This example describes a two input parameterized adder/subtractor design in VHDL. The design unit multiplexes add and subtract operations with an
addnsub input. Synthesis tools detect add and subtract units in HDL code that share inputs and whose outputs are multiplexed by a common signal. Software infers
lpm_addsub megafunction for such add/subtract designs.
Figure 1. Adder/Subtractor Top-Level Diagram
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The use of this design is governed by, and subject to, the terms and conditions of the Altera Hardware Reference Design License Agreement.
Table 1 lists the ports and gives a description for each.
|Table 1. Adder/Subtractor Port Listing|
||Input||4-bit data inputs to adder/subtractor|
||Input||Multiplexing input for add and subtract operations|
||Output||5-bit output along with 1-bit carry/borrow|
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