Protel 99SE in circuit design

                  With the rapid development of the electronics industry, the application of large-scale integrated circuits has become more and more common. Electronic design automation EDA (EleetrONic Design Automation) has become an irreversible trend. Protel is a set of EDA development tools built into the PC environment. Since 1991, Protel has become the design software of choice for a wide range of circuit designers.

Protel 99SE is the sixth generation of Windows-based products introduced by Protel Technology in 2000. Its main functional modules include circuit component design, circuit schematic design, printed circuit board design, package component design, and circuit simulation. Wait. This paper mainly describes the application of Protel software in the design of electronic clock circuit.

1 Protel software design features and processes

Protel software has powerful circuit simulation capabilities, can achieve analog-digital mixed-signal simulation analysis, can provide continuous analog signals and discrete The simulation of digital signals, and can analyze the performance of various aspects of the circuit, such as the AC and DC characteristics of the circuit, temperature drift, noise, distortion, tolerance, worst case and other characteristics. Protel provides a set of setup parameters for each type of analysis, and the setup dialog allows you to easily set the various parameters you need. Protel offers more than 20 libraries of analog and digital device simulation components, including more than 6,000 common components. At the same time, Protel provides an open library maintenance environment where users can easily modify existing device models or create new device models.

1.1 Circuit Design and Schematic Design Flow

Circuit design refers to the realization of an actual electronic product from concept design, circuit design to physical structure design. The schematic design is mainly to draw a correct and perfect circuit schematic, drawing the circuit schematic is the basis of the entire circuit design. The schematic diagram of the circuit schematic design is shown in Figure 1.

circuit diagram of FIG. 1 design flow

1.2, and printed circuit board design flow

is a printed circuit board design becomes a circuit diagram from The important steps of a specific product, the printed circuit board is directly related to the actual product. Therefore, printed circuit board design is the most important and critical step in circuit design. Usually the printed circuit board design process is shown in Figure 2. 2 a flowchart of FIG.

printed

2 Protel Circuit and its examples

FIG main circuit board design is below the minimum system microcontroller design of the circuit will be described Protel 99SE Specific applications in the design.

2.1 Circuit Schematic Design

The most basic requirement of circuit schematic design is correctness, followed by reasonable layout, and finally correctness and aesthetics under the premise of reasonable layout. Sexuality and readability.

According to the above circuit schematic design flow, the minimum system schematic design process of the MCU is as follows:

(1) Set the schematic design environment. The design environment is the preliminary work of drawing the schematic. Before the schematic drawing, the design environment should be set. The working environment settings are made using the menus Design/OpTIons and Tool/Preferences. The settings of the drawing schematic environment mainly include drawing size, snap grid, electrical grid, template settings, and so on.

(2) Place components. Place electrical and electronic components on the drawing. In general, the schematic symbols of the components can be found in the component library. Only the components in the component library need to be taken out of the library and placed on the map. Due to the wide variety of components, they are placed in different component libraries, so you should know the types of components in each component library during use.

(3) Schematic wiring. Once the component is placed behind the schematic, it is necessary to connect the components with wires, and the electrical rules must be met when connecting. In the case of structured design, in order to make the graphics clear, you can use network label connections.

(4) Editing and adjustment. Edit the properties of components, including component names, parameters, package drawings, and more. Adjust the position of components and wires, etc. At the same time, the circuit's labeling and description should be added where necessary.

(5) Check the schematic diagram. Use the electrical rules check function of Protel 99SE to check whether the connection of the schematic is reasonable and correct, and give an inspection report. If there is an error, it needs to be corrected according to the error situation.

(6) Generate a network table. A network table for generating a schematic diagram, which is a connection list between a component name, a component package, a parameter, and a component, by which each component and a connection relationship therebetween can be confirmed.

(7) Printout. Printout schematic.

After the above steps, the design of the minimum system schematic of the MCU is completed. The circuit of the minimum system of the single-chip microcomputer is relatively simple, including the crystal oscillator circuit required for the operation of the single-chip microcomputer and the single-chip microcomputer, the power-on automatic reset and the manual reset circuit, the power supply circuit and the programming interface required for the operation of the single-chip microcomputer. The schematic diagram of the minimum system of the completed MCU is shown in Figure 3. FIG 3

smallest SCM system circuit diagram

2.2 printed circuit board design

is the ultimate goal of circuit design to design electronic products, electronic products and The physical structure and circuit functions are realized by printed circuit boards. The process of designing a printed circuit board using Protel 99SE is as follows:

(1) Start Protel 99SE and enter the printed circuit board design environment.

