Creating Multiple Symbols for One Library Unit

Introduction

Active-HDL allows creation of multiple symbols for one library unit (VHDL entity, Verilog module, etc.). To justify having multiple, different symbols for one unit on one block diagram we can mention one register block that is used as internal register, input register and output register. Three different symbols increase readability of the diagram in this case.

Compilation

To do any kind of symbol editing, you have to compile your VHDL or Verilog source of the library unit. This document uses VHDL entity reg8, but all procedures are the same in case of Verilog module reg8.

Opening Symbol Editor

To start first symbol editing session, right-click the compiled unit symbol in the Design Browser, Files tab and select Edit Symbol from the pop-up menu. You can click compiled unit symbol either underneath unit source or in the design library section, as shown in Figure 1. If the symbol for the unit is already placed on a block diagram, you can right-click the symbol and select Edit Symbol in Separate Window from the pop-up menu.

Figure 1: Design Browser - compiled library unit

Saving Default Symbol

To simplify future operations on symbols, we recommend saving the default shape of the symbol with a proper description in the design library. To do so:

  1. Right-click the symbol in the Symbol Editor window and select Symbol Properties from the pop-up menu (see Figure 2 below).

    Figure 2: Symbol Properties Menu

  2. Find the Description field at the bottom of the General tab in the Symbol Properties window.

    Figure 3: Symbol Properties Window

  3. Enter desired, brief description of the symbol, e.g. “Default” (Figure 3).

  4. Click OK to update the description.

  5. Click Save button in the toolbar (or hit Ctrl+S on your keyboard) to save modified symbol.

From now on, you should be able to see the symbol name and description in the Symbol Toolbox within the Block Diagram Editor and Library Manager window.

Adding Another Symbol

While still in the Symbol Editor window, you can modify symbol shape, color, text, etc. In our case, we will change the symbol background color and add “Out” text in the corner.

To change symbol background:

  1. Right-click the symbol in the Symbol Editor window and select Edit Symbol Background from the pop-up menu.

  2. Click the symbol background so its outline turns red.

  3. Click the Fill Color (“bucket”) icon in the bottom toolbar of the Symbol Editor window and pick new color, e.g. light orange.

    Figure 4: Background Color Selection

  4. Right-click the symbol in the Symbol Editor window and click Edit Symbol Background in the pop-up menu to remove check mark.

To add “Out” text in the corner:

  1. Click the Text (“letter A”) icon in the top toolbar of the Symbol Editor window.

  2. Click inside the symbol, close to its lower right-hand corner to see text cursor.

  3. Type the desired text, e.g. “Out”.

  4. Click the Select (“arrow”) icon in the top toolbar of the Symbol Editor window; your text should now have a red outline.

  5. Reposition the text if needed.

Before saving the new symbol, always remember to modify the symbol description. In some contexts, graphical symbol preview is not possible, so a proper description is the only way of distinguishing different symbols.

To modify symbol description:

  1. Right-click the symbol in the Symbol Editor window and select Symbol Properties from the pop-up menu.

  2. Find the Description field at the bottom of the General tab in the Symbol Properties window.

  3. Enter desired, brief description of the symbol, e.g. “Orange - Out”.

  4. Click OK to update the description.

To add new symbol to the library unit:

  1. Select File | Save to Library As from the main menu (Figure 5).

    Figure 5: Save to Library As menu

  2. Select the Add new symbol shape check box at the bottom of the Save Symbol window.

  3. Click Save in the Save Symbol window (Figure 6).

    Figure 6: Save Symbol window

Your new symbol is now saved alongside the original one in the design library.

You can repeat the procedures listed in this section to create another symbol, e.g. “Blue – In” with light blue background and “In” text in the corner.

Accessing New Symbols

New, multiple symbols can be accessed from the Symbol Toolbox in the BDE window, from where they can be dragged to the diagrams.

Figure 7: Block Diagram with multiple symbols

If you select the design library in the Library Manager window, then clicking the library unit name in the right pane opens the list of available symbols at the bottom of the window. From that list, you can set symbol as default, open it for editing, export, import, copy, and delete it.

Figure 8: Library Manager with multiple symbols for one unit.

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