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INTRODUCTION DESCRIPTION CIRCAD is a menu-driven printed circuit design and editing program. It is a very easy program to learn, because nearly all the information needed to operate the program can be accessed through pull-down and pop-up menus. CIRCAD allows you to lay out circuit boards in great detail without the arbitrary restrictions found in most CAD packages, and without the tedium and bother of tape and decals. The ultimate product of CIRCAD is data files that will directly drive a Gerber photoplotter in producing the artwork for a finished board. In addition, CIRCAD can drive pen plotters, produce drill plots and parts lists, and import/export data from a number of other CAD packages. Also, if a compatible netlist is used, CIRCAD can fully autoroute a digital circuit board, or check tracks against nets on any board. CIRCAD is for both the novice and the experienced CAD user. The first-time CAD user will find the manual invaluable in becoming familiar with CIRCAD, while the experienced user will probably jump right into the program, only occasionally referring to the manual. System Requirements To use CIRCAD, you will need the following minimum hardware and software systems: IBM PC-AT computer (or compatible clone). CIRCAD uses only integer arithmetic instructions. As a result, no decrease in performance will be observed if you do not install a numeric co-processor. However, a fast data bus with a 16-bit video display card is highly desirable, since CIRCAD places a very heavy util-ization load on the bus and the video sub-system. DOS version 3.1 (or greater). CIRCAD uses functions calls that are not avail-able in versions 2.xx of DOS. Video Graphics Array (VGA) display controller. CIRCAD was designed specific-ally for use with the VGA display controller. If your machine is equipped with an EGA display controller, a scaled-down software driver is provided with fea- tures similar to that of the VGA driver, but at a reduced resolu- tion. High Resolution Color Monitor. A color monitor is recommended to effectively display the various layers of the circuit board. A grey-scale monochrome unit is only marginally useful for this purpose. Mouse and Mouse Driver. CIRCAD requires a resident mouse driver attached to interrupt request vector 33(hex). This means that the software that came with the mouse MUST be installed. Although the arrow functions of the keyboard's ten-key pad are essential for finely detailed work with small grid snap settings, general operation without a mouse is very tedious for the large-scale cursor movements needed to process the assorted pull-down and pop-up service menus. Pen Plotter. A graphics plotter is almost essential. A low-cost unit such as a Hewlett-Packard 7475 will be adequate for most applications. However, any plotter supporting HPGL or DMPL plotting languages be used. ON-LINE HELP On-line help is available at any time by pressing the <center mouse> button or <Alt-F10> on the keyboard. CIRCAD's help func- tion is both interactive and con-text sensitive, providing instant access to information about whatever CIRCAD feature is currently in use, without a lot of searching and guessing at key-words. FILE BACKUP Each time you exit from CIRCAD, the program will display, in sequence, each of the files you have modified, with the warning: "File has been updated but has not yet been saved. Save file before exit?" Simply selecting "No" leaves the file as it was when the session began. Selecting "Yes" saves your changes to disk. CIRCAD also contains an automatic file backup feature. If, at the end of a session, you elect to save the changes you've made to a file, CIRCAD does so -- but first it stores the old version in a subdirectory called "BACKUP". If no backup directory is available, a backup copy of the file is created in the same direc- tory by changing the filename suffix to ".BAK". This enables you to recover quickly should you unintentionally save undesirable changes to one of your files. To keep your hard drive from quickly filling up with outdated files, CIRCAD keeps only one previous version of each file in the BACKUP subdirectory. FILE IMPORT/EXPORT FILTERS CIRCAD has the ability to automatically read (import) files that were created using other circuit board design programs, and can also write out (export) files compatible with those programs. CIRCAD can import files from Orcad(PCB), Autotrax(TRAXEDIT), Tango(EDIT), Tango(PCB), and AutoCad(DXF). In addition, it can import Gerber, HPGL, and DMPL plot files. AUTOPANNING Screen autopanning is a very useful CIRCAD feature. When CIRCAD is first installed, however, autopanning is turned off. Auto- panning is controlled by invoking the "Setup: Draw Modes" menu. TUTORIAL From concept to schematic to printed circuit board. The typical circuit starts out as an idea which gets jotted down on a dinner napkin at the cafeteria. Once back from lunch, the basic idea is soon converted into an approximate schematic on a real sheet of paper. After the circuit has won preliminary