1. Chapter 3 (part 2)
Basic Logic Gates 1

2. 3-7 The Inverter Used to complement (invert) a digital signal
When A = 1, X = 0
When A = 0, X = 1
Timing analysis

3. Truth table and Boolean equations for the Inverter
X = A
Inversion bar
Used to signify the complement
Inverter is also called as NOT gate
Truth Table

4. 3-8 The NAND Gate
Same as the AND gate except that its output is inverted
If A = 1 and B = 1, X = 0
If A = 0 or B = 0, A = 1

5. I/O of a 7400 quad NAND IC

6. Truth table and Boolean equations for the NAND Gate
Boolean Equation: X = AB
Multiple inputs - the output is always HIGH unless all inputs go HIGH

7. Symbols for three- and eight-input NAND gates

11. 3-9 The NOR Gate
Same as the OR gate except that its output is inverted
If A = 1 or B = 1, X = 0
If A = 0 and B = 0, X = 1

12. I/O of a 7402 quad NOR IC

13. Truth Table and Boolean equation for The NOR Gate
Boolean Equation: X = A + B

17. 3-10 Logic Gate Waveform Generation
A popular general
Purpose Repetitive
waveform generator
To create specialized waveforms, we use
Basic gates, and
a clock oscillator, and
A repetitive waveform generator circuit

18. Figure 3.44 Generating a 3-ms HIGH pulse using an AND gate and a Johnson shift counter.

19. Example 3-13 Which Johnson counter outputs will you connect to an AND gate to get a 1ms HIGH-level output from 4 to 5ms?

20. Example 3-14 Which Johnson counter outputs must be connect to a three-input AND gate to enable just the Cp#4 pulse only to be output?

21. Example 3-15 Sketch the output waveform resulting from inputting the Johnson counter outputs shown:

26. Figure 3.60 7404 TTL and 4049 CMOS inverter pin configurations.

27. Figure (a) 7402 TTL NOR and 4001 CMOS NOR pin configurations; (b) 7400 TTL NAND and 4011 CMOS NAND pin configurations.

29. 3-12 IEEE/IEC Standard Logic Symbols

31. Summary
The AND gate requires that all inputs are HIGH in order to get a HIGH output.
The OR gate outputs a HIGH if any of its inputs are HIGH.
An effective way to measure the precise timing relationships of digital waveforms is with an oscilloscope or a logic analyzer.

32. Summary
Beside providing the basic logic functions, AND and OR gates can also be used to enable or disable a signal to pass from one point to another.
There are several integrated circuits available in both TTL and CMOS that provide the basic logic functions.

33. Summary
Two important troubleshooting tools are the logic pulser and the logic probe. The pulser is used to inject pulses into a circuit under test. The probe reads the level at a point in a circuit to determine is it is HIGH, LOW, or floating.
An inverter provides an output that is the complement of its input.

34. Summary A NAND gate outputs a LOW when all of its inputs are HIGH.
A NOR gate outputs a HIGH when all of its inputs are LOW.
Specialized waveforms can be created by using a repetitive waveform generator and the basic gates. 40