Requirement Description: Candence basic knowledge
Content: From schematic to PCB specific steps
from: time of the poem
From: Http://blog.163.com/tracy_zhangblog/blog/static/1938540202011117103433500/
A. Schematic diagram
1. Establish Engineering
As with other drawing software, OrCAD manages various design files with project. Click the Start menu, then all Programs-Allegro SPB 15.5--design Entry CIS, select the first item orcad_capture_cis_option with in the pop-up Studio Suite selection dialog box Capture, click OK to enter capture CIS. Next is File--new--project, in the popup dialog box fill in the project name, the path and so on, click OK to enter the design interface.
2. Drawing schematic diagram
The default schematic file opens after the new project SCHEMATIC1 PAGE1, with toolbars on the right, for placing components, drawing lines, adding networks, and so on, similar to Protel. Click on the Project Manager (folder tree icon) on the upper toolbar to enter the project management interface, where you can modify the schematic file name, set principle sheet size and add principle library, and so on.
1) Modify the schematic sheet size:
Double-click SCHEMATIC1 folder, right click PAGE1, select Schematic1 page Properties, in page size can select units, size, etc.;
2) Add principle Gallery:
File--new--library, you can see in the Library folder more than a LIBRARY1.OLB schematic library file, right-click the file, select Save, renamed to disk;
3) Add a new component:
Commonly used components with their own (such as resistors, capacitors), many times you have to do their own components, or use others to do the components. Right-click on the newly created OLB library file, select New part, or new part from Spreadsheet, which creates a new component in tabular form, which is suitable for chip elements with a lot of pin-out and can be directly copied from the PIN description table in the chip datasheet. , paste can (in PDF format datasheet ALT key can be selected by column), you can add pins in bulk, convenient and quick.
4) Generate a network table (NET list):
When you need to import a network table in the artboard, the schematic should be almost finished, and the rest of the job is to check for gaps. You can automatically number components, select the. dsn file under the project management interface, and then choose Tools--annotate, select some number sequences in the popup dialog box, modify them as required, or use the default settings. DRC detection is also an important task before generating a network table, which avoids some unnecessary design errors. After the DRC can try to build a network table, or in the project management interface, choose Tools--create netlist, you can select the network table in the Pop-up dialog box, the other default settings, the process of generating a network table if there is an error, Can pass windows--session log to see the cause of the error, for example, there are components forgot to add the package and so on.
5) Update the component to schematic diagram:
When a component in a library has been modified to require a schematic to be updated simultaneously, it is not necessary to reposition the component (in case there are 100 or more of the component is not going crazy), under the project management interface, double-click the Design Cache folder, select the component that you just modified, right-click Select Update Cache , go all the way to update the component in the schematic diagram.
6) Some details:
The magnification and reduction of the drawing schematic is the difference between the button "I" (zoom in) and the "O" (Zoom Out) and the Protel, in the creation of the component package, in addition to GND can have the same name, no other pin, no error, but seemingly error has no effect, Because the OrCAD comes with a library of components (such as Xilinx's FPGA), there is a pin with the same name except GND, and the shortcut key to add the network designator is "n", but the network designator cannot be copied in OrCAD. Remember that you can add a new network designator by copying the existing network designator in Protel.
