## Posts

Showing posts from January, 2011

### Photo 23

a pathway at mylapore, chennai

### Photo 22

A shop at Express Avenue mall

### Integrated Circuits

Integrated Circuits IC or Chip Various gates are interconnected to form a circuit 14 to 64 pins for a typical IC   Levels of Integration Small Scale Integration (SSI) Less than 10 gates Medium Scale Integration (MSI) 10 to 100 gates, adders, multiplexers Large Scale Integration (LSI) 100 to few thousands of gates, processors Very Large Scale Integration (VLSI) Thousands of gates, complex computer Chips, memory arrays Digital Logic Families TTL (Transistor – Transistor Logic) Widespread and this is the standard Bipolar ECL (Emitter Coupled Logic ) For high speed operation Bipolar MOS (Metal Oxide Semiconductors) High component density Unipolar CMOS (Complementary Metal Oxide Semiconductors) Useful where Low power consumption is needed unipolar   Characteristics of digital logic families Fan in Number of inputs of an electronic gate Physical logic gates with large fan in are

### Canonical Forms and Standard Forms

Standard Forms each term in the function can have any number of literals. Example, F1 = a +b’c + cde There are 5 variables in F1 (a,b,c,d,e) Canonical form terms should be written as m0, m1… (sum of Products) or M0, M1, M2… (Product of sums). Each term in the canonical form should have all the literals. Example: F1 = ab’c’d’e’ + abcd’e’ + abcde More about Canonical Forms Minterms It is Sum of Products Canonical form is Sum of Minterms three variable minterms are shown below x a b c minterms 0 0 0 0 m0=a’.b’.c’ 1 0 0 1 m1=a’.b’.c 2 0 1 0 m2=a’.b.c’ 3 0 1 1 m3=a’.b.c 4 1 0 0 m4=a.b’.c’ 5 1 0 1 m5=a.b’.c

### Binary Codes

bit is just called as binary digit To represent 2n elements, n bits are needed Here are the following Binary Codes, For example, the BCD code is otherwise called as 8421 code where the 8,4,2,1 are the weights assigned to the digits for number 3 (0011), the weightage will be 0 * 8 + 0 * 4 + 1 * 2 + 1 * 1 in 84-2-1 code, the weights are arranged like this, for example, for number 2 (0110),  it is 0 * 8 + 1 * 4 + 1 * –2 + 0 * –1 similarly the same case for 2421 codes . Excess – 3 is a code which is in excess of 3 in decimal numbers . Error Detection Codes Binary information is usually transmitted from one place to other through wired medium, due to the electromagnetic radiation or external noise, the information bits can be changed (ie 1 to 0 or 0 to 1), in this scenario, there is a provision to check whether the given word or byte is correct or not. Parity bits are used for that. Odd parity or even parity is adopted based on the application, but