apro- val, it is necessary to transfer the information to the computer at which time the schematic must be refined and filled out to its final configuration. The computerized schematic can then be used to generate much of the data that is needed to build the finished printed circuit board. CIRCAD is designed to make this process as straightforward as possible by providing an unbroken pathway from schematic to printed circuit board to check-plot to final photo plotting and assembly drawings, all in a single integrated program. The following tutorial will walk you through the process, from schematic to finished board design. CAM output functions (pen/laser plots, Gerber files, etc.) are covered in detail in their own chapters. SCHEMATICS Because CIRCAD is able to hold more than one file open at a time, you can start a new file at any time. Just invoke the main menu bar (press <space bar> or roll the cursor to the top of the screen and press <Enter> or <left mouse>) and click on the selection `File'. As a shortcut, you could simply type <F> to make the main menu bar and the File menu appear simultaneously. Select `New File' by clicking on it, and a pop-up dialog box will ask you to name your new file. Assigning schematic files a suffix of `.SCH' is a useful convention for easy identification; if your schematic will have more than one sheet, the suffixes `.SH1', `.SH2', etc. should be used (note that you can use the `Save As' function to rename any file at a later date). When you have typed in the file name and pressed <Enter>, another pop-up dialog box will ask you to select a template. Since CIRCAD can work with many different file types and sizes, a large number of setup parameters are needed to establish the proper working environment for a given data set. The template system is provided as a mechanism for both saving time and reducing errors. The basic set of templates can be easily customized later when your familiarity with the program increases. For now, simply select the template for the desired size of the schematic you plan to create, and you will see the empty drawing sheet appear at maximum magnification. Use the `Place Text', `Edit Text' and `Delete Text' functions as necessary to enter the necessary data into the title block in the lower right-hand corner of the drawing sheet. Now you are ready to begin entering your schematic. PLACING PARTS FROM THE SOURCE LIBRARIES You'll want to start by placing the required components. Select `Place' and then `Component' from the main menu, and a pop-up dialog box will appear, asking you to enter the component parameters: `Pattern', `Ref ID', `Type/value', and `Modifier'. If you know the pattern name of the part you wish to place, you can type this in directly and press <Enter> to move on to the `Ref ID' field. However, you may prefer to browse one of CIRCAD's source libraries to select the part you need. To do this, simply type <?> and <Enter>. Another pop-up menu box will then ask you to select the desired library. You can have up to 16 libraries per data file. Once you have selected one of the libraries, you will see that the individual components are arranged by function for easy selection. You may use the Page Up/Down buttons at the right of the menu to scroll through the library. When you have found the part you want, you may select it by pressing <Enter> or <left mouse>. CIRCAD then returns to the com- ponent parameters dialog box, having automatically filled in all the data fields provided for in the library component. You may use the `Modifier' field to include additional information about the component as required. Note that CIRCAD has automatically assigned a `Ref ID' to this particular component. CIRCAD will continue to assign sequential `Ref IDs' as you place each component. In the case of multi-section chips (such as AND gates and flip-flops), CIRCAD will keep track of which chips already on the schematic have open sections available, and will assign subsequent components to those open sections using suffixes `b', `c' and so on. If no open sections are available, CIRCAD will assign the part a new number with the suffix `a'. After you have entered the `Modifier' (if any), all dialog boxes disappear and you will see the `ghost' of the part attached to the cursor. When you have properly positioned the component, press <Enter> or <left mouse> to place it. Place the remainder of the of the parts in a similar fashion. A special note on TTL and CMOS parts: CIRCAD assigns power and ground automatically to these parts through special `hidden' pins at the top and bottom of each symbol. These power and ground pins carry the signal names VCC and GND for TTL parts, and VDD and VSS for CMOS parts. All VCC pins on a given schematic will automati- cally be placed into the signal net list. The same holds true for GND, VDD and VSS pins. PLACING PARTS FROM THE IMAGE LIBRARY No set of generic libraries could possibly include the huge variety of connectors and other special components that designers sometimes require. For this reason, a second type of library