two. PCB
1. Building a circuit boardThe first is to open the PCB editor-start-All Programs-Allegro SPB 15.5--PCB editor, select Allegro PCB design 610 (PCB design Expert) in the pop-up dialog, then click OK to enter the PCB editor. The next step is to use the wizard to build the circuit board, including determining the size of the board, the number of layers, shapes and so on, with the wizard more convenient. Click the File menu, select New,
Pop-up dialog box drawing type Select Board (Wizard), then determine the file name, save path, etc., last click OK to enter the wizard. In the import data this step can go all the way next, with the default parameters on the line. To parameters, you can first select the units used in the artboard (select the units for Board drawing), that is, with a mil, MM or other, according to personal habits, the general choice of Mil; next, select the paper size (drawing Size, note that it is not a board); the third option is to select the coordinate origin of the sheet (in the lower left or center, then change it), and you can select the center as the origin of the coordinates, depending on your needs. Click Next when you're done, and then set up other parameters. Set the grid point size (grid spacing) to 10mil, set the number of route layers (Etch layer count) to 2 (2 layers), and then go all the way next until the spacing Constraints (distance parameter limit) of custom data. Here you set the minimum width (Minimum line width), Minimum line spacing (Minimum lines to line spacing), route to pad minimum spacing (Minimum line to pad spacing) and the minimum pad spacing (Minimum pad to pad spacing) are 8.00mil,default via Padstack Select Via, then click Next. At this time choose the form of PCB rectangular board (rectangular), click Next into the rectangular PCB parameter setting interface, the main setting is the board width (width) and height (height) and some restricted areas, Including the distance between the allowable area of the wiring and the board frame, and the distance between the allowed component area and the board border (can be set to 50 and 100mil respectively), after the completion of the next, the final point finish, this step is accomplished.
2. Import a network tableNext step, import the network table into the newly built PCB. Before this, there is a very important work to do, is to specify the path of the PCB package. Remember that when drawing a schematic diagram, just filling in the component's package name in the element attribute, and not telling the Allegro component where the PCB is encapsulated, without specifying the package path, the import of the network table will be an error. Click Setup--user Preferences, select Design_paths in the Pop-up dialog categories, and specify the path for Padpath and Psmpath, respectively. Add the PCB component package path to Padpath and Psmpath to tell Allegro to look for encapsulation from the path you specify. One of Allegro's PCB component packages will contain several files (some of which are necessary for network tables, some are not), and unlike Protel, a PCB library file can contain many component packages. How to get the components of the PCB package, the old-fashioned way, do it yourself or directly with others do. There is a man for Allegro specifically made a PCB package generator--fpm (Footprint Maker, the current version is 0.0.8.0), can generate a large number of commonly used PCB package, very useful (really benefit the brothers on the road feat). Use FPM to select the package you need, make it, the package will do it automatically, and then automatically open the finished package with Allegro to check that the resulting package is right. Package ready, you can start to import the network table into the PCB, click File--import--logic, specify the network table file path generated in the schematic section in import directory, other settings use the default values, click Import Cadence can import network tables. If the import fails, you can see the cause of the error through the log file, correct the error and repeat the process until the network table is successfully imported.
3. Placing ComponentsAfter you successfully import the network tables, you can start placing the components. Click the menu place--quickplace, use the default settings in the popup dialog, and click the Place button to complete the placement of the component. If you encounter a component that has not been successfully placed, a component count that is not successfully placed will appear above the place button, as in the form: Unplace symbol COUNT:4. Click on the viewlog on the right to see if those components have not been successfully placed. For example, the lack of pads in the PCB component package will result in placement failure, which can be re-placed once the package has been modified.
4. LayoutNow can be based on the actual demand on the PCB display components, at this time the components are basically placed on the outside of the board, and there are dense lines of flying (rats). In order to better put the components, you can temporarily remove the fly line, by clicking the Unrats All button in the toolbar, the method of recovery is the right side of the rats all button. To move a component, you must first click the Move button in the toolbar or use Shift+f7 to go to the "move" command mode, tick symbols in the Find tab in the Control Panel on the right side of the interface, then click the component you want to move, move the mouse (the component moves with the mouse) to the new position, Click the mouse button again to complete the placement. While still in the Move command mode, the same method can be moved directly to other components, press F2 or the right-click menu done can exit the Move command mode (back to idle mode). The rotation of the components is interesting, when moving the components, right-click the rotate, the component center and the mouse pointer pull out a line, with the mouse pointer to the center of the component circle, the components follow the beginning of rotation, go to the right position by clicking the mouse to determine the direction of placement. The layout of the time can be directly from the schematic location of a component directly, because the beginning of the components are stacked in a piece, that is, set schematic to PCB interaction. By selecting the menu options--references in the OrCAD Capture CIS, select Enable Intertool Communication under the Miscellaneous tab. When a component is selected in the schematic, it will be directly positioned on the PCB (must be in idle mode). Sometimes you need to put a component on the bottom, by tapping the menu edit--mirror, entering the command mode, and then clicking on the component you want to put on the back.
