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Protel 99 . . . much more than a PCB design tool Protel 99 is much more than just a printed circuit board design tool. Among its many features, it provides automatic design checking, circuit simulation and the ability to preview the completed board in 3D. And of course, it can take a circuit diagram and automatically lay out the board for you. vantage of Windows’ improved mem­ ory management and user interface. Protel 99, the latest offering, is packed with all the features that any designer could wish for and at first sight is simply overwhelming. There are so many features that it is just not possible for us to cover them all in a review of reasonable length. Instead, we’ll concentrate on the key elements and see how they work together. By PETER SMITH In Protel 99, circuit diagrams are drawn using the “Schematic Capture” (or Schematic Editor) module. These schematics are drawn in a familiar WYSIWYG (what you see is what you get) format. If necessary, complicated designs can be simplified in appearance because Protel 99 has the ability to organise and display designated circuit sections as blocks. This is particularly handy when dealing with complex circuits that extend over many pages. The symbols of all commonly used components (over 60,000 of them) are supplied in libraries (see Fig.1). These libraries can be modified and expand­ ed using the integrated library editor Printed circuit board (PCB) design has come a long way since Protel’s Easytrax first appeared. This simple yet effective DOS-based package, along with the more advanced Autotrax, gained much popularity back in the 1980s and they’re still in use today. Until Protel arrived on the scene, PCB layout and most similar EDA (Electronic Design Automation) tasks had been the exclusive domain of UNIX-based software running on minicomputers and mainframes. This kind of hardware was out of the question for small operations, so layouts 4  Silicon Chip 4  Silicon Chip had to be done manually. Manually laying out PCB designs is laborious, involving the use of stencils, black tape and scalpel on paper or transparent sheets. As with text from a typewriter, editing the completed output is nigh on impossible. By attacking the problem from the designer’s viewpoint, Protel came up with an effective system that ran on available desktop hardware and cost a fraction of the price of high-end solutions. Later, Protel were one of the first companies to develop EDA applications for Windows, taking ad- Schematic capture and free updates are available on a regular basis from Protel’s website. Point-to-point connections can be made both manually and automatically. In automatic (or “AutoWire”) mode, it’s a simple matter of clicking on the start and end points and the connection is automatically routed (see Fig.2). In manual mode, “hot spots” at each connection point make sure that the wires actually connect, allowing the user to work at a lower zoom level than might otherwise be possible. Designs are edited using standard Windows concepts (cut, copy, paste, drag, etc). Multi-level undo/redo is also supported – a feature that I find indispensable. As you might expect, designing with a program such as Protel 99 brings many advantages. One of these is the ability to perform automatic checks on your schematic design before moving to the PCB layout phase. Protel 99 includes an Electrical Rules Checker (ERC) that examines designs for common drafting errors such as unconnected power/ground pins, floating inputs, duplicate component references, etc (Fig.3). Any problems that are identified can be highlighted directly on the schematic so that they can be easily spotted and fixed. Fig.1: browsing the schematic component libraries. Over 60,000 symbols are supplied, ready to be placed on the diagram. PLD design PLD (Programmable Logic Device) design often goes hand-in hand with the schematic layout and Protel 99 has the bases covered here too. So let’s have a quick look at PLD basics and the support offered by Protel 99. It is rare to see designs these days that consist of just a few logic devices like the 74xx or 40xx series. As miniaturisation techniques advance, chip manufacturers are squeezing more and more onto silicon wafers. Consider a typical PC motherboard for example – almost all logic external to the microprocessor is contained in just two or three chips (commonly referred to as the “chipset”). The functions of these “super” chips are fixed (or hard-wired) at the time of manufacture. But although this is the most cost-effective method for volume production, what about small production runs or prototypes? PLDs fill the gap. These devices integrate from just a few to many thousands of logic functions (or building Fig.2: using the AutoWire function to automatically connect two nodes in the Schematic Editor. Fig.3: setting up the Electrical Rules Checker. It checks the design for common drafting errors. blocks) onto