is available for `storage' of special components that you yourself may create on an as-needed basis. This library is an image library, showing drawings of the parts rather than listing them by pattern number. The image library is easy to access: When you invoke the `Place Component' command and the `Component Placement' dialog box appears, simply clear all characters from the `Pattern' field and press <Enter> or <left mouse>. The image library will immediately be called up on screen. Note that the cursor remains an arrow rather than a cross-hair, indicating that you are in `view' mode only -- the components in the library cannot be manipulated in this mode. In fact, if you invoke the main menu bar, you will see that only the `Zoom' func- tions are enabled. To select one of the parts shown, simply place the arrow cursor on it and press <Enter> or <left mouse>. A pop-up dialog box will appear, showing the parameters of the selected part. You may then either `Confirm' your selection or `Escape' to select a different part. If you confirm the selection, you are returned to your schematic file and the `Component Placement' dialog box where you will be prompted to enter the particulars of this individual component. Note that you must select and enter your own `Ref ID' for these customized parts. From this point on, component placement is identical to the procedure outlined in the previous section for the standard libraries. To create components and add them to the library, follow the pro- cedure outlined in Chapter 11. PLACING SIGNALS CIRCAD offers several different types of element for connecting the various components on the schematic. All of these are available under the `Place' command on the main menu bar. SIGNAL WIRE. The simplest of all elements, signal wires are used to connect two or more component pins together. Signal wires which cross are not seen as electrically connected unless their junction is marked by a signal dot. SIGNAL DOT. Signal dots are used to join two signal wires together. SIGNAL NAME. Used to attach a name to a signal wire. BUS WIRE. This is used to place a thick bus line, to which many signals can be attached through bus ports. SIGNAL PORT. A signal port allows you to run a given signal to many different pins throughout the schematic, without actually drawing a trace to connect them all. When you select the command `Place: Signal Port', CIRCAD asks you to give the signal a name. When you place the signal port, a tag appears with that signal name on it. You can place any number of signal ports with the same name; all signal ports to which you assign that same name are seen by CIRCAD as electrically connected, i.e., as a single net. BUS PORT. These are the entry or exit points on a bus to which individual signals are attached. The identity of each signal is specified by a signal name parameter. + PWR PORT, - PWR PORT, GND PORT. Similar in operation to signal ports, these ports allow you to connect power and ground as required, without cluttering the sche- matic with traces. The procedure for moving and deleting any of the signal ports is similar to the procedure used for components. NETLISTS AND BILLS of MATERIAL. If you want to end up with a good printed circuit board, you must start with a good schematic. You may print or plot your schematic as often as necessary to make sure it is exactly what you want -- now is the time to iron out any snags, before you proceed to the final step. The next step in the process is to use your finished schematic data file to generate a bill of materials (BOM) and a netlist. With a BOM, you can have a ready reference for placing components on the bare board; with a netlist, you can `ratsnest' all the nets on the PCB to optimize component placement and facilitate manual routing. A netlist also gives you the option of autorouting the board. To generate a BOM, select `File' and `BOM Output' from the main menu. CIRCAD will ask you to assign a path and file name to this BOM; the default name is the name of your schematic file with the suffix `.BOM'. Since the file is a straight ASCII file, it can be called up, edited and printed by any standard line editing program. You can also send the .BOM file out to a printer via a parallel port without leaving CIRCAD. Just erase the entire path and file name shown on screen and type in `LPT1' or `LPT2' to correspond to your printer connection. Two sheets will be printed. One will list all components in the order of their `Ref ID', indicating their position on the schema- tic, pattern, value, and modifier. The other sheet will list all components by part type/value, indicating the quantity for each part and a spread sheet of the `Ref IDs'. To generate a netlist, select `Nets' and `Netlist Out' from the main menu. As with the BOM, CIRCAD will prompt you to enter a path and filename, offering your schematic file name with the suf- fix `.NET' as a default. Again, the `.NET' file is a straight ASCII file which can be called up, edited and printed using any standard line editing program. Or you can print it off from