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Circuit Description

This applet demonstrates a 9-bit ripple-carry ALU (adder/subtractor) automatically created by a C++ program. That is, the Hades design file(s) for the ALU was not entered manually via the schematics editor, but was directly written by a generator program. Run the generator code and enter the bit-width N, and a new design will be created.

When started, the program first queries for the bit-width (N), calculates the required circuit structure, and then writes the corresponding Hades design file (called 'sum_Nbits.hds'). The example circuit shown in this applet was created by the generator with N=9.

Click (or shift-click) the input switches to select the input values for the ALU, select the function (add/sub), and watch the result values. If necessary, use the popup-menu (zoom, zoom-region) to enlarge the area (left center) with the input switches and the output display.

Note that no explicit signal wires are visible in the circuit schematics. When writing the Hades design file for the ALU, the generator program just creates the logical connections ('signals') between the inputs, adders, XOR-gates, and outputs, but it does not create extra graphical objects ('wire segments, solder dots'). Also, the generator uses a simple left-to-right placement strategy for the gates (resulting in rather wide schematics when N>6 or so). Internally, the simulator uses the logical connections and does not need a schematics at all.

The program generator is available on the following compressed archive (tar.gz format). This generator has been written by the computer science student Fred Paulino Ferreira from Universidade Federal de Viçosa, Brazil.