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1. Integrated Circuits Integrated circuits (ICs) are chips, pieces of semiconductor material, that contain all of the transistors, resistors, and capacitors necessary to create a digital circuit or system.

2. Depending on the No. of Gates present in the ICs, the classification of IC: SSI(Small-Scale Integration) - contain several independent gates in a single package. - The no. of gates are usually less than 10. MSI(Medium-Scale Integration) - Approx. 100 to 200 gates. - ex- decoders, adders, registers.

3. LSI(Large-Scale Integration) - contains 200 to few thousands of gates. - ex- Digital systems such as processors, memory chips. VLSI(Very Large-Scale Integration) - contains thousands of gates in a single package. - ex- complex microcomputer chips, large memory arrays.

4. Digital Logic Family Based on the circuit technology to which the IC belong, the following are the most popular digital logic families: TTL - Transistor-transistor Logic ECL – Emitter-coupled Logic MOS – Metal-oxide semiconductor CMOS – Complementary metal-oxide semiconductor

5. TTL - Transistor-transistor Logic Most widely used and standard logic family. Evolution of DTL(Diode transistor Logic). Variations of TTL: - High speed TTL - Low power TTL - Schottky TTL - Low-power Schottky TTL - Advanced Schottky TTL The power supply voltage for TTL circuits is 5 volts and two logic levels are approx. 0 & 0.3 volts

6. ECL – Emitter-coupled Logic Provides highest speed digital circuits as ICs. Used in systems where high speed is essential. Ex- super computer, signal processors. very fast operation - propagation delays of 1ns or less high power consumption, perhaps 60 mW /gate

7. MOS – Metal-oxide semiconductor MOS logic is vastly used in LSI and VLSI devices. MOS logic family implements the logic gates using MOSFET(MOS Field Effect Transistor). MOS logic gates can be fabricated using either only NMOS or only PMOS devices. NMOS – N-Channel MOS PMOS – P-Channel MOS

8. CMOS – Complementary metal-oxide semiconductor Considerably lower energy consumption than TTL and ECL most widely used family for large-scale devices combines high speed with low power consumption usually operates from a single supply of 5 – 15 V can be connected to a large number of gates (about 50)

9. Decoders A decoder is a combinational circuit that converts binary information from the n coded inputs to a maximum of 2^n unique outputs. N inputs and 2^N outputs. A decoder selects one of the 2^N outputs by decoding the binary value on the N inputs. Exactly ONE output will be active for each combination of the inputs.

10. 3 to 8 line Decoder 3*8 line Decoder 3 Inputs 8 outputs A0 A1 A2 D0 D1 D2 D3 D4 D5 D6 D7 E Enable Input

11. Truth Table for 3 to 8 line decoder:

12. 3 to 8 line decoder: Binary to Octal Converter

13. 2 to 4 line Decoder 2*4 line Decoder 4 outputs A0 A1 D0 D1 D2 D3 E Enable Input 2 Inputs

14. NAND Gate Decoder

15. Decoder Expansion:

16. Encoder An Encoder is a digital circuit that performs the reverse operation of decoder. An Encoder has 2^N input lines and N output lines. The output lines generate the binary codes corresponding to the input value. The encoders are implemented with OR gates.

17. 2^n : n line Encoder N outputs A2 2^N Inputs . . . . . .

18. 8 : 3 line Encoder(Octal to Binary encoder)

19. A0 = D1 + D3 + D5 + D7 A1 = D2 + D3 + D6 + D7 A2 = D4 + D5 + D6 + D7

20. Multiplexers A multiplexer is a combinational circuit that receives binary information from one of 2^n input data lines and directs it to single output line. The selection of particular input data line for the output is determined by a set of selection inputs . A 2^n to 1 MUX has 2^n input data lines and n input selection lines whose bit combinations determine which input data are selected for the output. A MUX is also called as Data Selector since it selects one of many data inputs and directs the binary information to the output.

21. Block Diagram of MUX

22. 4 : 1 line Multiplexer Function Table for 4:1 line MUX Selection Mode Output S 0 S 1 ‘Y’ 0 0 I 0 0 1 I 1 1 0 I 2 1 1 I 3

23. 8 : 1 line MUX Function Table for 8:1 line MUX Selection Mode Output S 0 S 1 S 2 ‘Y’ 0 0 0 I 0 0 0 1 I 1 0 1 0 I 2 0 1 1 I 3 1 0 0 I 4 1 0 1 I 5 1 1 0 I 6 1 1 1 I 7

24. Registers

25. 4 bit Register:

26. 4 bit register with parallel load:

27. Shift Registers 4 bit Shift Register:

28. Bidirectional shift register with parallel load:

29. Binary Counters

30. Memory Unit A memory unit is a collection of storage cells with associated circuits needed to transfer information in& out of storage. The memory stores binary information in groups of bits called words. Special input lines called address lines select one particular word where the information is to be stored. Each word in the memory is assigned an identification number, called as address( 0 to 2^k – 1 ) The selection of specific word inside the memory is done by applying the binary address of the word to the address line. A decoder inside the memory accepts this address and opens the paths needed to select the bits of the specified word. Two major types of memories are RAM and ROM

31. RAM(Random-Access memory) In RAM, memory cells can be accessed for information transfer from any desired random location. Ram is volatile. N data input lines provide the information to be stored in the memory. N data output lines supply the information coming out of the memory. K address lines specify the particular word address among 2^k words. Read & Write are the control inputs that specify the direction of desired transfer.

32. The two operations the RAM can perform are: Write & Read On accepting one of these signals, the internal circuits inside the memory provide the desired function. Steps to transfer new word to be stored into the memory: - Apply the binary address of the desired word into the address lines. - Apply the data bits that must be stored in the memory into the data input lines. - Activate the write input.

33. Steps to transfer a stored word out of memory: Apply the binary address of the desired word into the address lines. Activate the read input.

34. ROM(Read-Only memory) A ROM is a memory unit that performs the read operation only; it does not have a write capability. The binary information stored in the ROM is made permanent during the hardware production of the unit. ROMs comes with a special internal electronic fuses that can be programmed for a specific configuration. ROM is non-volatile.

35. Types of ROMs: PROM : The users are allowed to program PROMs in their work stations. The fuses are blown by application of current pulses. EPROM : The stored contents are erased when EPROM is placed under a special UV ray/light for a given time period. EEPROM : The contents of the EEPROMs can be erased with electrical signals instead of UV light.