a single chip. As shipped from the factory, PLDs are effectively “blank” (much like EPROMs) and must be programmed to connect their building blocks in a meaningful way. This technique allows the circuit designer to significantly reduce the physical size, power consumption and cost of the end product. Using PLDs in any design requires selecting a suitable device, then defining its internal logic connections (and hence its overall function) by using a dedicated programming language. One of the most popular is the CUPL Hardware Description Language. These high-level language instructions are then compiled into binary format, ready for download to a PLD programmer. Protel 99 greatly simplifies PLD January 2000  5 Fig.4: Protel 99 running a circuit simulation for a 555 timer IC which has been “wired” as a monostable multivibrator. language file, which is then compiled ready for PLD programming. Circuit simulation Fig.5: browsing the PCB component footprint libraries. design by allowing the engineer to draw a schematic representation of the internal logic connections, rather than having to define them with a programming language. It then automatically translates the schematic into a CUPL Simulation provides a means of verifying a design before it is even proto­typed. Protel 99’s simulator is based on the latest SPICE kernel. SPICE is the industry-standard analog circuit simulator. Developed at the University of California and released to the public domain in 1972, it has since undergone several revisions and is currently at major release 3. This release forms the kernel of most SPICE-compatible simulators. SPICE simulators can perform a host of functions, including transient, noise, distortion and Fourier analyses. They can also calculate local poles and zeros for transfer functions, calculate DC operating points and find signal transfer functions. Designing A Typical PCB In Protel 99 (1)  Define project concept. (2)  Schematic capture – the circuit is drawn and edited. (3)  Schematic design verification – errors like floating inputs and unconnected power pins are automatically detected. (4)  Circuit simulation (optional) – all or part of the circuit is simulated and the results analysed to ensure that it functions as expected. (5)  PCB layout – design information is transferred from the Schematic Editor to the PCB Layout Editor. Components are then placed and tracks are routed manually and/or automatically within the editor. (6)  PCB design verification – rules are applied to ensure design integrity and manufacturing viability. (7)  Result – output files are generated ready for direct input to the PCB manufacturing process. 6  Silicon Chip Simulating mixed analog and digital circuits in some simulators requires that the designer insert A/D and D/A converters between the analog and digital sections. In Protel 99, this process has been made more straightforward because direct support is provided for simulating digital circuits. Three steps are required to perform a simulation in Protel 99. First, the circuit schematic is drawn using the components supplied in the simulation libraries. Second, all the signal sources (AC/DC power, input signals, etc) that would be present in the real-world situation are added and finally, the simulation is run. The results are displayed in easy-to-interpret graphical form. Protel 99 includes a library of 5800 simulation-ready components, each linked to a standard SPICE model. In addition, component manufacturers usually provide SPICE models of their analog components (as files) and these can be used to update or expand the existing Protel 99 libraries as necessary. PCB layout – it’s automatic Now we really come to the heart of the matter. With the schematic design complete, wouldn’t it be nice to make use of all the information on how everything is connected together for the PCB design phase? Well, the people at Protel are more than one jump ahead of us here. Protel (and other) companies have designed PCB layout software that can import connection and component package information from the schematic, place the components on a board layout and connect them together – all automatically if desired. But let’s take a step back for a moment to the schematic entry phase. Each component in every schematic has various attributes associated with it, such as position in the schematic (X and Y coordinates), designator, library name, footprint, etc. It is the “footprint” attribute that we are interested in here, as this name assigns an appropriate footprint (or template) to the component for use during PCB layout. Component footprints are simply groups of correctly sized and spaced pads, together with overlays to suit System Requirements Protel 99 runs on Windows 95/98 and NT4. The minimum hardware requirement is a Pentium-class PC with 32MB of memory, SVGA display at 800 x 600 resolution with 256 colours and 200MB of free hard disk space. However, while Protel 99 will run on