CIRCAD by typing in the device name `LPT1' or `LPT2'. CIRCUIT BOARDS Next, create a new PCB file. As with the schematic, select `File' and `New File' from the main menu bar. Name the new file with a `.PCB' suffix, select the proper template, and you're ready to create the board. Use the `Place Line', `Place Arc', etc. commands to draw the outline of the board (on the pad master layer) and any other details such as dimensions or miscellaneous boilerplate text. Now you can place all the components. As with the schematic, selecting `Place Component' from the main menu calls up a dialog box asking you to enter the component para- meters. You can take these right from the bill of materials. Again, as with the schematic, you can browse the libraries if you prefer. If you type in <?> for the pattern and press <Enter> or <left mouse>, you will see the available libraries: `THD.LIB' for through-hole devices and `SMD.LIB' for surface-mount devices. Select the appropriate library and you will see a listing, by function, of the components available. An image library is also available which shows drawings of a variety of standard packages, and which serves as a `storage' place for any components you may create yourself from time to time. Access it by clearing the `Pattern' field of the `Component Parameter' dialog box and clicking on the blank space. You can then view the image library and select PCB components in the same manner described for selecting schematic components. Building your own components and adding them to the library is described in detail in Chapter 11. After you have placed all the parts listed on the bill of materials, you're ready to move on to netlists. NETLISTS Importing the netlist to your new PCB file is easy: Select `Nets' and `Netlist In' from the main menu, and CIRCAD will ask you to specify the name of the netlist. The default will be the name of the current file with the suffix `.NET'. Once the file name is entered, the netlist will immediately be read into the PCB file. Note that if any components are missing from the board, CIRCAD will alert you with a beep and a message on the status line. Use the netlist first to place the components logically on the board. Select `Nets' and `Ratsnest' to connect all nets with straight lines, and use trial and error to place the components to minimize congestion and crossing. When you are satisfied with the component placement, you are ready to route the board. Use your usual method to route the board manually, or refer to Chapter 8 for detailed instructions on using CIRCAD's autorouter. Plotting the circuit board and generating Gerber output are covered in detail in Chapters 9 and 10. COMMAND REFERENCE This chapter contains a brief description of the CIRCAD menu selection system. There is one section on each of the pull-down menus of the main menu bar. Each section begins with some general information about the menu as a whole, followed by a subsection on each menu item. The main menu bar may be invoked by using any of the three following methods: 1. Press <space bar> on the main keyboard. 2. Type a key that matches one of the nine "action" characters that are highlighted on the main menu bar. 3. Slide the cursor up to the top scan line of the screen and press <left mouse> or <Enter>. Once invoked, the cursor can be easily moved about the menu selec- tions by either using the left, right, up, and down arrow keys on the keyboard's ten-key pad, or by rolling the mouse about. As each menu is displayed, a prompting message for that menu is pro- vided on the status line at the bottom of the screen. THE FILE MENU The selections in this menu are used to control the flow of data into or out of the active system memory. New File. This selection is used to begin a new drawing file that does not currently exist on disk. A pop-up dialogue box will appear for the entry of the disk file name followed by a second dialogue box for the entry of a tem-plate file that will be used to establish the basic working parameters for the new data file. Open File. This selection is used to view or edit a data file that already exists on disk. A pop-up dialogue box will appear for the selec- tion of the desired data file. Opening a file that is currently active in the system is not allowed. Close File. This selection is used to remove a data file from the active system memory, thus freeing its space for use by other files. If the file has been modified since the most recent save operation, a pop-up dialogue box will appear and you will be prompted to indi- cate whether you want to save the current file to disk, discard the changes, or escape from the requested function. Next File. This selection is used to switch the display and editing system to the next sequential element in the set of active data files. The files are accessed in a rotary fashion in the order in which they were opened. Prev File. This selection is used to switch the display and editing system to the previous sequential element in the set of active data files. The files are accessed in a rotary fashion