5. CablingIt's not customary to use Allegro for the first time (probably because of the habit of Protel), such as zooming in and out of the PCB shortcut keys, not pageup and PageDown, but F10 and F11. Again, such as in the Protel mobile PCB drawing can be used with the mouse wheel (move up or down) or shift with the mouse wheel (move left and right), or the mouse button or the middle button press and hold can also, in Allegro, just hold down the middle mouse button or use the arrow keys. Of course, these can be changed by the relevant settings to their own habits of the way, "cadence system is a relatively open system, it gives users a lot more custom space." There is a more unaccustomed place is the color of the setting, because the default settings are too bad, must be changed to see (otherwise it will crash). Click the Color button in the toolbar or the Ctrl+f5 or menu display--color/visibility, and in the popup dialog you can see that Allegro has set the color settings in several group settings, respectively, according to personal habits, such as stack-up , you can set top (top level) or bottom (top) pin (Pins), Via (through Hole) and etch (route) to red and blue (default color settings in Protel), Geometry set skillscreen_top (top screen) to yellow , the color of the column of ref Des (symbol) set skillscreen_top in Components is yellow. After a set up, to feel more friendly, start wiring ... You can change the line width at any time in the right control Panel by tapping the menu route--connect or the shortcut key F6. Add via command on the right-click menu at any time, allowing the cabling to travel between the top and bottom layers. There is also an unaccustomed place, the pads (with holes) and vias are solid (how can be called "hole"), in order to be "hole", click on the menu setup--drawing options under the Display label, select the display plated holes can be. Wiring when automatically push the wiring, very good, in addition, you can set some rules according to the requirements of constraints, click setup--
Constrains, click the Set standard Value button in the Pop-up dialog box to set the pad spacing, line width, and other parameters.
6. Plate makingThe board is to provide PCB manufacturers with Gerber files to wash out the board (similar to the washing of photos, Gerber files similar to the film). Before out of the Gerber must also do some necessary testing work, such as the package is not wrong (main check object), there is no connection network and so on ... If you do not test carefully, then you will probably want to cry without tears. found that the PCB package is wrong, modified, and then updated in the PCB modified package, Place--update Symbols, in the package Symbols to select the packaging needs to be updated, choose after the update symbol Padstacks, Finally, click Refresh. If you open the on-line DRC (which is open by default in rule constraints), you also need to pay special attention to where the DRC appears, and change it if necessary. All right after the PCB can be paved with copper, before the laying of copper parameters can be set, click the menu Shape--global dynamic Params, in the Shape Fill tab, the Dynamic Fill option to select smooth Smooth fill, Open the Void Controls tab, artwork format select Gerber rs274x. Then, click on the menu shape--rectangular (auxiliary rectangle), at this time you can set the layer of copper in the right Control Panel option, and select the corresponding network of copper laying, remember to delete the copper laying dead zone, Shape--delete Islands. At this point, the work of the artboard is finished, can be out of Gerber. Click Manufature--artwork, open in the Pop-up dialog box
General parameters label, Device type Select Gerber Rs274x,format in the Integer places:3,decimal places:5, and then open the film Control label, Add to complete the required film, the general two-layer board will need top (top layer), BOTTOM (bottom line layer), soldermask_top (top layer solder layer), soldermask_bottom (bottom solder layer),
Skill_top (top layer screen printing) and skill_bottom (bottom screen), add the required negative file, set undefine line width of 8 (do not know why this value), the other settings use the default value, and finally click Create artwork, You can also view related records when the Gerber file is generated by using the Viewlog button
Candence Basics 1 (cadence from schematic to PCB steps)