the minimum hardware spec­ified, we agree with Protel’s recommendation of a Pentium-II class PC, 64MB of memory, SVGA display at 1024 x 768 resolution with 16-bit colour and 300MB of free hard disk space. the pin size, spacing and package outlines (Fig.5). Each footprint is given a descriptive name, such as “TO-92A” (a typical small transistor package). Protel 99 also includes a PCB Lib­ rary Editor, complete with a component creation Wizard, for modifying and expanding the PCB footprint lib­raries. Updates are also available from the Protel website. Look Mum, no hands! When a schematic design is completed, a list of all the components used, their footprints and how they are connected (called a “netlist”) can be exported from the Schematic Editor into PCB layout software. Protel 99 provides a direct link between its schematic and PCB editors, so separate import and export steps are not required. Instead, the “Design Synchronizer” performs this function, as well as keeping the schematic and PCB layouts “in-sync” as the project progresses. By using the Design Synchronizer, modifications to the schematic layout are immediately reflected in the PCB layout (Fig.6). We should also mention here that the schematic and PCB layouts are “linked” in another important way. With a click of the mouse, the designer can jump from a particular point in the circuit schematic to the same point in the PCB layout and vice-versa. This is called “cross-probing” and it saves a lot of time. is done either by using the Board Wizard (which includes a handful of predefined board templates) or by manually drawing the outline (Fig.7). The basic design rules, such as default track sizes and minimum track/ pad clearances, can also be defined at this point. This done, the Design Synchronizer is invoked (from the Schematic Editor) to load and place all components onto the PCB layout. Initially, these appear outside the board outline, ready for manual or automatic placement. At this point, all component connections are shown in an aptly named “rat’s nest” configuration – see Fig.8. As each connection is made on the PCB, the associated rat’s nest connection disappears, making it easy to keep track of work yet to be done. Protel 99 includes a host of automatic component placement and routing tools that cater from the simple through to the most complex of designs. Naturally, the designer can also manually place part (or all) of the design if required. The designer can also define sets of rules to be adhered to during the layout process. Rules in over 25 classes such as component placement, clearances, net impedance and routing topology can be defined and enforced automatically in real-time, even during manual track routing (Fig.9). The familiar click-and-drag concept is used for manually placing and editing tracks. In addition, objects can be globally edited, making board-wide design changes a snap. Panning at higher zoom levels has been made easier too, using a new fea- Fig.6: selecting Design, Update PCB from the main menu displays the Design Synchronizer options. ture called “Slider Hand”. By clicking and holding the right mouse button, the PCB layout can be positioned smoothly beneath the viewing window. In practice, this is quicker and more accurate than using the scroll bars or shortcut keys. Gridless routing Protel 99 supports grid-based routing but gridless routing is also possible with a little help from Protel’s electrical grid and rules-driven design methodology. The electrical grid is an invisible grid that snaps the cursor to valid electrical connection points, regardless of the current routing grid setting. This is especially useful when working with a mixture of Imperial and metric-pinned components, for example. When working in tight spots, designers can place tracks without regard to their spacing and Protel 99 will automatically enforce minimum Fig.7: running the board Wizard to define the board outline and other basic design information. Starting the layout The first step in any PCB layout is to define the board outline. This January 2000  7 pleted, the final step is to generate the necessary output files so that the board can be manufactured. Several output files are involved and these are used to: (1) plot each layer photographically; (2) provide hole size and position information for a numerically-controlled drilling machine; and (3) provide component type and position information for mechanised assembly, if required. Protel 99 generates all of these files in industry-standard formats that should be acceptable by all PCB manufacturers. It also supports all Windows-based printing and plotting devices. Compatibility Fig.8: after creating the board outline and running the Design Synchronizer (see text), all components appear outside the board outline connected in a “rat’s nest” configuration. clearance rules. It can also move existing tracks to make way for new ones (Fig.10). Once completed, PCB layouts can be subjected to detailed design rule checking. These would generally be more comprehensive than the “online” checking done during placement and routing. As well as generating a detailed report, the Design Rules Fig.9: on-line design rule checking flags problems as they occur. In this example, the designer is routing a track that will exceed the minimum clearance rules to neighbouring tracks and pads and these are flagged by being highlighted in green. 