in the reverse of the order in which they were opened. Information. This selection is used to display statistical information on the current data file. Save File. This selection is used to write the current data file out to disk. You should use this function periodically during a session to help protect your work from loss due to power outages, etc. The first time a file is saved, the file name extension on disk of the opened file is changed to ".BAK" for backup purposes. Any previous ".BAK" file is overwritten. As an alternative file backup mechanism, if a directory exists on the specified drive with the name "\CIRCAD\BACKUP", the original file is moved to that directory without changing the file name extension. Save As ... This selection is used to write the current data file out to disk under a different name or format. A pop-up dialogue box will appear for the entry of the new disk file name. You may use this function to create multiple copies of the same data file, since one file will not overwrite another if you specify a unique file name for each separate copy. If the newly entered file name already exists on disk, a pop-up dialogue box will appear and you will be prompted to indicate whether you want to overwrite the previous data file, enter a new file name, or escape from the requested function. Gerber Output. This selection is used to create a set of data files on disk in RS-274-D format for subsequent plotting by a Gerber photo plotter. A pop-up dialogue box will appear for the specification of the desired output data files. Plotter Output. This selection is used to create a hard copy of the current data file on a graphics printer or ink pen plotter. A pop-up dialogue box will appear for the selection of the layers to be plotted and the conditions under which the plot will occur. BOM Output. This selection is used to write out a bill of materials and parts listing from the current data file to disk in the form of a prin- table ASCII data file. A pop-up dialogue box will appear for the entry of the desired destination file name. Entering "LPT1" or "LPT2" will send the reports directly to the printer. Library View. This selection is used to view or edit the current symbols library data file. If no library file has been opened, a pop-up dialogue box will appear for the entry of the desired library file name. Library File. This selection is used to open a new symbols library data file. A pop-up dialogue box will appear for the entry of the desired library file name. Script File. This selection is used to load and execute a command file from disk. A pop-up dialogue box will appear for the entry of the desired script file name. This function is useful to effect large-scale changes in the function or operation of CIRCAD during a editing session. Help Index. This selection may be used to access the help messages in an interactive mode. The preferred (context sensitive) method is to press <center mouse> or <Alt-F10>. Exit/Quit. This selection is used to end an editing session and return to the operating system. If you have modified any of the active data files, a pop-up dialogue box will appear for each such file and you will be prompted to indicate whether you want to save the file to disk, discard the changes, or escape from the requested func- tion. THE PLACE MENU The selections in this menu are used to add new elements to the current data file. Most of the selections invoke a pop-up dialo- gue box for detailed specifications on the element to be placed. Each of the selections sets the specified function to be repeated automatically whenever <left mouse> or <Enter> is pressed. Once set in this manner, the function remains in effect until it is reset by a different menu selection. Place Line. This selection is used to draw a straight line segment between two points. A pop-up dialogue box will appear for the entry of the destination layer and line thickness. Place Ortho-line. This selection is used to draw a straight line segment that is constrained to follow one of the four cardinal directions and their four diagonals. A pop-up dialogue box will appear for the entry of the destination layer and line thickness. Place Vertex. This selection is used to add a vertex to the interior of an existing line segment. This function is useful as an alternative to deleting the old line and placing a new one when routing around an obstacle. Place Arc/circle. This selection is used to create a partial or complete circle or ellipse. A pop-up dialogue box will appear for the entry of the destination layer, line thickness, major radius, start angle, sub- tended angle, elliptical eccentricity, and rotational angle. Place Pad. This selection is used to create a pad, a via, or a mounting hole. A pop-up dialogue box will appear for the entry of the destination layer, pad type, pad size, hole size, and pin number. Place Via. This selection is used to place a via. The default parameters used to create the via may be modified under the "Setup" menu. Place Text. This selection is used to create an alphabetic text string. A