# Circuit Diagram Editor

Chip circuits can be developed by adding circuit components to a workspace and wiring them together. This is done by the circuit diagram editor.

Logic components available in the circuit diagram editor are AND gates, OR gates, and inverters. The toolbox also includes ground and VCC connections for providing constant '0' and '1' values respectively and input and output pins which map to pins on the chip. These components can be added to the workspace by clicking the buttons in the toolbar or selecting the component from the Insert menu. Holding the mouse pointer over the items in the toolbar causes a tool-tip to appear which identifies the component. Having selected the component it is placed on the workspace by clicking where it should be placed. A ghost of the component follows the mouse pointer until the component is placed. If you have accidentally selected a component that you don't want to place, clicking the mouse pointer button on the left of the toolbar removes the component. If an input or output pin is selected an input dialog will request a label for the pin. This label is the label that will be used for the pin in the breadboard simulator. Labels can also be added to any other part of the circuit by clicking the 'A' button but this has no effect outside of the circuit diagram editor.

Once components have been placed on the workspace they can be moved, deleted or, in the case of labels and pins, renamed. Components are selected by clicking on them (while not in wiring mode). Once they have been selected they can be moved, deleted or renamed by selecting the relevelant option from the Edit menu. Components can also be moved by dragging them with the mouse. If components are moved or deleted then all wires to which they connect will be deleted.

To wire components together you need to be in wiring mode. Wiring mode is started by clicking on the wire button in the toolbox or selecting Enter Wiring Mode from the Wire menu. The wiring mechanism for the circuit diagram editor is the same as in the breadboard simulator. To start drawing a wire click on the start position on the workspace. Move the mouse from this point to draw out a wire. To place a bend in the wire click once and to terminate the wire double-click. If a connection has been successfully made to a component or another wire then a node will appear. To exit wiring mode click on the pointer button in the toolbar or select Exit Wiring Mode from the wire menu. The colour of the wire may be changed by selecting a colour from the wire menu.

The outputs of two components should never be connected unless the outputs are tri-state buffers. At present the circuit diagram editor does not support tri-state buffers, so checks are performed to ensure that drawing a wire would not directly connect outputs. If this occurs the wire is removed and an error message shown in the status bar.

If the circuit diagram editor is not in wiring mode wires can be selected by clicking on them. Once selected they may be deleted by clicking the delete key or selecting delete from the Edit menu. If the deleted wire is connected to others the the connected wires are also removed.

The properties panel at the bottom of the editor should be used for setting additional chip characteristics. For help on the components of the properties panel click here.

Once the chip diagram has been completed the chip file is saved by clicking File -> Create Chip File. Doing so brings up a save dialog box. Select the directory and filename and click Save. The file extension ".chp" will automatically be added. In order to create chip files loading and saving must have been enabled. Click here for more information.

Once the file has been saved the option is given to close the editor. Remember that once the editor has been closed the chip cannot be re-loaded into the editor and any changes will need to be made manually to the chip file. Thus it is advisable to test the chip in the breadboard simulator before closing the table editor.

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