(2) Circuit board frame design. Before the printed circuit board design, first have a preliminary plan for the circuit board, such as the frame size of the circuit board, using several layers of circuit boards, whether it is a single panel or a double panel, what kind of package form and installation position of each component, etc. . According to the design of the circuit, the size of the board drawn in Keep Out Imyet is 7617mil wide and 4466mil high. The board is defined as a double panel. The size of the board is the first factor to consider when designing the board. Generally, the board's external dimensions are matched with the product's housing design. The ratio of length to width is designed to be 4:3 or 3:2 when possible.

(3) Parameter setting. Mainly set the layout parameters of the components, board parameters, wiring parameters and so on. Generally, some parameters can be used with their default values. Parameter setting is a very important step in the design of the printed circuit board. Execute the menu command Design/Rules, left click on the Routing button, and set the parameters in the rules class (RulesClasses) according to the design requirements. . Select Routing Imy-er. Select WIDTh ConSTraint to set the ground line width: Left click on the Add button to enter the line width rule setting interface. First select Net in the Filter Kind selection box in the Rule Scope area, then select GND in the Net drop-down box. In the Rule Attributes area, set the line widths of the Minimum width, Maximum width, and Preferred input boxes to 50 mils; the power line width setting is VCC in the Net drop-down box, and the other line width settings are the same; the entire board line width setting : Select Whole Board in the FilterKind selection box, and then set the line width of the three input boxes of Minimum width, Maximum width and Preferred to 20mil.

(4) Transfer to the network table and add component packaging. The network table is a rule that guides the automatic routing of printed circuit boards, and is also the intermediate carrier between the circuit schematic design system and the printed circuit board design system. For each component that is loaded, it must have the correct shape package to ensure smooth circuit board layout. Execute the menu command Design/Add/Remove Library, select the component package library corresponding to all components in the “Add/Remove Component Library” dialog box, then execute the menu Design/Load Nets command, and then click in the pop-up window. “Browse” button, and then select the network table file generated by the schematic design (extension Net) in the pop-up window, if there is no error, click the "Execute” button. If an error message appears, you will need to change the error until all errors are correct.

(5) Arrange components. The Protel 99SE allows for automatic placement of components and manual layout. Layout is a very critical step in routing. In order to make the layout more reasonable and beautiful, most designers use manual layout. Sometimes users can achieve automatic layout in order to improve wiring efficiency under less stringent conditions.

(6) Automatic wiring. The Protel 99SE features the world's most advanced network-free, shape-based diagonal auto-routing technology. Execute the menu command Auto Routing/All, and click the Route all button in the pop-up window, the program will automatically route the printed circuit board. As long as the relevant parameters are set properly and the component layout is reasonable, the success rate of automatic routing is almost 100%.

(7) Manual adjustment. After the automatic routing is over, there may be some unsatisfactory places that can be manually adjusted to make the board perfect. Finally save the file and print out the printed circuit board (PCB) diagram as shown in Figure 4. FIG 4 is provided

completed PCB electronic timepiece FIG

Protel 99SE Support The PCB design is completed is converted to a 3D view, in order to check the various aspects of the circuit board layout, and the like trace Happening. In order to find the problem and make the corresponding changes. The 3D rendering of the minimum system board of the MCU is shown in Figure 5. FIG 5

smallest SCM system circuit board 3D renderings

PCB production-processing enterprises, the finished smallest SCM system circuit board shown in Fig. FIG 6

finished microcontroller minimum system board

3 Conclusion

With the rapid development of modern electronic information technology, the complexity of electronic products and the degree of integration has A rapid increase. In the electronic product design process, the use of circuit design software is also becoming more widespread. Protel 99SE provides a complete process from schematic drawing, netlist generation and board design. With its powerful features, it greatly improves product reliability, shortens design cycle and reduces design cost. Computer-aided electronic circuit design software will continue to do so for a long time to come.