pop-up dialogue box will appear for the entry of the destination layer, text size, and rotational angle. Place Component. This selection is used to fetch a component from the symbols library. A pop-up dialogue box will appear for the entry of the symbol pattern name, the component reference ID name, the part type or value, and a part descriptor. If the component pattern name is not known, entering a question mark [?] will invoke the symbols library in browse mode. Place Signal Port, Place Bus Port, Place + Pwr Port, Place - Pwr Port, Place GND Port. These selections are used to create a name tag for a signal wire. A pop-up dialog box will appear for the entry of the signal name. These functions are active on schematic data files only. Place Signal Name, Place Signal Dot, Place Signal Wire, Place Bus Wire. These selections are used to create place special-purpose lines, vias, and lines for schematic data files. THE GRAB MENU The selections in this menu are used to move existing elements to new locations. A file element so selected will be removed from the file and a "ghost" of the element will attached to the mobile graphics cursor and will travel about the file as the cursor is moved. In this ghost form, the grabbed file element can be rotated in 90 degree increments by pressing <R> and can be mirrored by pressing <X> or <Y>. The element can be returned to its original position in the file at any time by pressing <right mouse> or <Escape>. When the element has been properly reposi- tioned, it can be set back down onto the drawing field by pressing <left mouse> or <Enter>. No pop-up dialogue boxes are used by the grab functions. Each of the selections sets the specified func- tion to be repeated automatically whenever <left mouse> or <Enter> is pressed. Once set in this manner, the function remains in effect until it is reset by a different menu selection. Grab Line. This selection is used to pick up one entire line segment, along with any free pads, vias, and other vertices coincident with the line segment's end-points. Items contained within components are not accessible with this function. Grab Vertex. This selection is used to pick up the "tail" of a line segment, along with any free pads, vias, and other vertices coincident with that end-point. Items contained within components are not accessible with this function. Grab Arc/circle. This selection is used to pick up a single arc, circle, or ellipse. The cursor must be placed within the interior of the element. In the event of overlapping targets, items on the current layer are given preference over those on other layers, and items with smaller radii are given preference over those with larger radii. Items contained within components are not accessible with this function. Grab Pad/via. This selection is used to pick up a single free pad, via, or mounting hole. Items contained within components are not accessible with this function. Grab Text. This selection is used to pick up a single text string. In the event of overlapping targets, items on the current layer or items not owned by a component are given preference. Grab Component. This selection is used to pick up a component and all line segment vertices coincident with the component's signal pads. In the event of overlapping target components, smaller components are given preference over larger ones. Grab Comp Only. This selection is used to pick up a component leave while leaving the signal tracks behind. In the event of overlapping target com- ponents, smaller components are given preference over larger ones. Grab Item. This selection is both powerful and difficult to use. The current working layer must be correctly set and the cursor positioning must be absolutely accurate before this function can be used. Any of the primitive items can be grabbed and attached to the cursor, even if they are contained within a component. Pads and arcs must be grabbed from their central point, lines segments may be grabbed from any point along the mathematical center line, and line end- points must be grabbed from the exact end-point. Rotate 90 degrees. This selection may be used to rotate any grabbed cursor attach- ments. Mirror X. This selection may be used to flip any grabbed cursor attachments along the X axis for a reversed view. Mirror Y. This selection may be used to flip any grabbed cursor attachments along the Y axis for a reversed view. THE EDIT MENU The selections in this menu are used to modify the parametric values of existing file elements. Most of the functions invoke a pop-up dialogue box that lists the item's current parameters and allows for the modification of those parameters. Each of the selections sets the specified function to be repeated automati- cally whenever <left mouse> or the <Enter> is pressed. Once set in this manner, the function remains in effect until it is reset by a different menu selection. Edit Line. This selection is used to modify line segments by changing their thickness or by transferring them to different layer. A pop-up dialogue box will appear with the current