Exercises
- Rearrange the circuit in Figure 2.5 to convert the AND gate to a NAND gate. Hint: there is no need to add or remove components.
- Create a circuit implementation of an OR gate by modifying the circuit in Figure 2.5. Wires, transistors, and resistors can be added as needed.
- Search the internet for free VHDL development software suites that include a simulator. Get one of these suites, set it up, and build any simple demo projects that come with the suite to ensure it is working properly.
- Using your VHDL tool set, implement the 4-bit adder using the code listings presented in this chapter.
- Add test driver code (search the internet for VHDL testbench to find examples) to your 4-bit adder to drive it through a limited set of input sets and verify that the outputs are correct.
- Expand the test driver code and verify that the 4-bit adder produces correct results for all possible combinations of inputs.
