands, as well as to master station module access control. Solves PC/104 and the Anybus-M master station interface module through the interrupt or the BUSY holding wire simultaneously visits DPRAM the conflict question. CPLD uses in realizing the address decoding, produces selects patches or strips of land as worth saving for seed signal CS and reads/writes the control signal. The reset circuit uses in realizing PC/104 and the Anybus-M module replacement.
3.1.1 Anybus-M master station interface module
The Anybus-M master station interface module already realized the essential network protocol, on the board has brought the microprocessor, the independence completes the communication protocol in the automatic equipment, simultaneously supports DP and DPVl, has 4KB DPRAM, has guaranteed the most 1536 byte circulation input/output data high speed transmission. In addition, this module may integrate in the industrial automation equipment, realizes with the industry scene installment correspondence, typical application including man-machine contact surface, PLC, numerical control equipment, robot as well as intelligent visualization equipment and so on.
Figure 3 is the Anybus-M master station module internal structure diagram, divides into the application program interface and the field bus connection two parts.
①Application program interface. The module and microprocessor’s connection is 4KBDPRAM. DPRAM acts according to its application to divide into the following several regions: Input/Output Data Area, the application procedure reads in the transmission to the Input region for from the data which stands, from Output region read receive from station data; Mailbox Input/Output Area, the application procedure carries out some concrete operations through the transmission mailbox order instruction module (for example initialization, read from station diagnosis, establishment from station address and so on), simultaneously outputs the region read module from the mailbox the response; Fieldbus Specific Arc, a, this region saves the master station and from the station network information, like from station configuration tabulation, data transmission tabulation, from station diagnostic listing, master station condition table and so on; Corltrol Register Area, this region information and so on storage module edition information, initialization parameter, field bus type, event notice reason; Handshake Registers, uses in the region the assignment and the recycling, the event notice, the transmission/receive mailbox order and so on.
②Field bus connection. This module has completed the field bus first floor agreement not to need the application procedure the intervention; Provides a RS485 connection, connects through this connection the module in the Profibus-DP network.
3.1.2 based on PC/104 main line’s CPU module SGM7020B
PC/104 takes one kind specially the industrial control main line which defines as the embedded control, is one kind of optimized small storehouse type structure embedded control system. Its volume is small, the structure is compact, may insert to the volume and in the power loss request high product, at present applies in the industrial control domain is getting more and more widespread.
SCMT020B uses the PC/104 main line’s embedded microprocessor, it integrated the 10/100Base-T ethernet connection and the high performance graphics processor in the board; Uses the x86 compatible 64 sixth generation of processor, the highest running rate may reach 300 MHz, its memory address D2000~DFFF(8KB), C8000~CFFF (32 KB) idle, may assign for exterior expands RAM; Interrupts IRQ5, IRQ9, IRQl0 available, may external connection other interrupt sources.
3.2 software designs
The software design is the entire master station design key and the difficulty. In order to enhance overall system’s timeliness and the reliability, moves in the world on PC/104 widespread use 32 real-time operating system VxWorks. The software design mainly completes the VxWorks device driver the compilation, the network configuration hypothesis and downloading as well as the Anybus-M master station module access control.
3. 2.1 VxWorks device driver compilation
The application procedure carries on the data communication through the driver and the hardware. The driving system hardware work is completes by BSP, in the BSP actuation program management specific goal environment’s equipment, carries on the control and the initialization to it. BSP provides to VxWorks with the hardware environment connection, completes adds when the electricity the hardware initialization responsibly, is the VxWorks visit hardware driver provides the support, has nothing to do with the hardware carries on the integration Vx-Works in with hardware related as well as the software which.
3.2.2 network configuration hypothesis and downloading
The network configuration may Anybus which provides through Anybus the Net-Tool disposition software realize, may also order (mailboxmessage) through the mailbox to realize.
Anybus NetTool matches the clamour software based on the Windows environment, realizes through the dragging and drop and dropping type operation to the Profibus network disposition and the optimization. In addition, this tool also has to the I/O data monitor, the revision and so on online diagnosis function, in this independent disposition may take Windows the OCX module integration in the third party software. (The RS232 serial interface) may download through Anybus-M master station module’s ConfigurationInterfacc disposes the good result.
The transmission mailbox command mode needs the development personnel to be familiar with the Profibus-DP communication protocol the nuts and bolts, carries on the disposition to the network entire configuration, establishes the master station main line parameter collection, the master station user parameter collection, from the station parameter collection, the configuration data set, the input/output address assignment, the input/output data form and from the station user data unit collection and so on, and loads in the application procedure through the transmission mailbox order the database to the module.
3.2.3 Anybus-M master station module access control
The Anybus-M master station module provides to application procedure 4 KB/2KB DPRAM, the application procedure realizes through DPRAM to the master station module access control. The application procedure divides into following several parts.
①Initialization routine module: Including hardware initialization and software initialization. The hardware initialization including the DPRAM inspection, carries on the hardware check through the mailbox order. The software initialization uses in establishing the elementary operation eo parameter, like DPRAM input/output length, operator schema, DPRAM pattern (4KB/2 KB) and so on.
②Interrupt handling routine module; When receives the signal of stop, the read handshake register’s content, the judgment has the interrupt reason (for example event notice, mailbox notice, module by initialization, start interrupt, region assignment response and so on); According to the reason for abort, changes over to the different interrupt handling routine.
③Master routine module: Circulates transfer mailbox processing in the master routine and the data exchange procedure. The mailbox disposal procedure is responsible to transmit the mailbox order and the read response message; The data exchange procedure is responsible for the master station read/writes from the station data, as well as essential control register region visit.
Conclusion
At present, the overseas Profibus-DP research development are many, the application is widespread, but the domestic application is restricted in much to the foreign product system integration, particularly aims at the Profibus-DP master station product the research development to be really few, therefore develops has the proprietary intellectual property rights master station to have the significant significance. This article in studies the ProfIbus-DP field bus standard, the main line agreement, in the embedded technical foundation, proposed the high timeliness, the redundant reliable Profibus-DP master station realizes the plan. Conforms to the international standard Profibus field bus’s promoted application, may solve in conveniently the computer supervisory system the different factory product interconnection question, to the computer supervisory system to “take the monitoring equipment as the object distributed, the direction develops based on isomerism system interconnection’s distributional supervisory system” has the important promotion effect.