parameters and the per- missible global editing options. Items contained within com- ponents are not accessible with this function. Edit Arc/circle. This selection is used to modify a partial or complete circle or ellipse. A pop-up dialogue box will appear with the current para- meters and the permissible global editing options. Items con- tained within components are not accessible with this function. Edit Pad/via. This selection is used to modify a pad, a via, or a mounting hole. A pop-up dialogue box will appear with the current parameters and the permissible global editing options. Edit Text data. This selection is used to modify the data portion of an alphabetic text string. The text is edited in place on the screen. Edit Text parms. This selection is used to modify the parametric portion of an alphabetic text string. A pop-up dialogue box will appear with the current parameters and the permissible global editing options. Edit Component. This selection is used to modify the parameters associated with a component. A pop-up dialogue box will appear with the current parameters. Locate Cmp. This selection is used to jump the cursor to the reference point of any component on the current data file. A pop-up dialogue box will appear for the entry of the desired component name. Krump Cmp. This selection is used to add items to a component, to remove items from a component, or to dissolve a component into its constituent parts. The item or component acted upon must be first be attached to the cursor by using one of the "Grab" functions. The operation of this function is smoothest when invoked through the keyboard by typing <EK>. THE DELETE MENU The selections in this menu are used to remove existing elements from a data file. All of the delete functions can be undone imme- diately by pressing <right mouse> or <Escape>. No pop-up dialogue boxes are used by the delete functions. Each of the selections sets the specified function to be repeated automatically whenever <left mouse> or <Enter> is pressed. Once set in this manner, the function remains in effect until it is reset by a different menu selection. Delete Line. This selection is used to remove a single line segment. In the event of overlapping targets, items on the current layer or items shorter in length are given preference. Items contained within components are not accessible with this function. Delete Multi-Line. This selection is used to remove an entire signal track. The target line segment is first deleted, then, recursively, each line segment, free pad, or via coincident with the deleted line segment's end-points. Items contained within components are not accessible with this function. Delete Vertex. This selection is used to remove a vertex from the interior of an existing multi-line signal track. Items contained within com- ponents are not accessible with this function. Delete Arc/circle. This selection is used to remove an existing arc, circle, or ellipse. Items contained within components are not accessible with this function. Delete Pad/via. This selection is used to remove a free pad, a via, or a mounting hole. Items contained within components are not accessible with this function. Delete Text. This selection is used to remove an alphabetic text string. Delete Component. This selection is used to remove an entire component. Any attached signal tracks will remain in place. Delete Grab/Hilite. This selection is used to delete any items that have been grabbed or that are highlighted. THE SETUP MENU The selections in this menu are used to modify the functional parameters of the data file or of the data base in general. All of the functions invoke a pop-up dialogue box that lists the current parameters and allows for the modification of those para- meters. Setup Layers. This selection is used to control all parameters specific to indi- vidual layers of the data file. Setup Draw Modes. This selection is used to control all parameters specific to the screen redraw functions. Setup Zoom Limits. This selection is used to contain the ultimate movement of the cursor within a restricted region of the total workspace size. Setup Grid Dots. This selection is used to set the spatial density of the background grid. Setup Grid Snaps. This selection is used to set the elements in the rotary grid snap table. Grid. This selection may be used to extract the next sequential value from the grid snap table. The values are accessed in a rotary fashion. Setup Via Params. This selection is used to set the default parameters used by the "Place Via" function. THE BLOCK MENU The selections in this menu are used to temporarily define a group of file elements and to perform transformational functions on all elements in the group. Several of the block sub-functions invoke pop-up dialogue boxes to display current parameters and to allow for the entry of new parameters. Block Define. This selection must be used to define a containment region before any of the other block functions may be used. Block Release. This selection may be used to un-define a containment region