Digital Logic Design Ch1-1

Digital Logic Design Ch1-2 Introduction to digital logic (logic gates, flip-flops, circuits) Definition of Digital Logic  Digital logic consists of binary variables and a set of logical operations.  The variables are designated by letters of the alphabet, such as A, B, C, x, y, z, etc, with each variable having two and only two distinct possible values: 1 and 0,

Digital Logic Design Ch1-3 Digital systems are said to be constructed by using logic gates. These gates are divided of three types of gate: 1- Basic gates: AND gate OR gate NOT gate 2- Universal gates: NAND gate NOR gate 3- Derived gates: EXOR gate EXNOR gates.

Digital Logic Design Ch1-4 xyz * AND gate z = x y = x y The AND gate is an electronic circuit that gives a high output (1) only if all its inputs are high. A dot (.) is used to show the AND operation i.e. A.B.

Digital Logic Design Ch1-5 xyz * OR gate z = x + y The OR gate is an electronic circuit that gives a high output (1) if one or more of its inputs are high. A plus (+) is used to show the OR operation

Digital Logic Design Ch1-6 xz * NOT gate X =Z=X The NOT gate is an electronic circuit that produces an inverted version of the input at its output. It is also known as an inverter. If the input variable is A, the inverted output is known as NOT A. This is also shown as A', or A with a bar over the top.

Digital Logic Design Ch1-7 Switching Circuits SW1SW2Lamp SW1 SW2 Lamp off on off on off on

Digital Logic Design Ch1-8 SW1 Switching Circuits SW1SW2Lamp SW2 Lamp off on off on

Digital Logic Design Ch1-9 Switching Circuits SWLamp SW Lamp off on off on

Digital Logic Design Ch1-10 Binary Logic Logic gates  Example of binary signals Logic 1 Logic 0 Un-define Figure 1.3 Example of binary signals

Digital Logic Design Ch1-11 Binary Logic Logic gates  Graphic Symbols and Input-Output Signals for Logic gates: Fig. 1.4 Symbols for digital logic circuits Fig. 1.5 Input-Output signals for gates

Digital Logic Design Ch1-12 In PutOut Put The NAND gate represents the complement of the AND operation. Its name is an abbreviation of NOT AND.

Digital Logic Design Ch1-13 In PutOut Put The NOR gate represents the complement of the OR operation. Its name is an abbreviation of NOT OR.

Digital Logic Design Ch1-14 In PutOut Put The output is high when either of inputs A or B is high, but not if both A and B are high. It is consists of a five gates (two AND, two NOT, and one OR)

Digital Logic Design Ch1-15 In PutOut Put This is an X-OR gate with the output inverted. It is consists of a five gates (two AND, two NOT, and one OR)

Digital Logic Design Ch More about logic gates To implement a logic gate in hardware, you use a transistor Transistors are all enclosed in an “IC”, or integrated circuit The current Intel Pentium IV processors have 55 million transistors!

Digital Logic Design Ch1-17

Digital Logic Design Ch1-18 A digital circuit that contains flip-flops is called a Sequential Circuit A flip-flop holds a single bit of memory  The bit “flip-flops” between the two NAND gates In reality, flip-flops are a bit more complicated  Have 5 (or so) logic gates (transistors) per flip- flop

Digital Logic Design Ch R-S flip-flop 2- D flip-flop 3- J-K flip-flops R S

Digital Logic Design Ch Flip-flops R-S Flip-Flope Consider the following circuit: R S Q Q RS Function 10Reset 01Set 11Hold 001/1 holds it’s a single bit of memory.