04-02-2013, 10:53 AM
ADDERS
THEORY:
A half adder has two inputs, generally labelled A and B, and two outputs, the sum S and
carry C. S is the two-bit XOR of A and B, and C is the AND of A and B. Essentially the
output of a half adder is the sum of two one-bit numbers, with C being the most significant
of these two outputs. A half adder is a logical circuit that performs an addition operation
on two binary digits. The half adder produces a sum and a carry value which are both
binary digits.The drawback of this circuit is that in case of a multibit addition, it cannot
include a carry.
A full adder has three inputs - A, B, and a carry in C, such that multiple adders can be
used to add larger numbers. To remove ambiguity between the input and output carry
lines, the carry in is labelled Ci or Cin while the carry out is labelled Co or Cout. A full
adder is a logical circuit that performs an addition operation on three binary digits. The
full adders produces a sum and carry value, which are both binary digits
PROCEDURE:
1). To start working with the program go to the Start-Programs-ActiveHDL7.2 SE
program group and click the Active-HDL7.2 SE. The Active-HDL7.3 should start
loading.
2). Ensure that the Create new workspace option is checked and click the OK button.
It will create a new workspace. Enter the workspace name. Select the location of your
workspace folder. Then Click OK.
3).New Design Wizard has three options. Here ensure that the Create an empty
design is checked and click Next button. It will go to next step to specify additional
information about the new design.
4). Keep the default options and click Next to specify basic information about the
new design.
5). In the Type the design name, enter a name. Also type or select the desired location
of the design folder in the appropriate field.
6) Click the Next button to advance to the next page. Then click Finish and this will
bring out the Design Flow Manager. The next paragraph introduces the Design
Browser.
7). The Design Browser is a window showing the design contents. Double-click the
Add New File in Design Browser to Add New File ( file name) in the Name item. Then
click OK to get an empty VHDL file. (Make sure that the VHDL Source Code icon is
highlighted in the Empty Files field.)
8). Now we can edit the VHDL code. The HDL Editor is a text editor with VHDL
keywords coloring and standard editing features.
9). Select (filename).vhd in the Design Browser, then go to the Design menu, click the
Compile option from the menu or press F11 to compile (filename).vhd file. If there is
any error, the file icon changes to red error, erroneous lines are underlined and the
VHDL console window contains the error description. You need to correct the error
based on the error information in the VHDL Console.
10). To begin a simulation, you have to first initialize the simulator using the Initialize
Simulation option from the Simulation menu.
After the simulator has been initialized, you have to open a new Waveform window.