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AN INTRODUCTION TO VHDL

Designing Hardware with Software

by James Antonakos

Start ý Levels of Design ý The Interface ý The Body ý Full_Adder ý Half _Adder ý Identifiers, Data Types, and Operators ý Examples ý The Five-Input AND Gate ý The 2:4 Decoder ý Timing Examples ý Other Methods ý Sources and PDF

OTHER METHODS
Typing in a VHDL source file for a large design would be tedious. Most design tools now offer several ways to input a design. Graphical design entry allows you to draw a schematic of the circuit or specify its operation through a state diagram. It is even possible to specify the operation of the digital circuit by entering its input and output waveforms and letting the design tool determine the logic required.

AND THE POINT IS?

After going through the trouble of entering your design, what is next after you successfully compile and simulate it? The nice part is that when youýre finished, the same software that helped you develop your design in a virtual environment will control your real-world PLD programmer and program your design into a real piece of hardware. Here are some of the device types supported by VHDL compilers:

ý AlteraýAPEX 20K, FLEX 6000/8000/10K, MAX 5000/7000/9000

ý XilinxýXC4000 FPGA, XC9500 CPLD

Several thousand gates are common in many of these devices, with some offering over 100,000 gates. Once again, a little effort searching the web will reward you with a long list of devices, manufacturers, and support.

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