8  Silicon Chip Checker can highlight any problems detected directly on the board (Fig.11). For high-speed digital design there is Protel 99’s Signal Integrity Analyzer. This feature can be run as part of the design rule check and provides crosstalk, reflection, impedance and other related analyses. Any problems can be further analysed and resolved with the help of the Signal Integrity Simulator. Once the PCB layout has been com- Protel 98 and Protel V3 files can be imported directly into Protel 99. However, if you need to import and edit files from earlier products than these, you might run into problems. For example, although Protel 99 will read PCB files created using Protel DOS products, it is not possible to directly import the associated libraries. If you do need to import older files like these, talk to the Protel support people – they will either do the conversions for you or provide the necessary tools for you to do the job. In summary, Protel 99 can import the following file formats: Netlist (Protel & Protel 2 format), Autotrax, DOS PCB 3, Protel PCB 2.8 (ASCII & binary), Gerber, AutoCAD DXF/DWG and OrCAD V7.x DSN. The following file formats can be exported: Netlist Fig.10: Protel 99’s “Avoid Obstacle” mode automatically moves existing tracks to make room for new ones in real time. The diagram at left shows the existing drawing, while the diagram at right shows how the centre track automatically moves when a new track is added immediately below it. This is a great time saver since you don’t have to manually move tracks out of the way. Fig.11: setting up the PCB Design Rules Checker. Where To Buy Protel 99 Protel 99 is available from Protel International Ltd, PO Box 1876 Dee Why, NSW 2099. Phone (02) 9984 0016; email sales<at>protel.com.au Alternatively, you can order a licensed copy on-line from the Protel website at www.protel.com.au A 30-day trial version is also available. In addition, Protel has announced that Protel 99 SE (second edition) will be available from January 2000 with even more features. (Protel format), Protel PCB 2.8 (ASCII), AutoCAD DXF/DWG and HyperLynx. Major new features Compared to earlier versions, Protel 99 also offers a number of important new features, particularly in the areas of multi-user support and document management. For example, all documents related to a project are now stored in a single design database. This even includes non-Protel documents like spreadsheets, AutoCAD drawings, etc. Multiple users can access these design databases simultaneously (without overwriting each Fig.12: using 3D PCB Viewer to display a board as it will look when assembled. It can be rotated to see it at any angle. This is a free plug-in that can be downloaded from Protel’s website. other’s work) and access rights can be assigned to each database on a per-user basis. A core program called Design Explorer brings all these elements together under a common interface. This program looks something like the familiar Windows Explorer and works in a similar manner. Using Design Explorer, you can open, navigate and organise your Protel databases (Fig.13). Multiple documents can be opened and viewed together and windows can be split into regions for side-by-side display. Protel has used a lot of the Windows Explorer shortcuts, so driving it all is quite easy. Add-ons Because it uses what Protel calls “open, client-server architecture”, a range of useful add-ons can be “plugged” into Protel 99. A good example of an add-on is the 3D PCB Viewer. As the name suggests, 3D Viewer generates an image of how the board will look when it is assembled. You can even rotate the board and view it in 3D from different angles – very impressive! The 3D PCB Viewer and a number of other useful add-ons can be downloaded free from Protel’s web site. Getting Help Fig.13: the Design Explorer looks like Windows Explorer and works in a similar manner. It lets you open, navigate and organise your Protel databases Protel 99 has a comprehensive online help system. If you can’t find the answer there, their web site is also a valuable source of help. It includes a searchable knowledge base, FAQ and updates download area. Check it out at http://www.protel.com.au In conclusion, we were very impressed with Protel 99. It’s a mammoth program that must have taken a huge number of man-hours to produce and it really does provide a comprehensive approach to electronic circuit design. To get more information, check out Protel’s free 30-day trial offer (see SC panel). January 2000  9