and thus disable block processing. Block Move. This selection is used to relocate the data file elements within a block containment region to a new position on the same data file. Block Copy. This selection is used to duplicate the data file elements within a block containment region to a new position on the same data file or in a different data file. Block Delete. This selection is used to remove all data file elements within a block containment region. Mirror X. This selection may be used to flip any defined containment block along the X axis for a reversed view. Mirror Y. This selection may be used to flip any defined containment block along the Y axis for a reversed view. Block Rotation. This selection is used to control the rotational translation para- meter to be used by the "Block Move" and "Block Copy" functions. A pop-up dialogue box will appear with the current rotational parameter and a new value may be entered. Block Scaling. This selection is used to control the magnification translation parameter to be used by the "Block Move" and "Block Copy" func- tions. A pop-up dialogue box will appear with the current magni- fication factor and a new value may be entered. Block Layers. This selection is used to control the block layer inclusion table to be used by the "Block Move", "Block Copy", and "Block Delete" functions. A pop-up dialogue box will appear with the current layer table and a new set may be entered. Block Build Comp. This selection is used to consolidate the free data file elements within a block containment region into a single entity known as a "component". THE NETS MENU The selections in this menu are used to process signals as a group known as nets. Netlist In. This selection is used to read in a netlist file from disk and add its routing information to the current data file. A pop-up dialo- gue box will appear for the entry of the desired source netlist file name. All existing signal names will be lost. Netlist Out. This selection is used to write out the routing information from the current data file to disk in the form of netlist. A pop-up dialogue box will appear for the entry of the desired destination netlist file name. Rats-nest. This selection is used to display the set of straight line connec- tions needed to complete the routing of a circuit board. Auto-route. This selection is used to convert a rats-nest of signals into an orderly set of signal tracks. Hilite Net. This selection may be used to illuminate all tracks, pads, and vias along a single signal path. Name Net. This selection may be used to assign a label to a highlighted signal net. Net Scan +. This selection is used to scan forward through the named signal nets searching for connection anomalies. Net Scan -. This selection is used to scan backward through the named signal nets searching for connection anomalies. THE ZOOM MENU The selections in this menu are used to change the view of the current data file without affecting the contents of the file. Zoom In [1.414x]. This selection is used to magnify the image of the data file, yielding a smaller field of view at a greater resolution. The ultimate limit of this function is reached when one pixel on the screen has a value of 0.001 inch. Zoom Out [.707x]. This selection is used to de-magnify the image of the data file, yielding a larger field of view at a lesser resolution. The ulti- mate limit of this function is reached when the file at the spe- cified zoom limits just fits on the display screen. Zoom Scale [1:1]. This selection is used to snap the zoom scaling to unity magnifi- cation factor, yielding a view on the screen to match that of the final product. For proper operation of this function, the screen pixel pitch must be correctly specified in the initialization file for the monitor size and pixel count in effect. Zoom Re-center. This selection is used to move a desired viewpoint to the center of the display screen without changing the magnification factor. Zoom Re-draw. This selection is used to regenerate the display screen without changing the magnification factor or viewpoint. If you have been moving or editing overlapping or intersecting objects, the display screen tends to acquire a mottled appearance. At any time during such editing, the screen can be cleaned up simply and easily by this function. Zoom Layer. This selection is used to select a new active layer to be used for viewing and editing. A pop-up dialogue box appears to allow the selection of the new view layer. Once a new layer is selected, that single layer is regen-erated so as to be prominently displayed on the screen. Zoom Limits. This selection is used to snap the zoom scaling factor to a value such that the entire usable workspace is visible at one time. Zoom Extents. This selection is used to snap the zoom scaling factor to a value such that all file elements are visible at one time at the largest magnification possible. Zoom Window. This selection is used to snap the zoom scaling factor to a value such that all of a specified rectangular region is visible on the display screen.