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Showing posts from January, 2011

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

Active HDL 7.2 Student Edition for VHDL

If you are a student and if you want to design digital circuits and to learn VHDL/Verilog, then download the Active HDL 7.2 Student Edition. The Size of the file comes around 140MB. Install as per the recommended settings. Once installed, without license file the application wont open. You need to register to get the license file. The file would be sent to our email Id or directly after registration we can download the file in the web page itself. The license file is applicable only for that machine. If the software has to be installed on another machine, another license you need to download. Copy the license_student.dat file in the following folder C:\Program Files\Aldec\Active-HDL 7.2SE\Dat. And now the application can be opened and digital circuits can be simulated

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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

Radix Complement and Diminished Radix complement

Complements are used in digital computers for simplifying the subtraction and for logical manipulations. There are two types of complement Radix complements ( r complement) diminished radix complements (r-1 complement) For base 2 or binary number system the r’s complement is 2’s complement and ( r-1)’s complement is 1’s complement For base 10 or decimal system the r’s complement is 10’s complement and (r-1)’s complement is 9’s complement. 10’s Complement Let us assume the number 3567890, for finding the 10’s complement, there is a rule 3 5 6 7 8 9 0 Most significant Digit Least Significant Digit 10’s complement can be obtained by leaving all least significant 0’s unchanged subtracting the first non zero least significant digit from 10 and subtracting all higher significant digits from 9 For the above exampl

Number Conversion

Number conversion is the fundamental operation of any digital systems. There are different bases like base2, base8, base10 and base 16 Base – 10 Base 2 (Binary) Base 8 (Octal) Base 16 (Hexadecimal) 0 0000 00 0 1 0001 01 1 2 0010 02 2 3 0011 03 3 4 0100 04 4 5 0101 05 5 6 0110 06 6 7 0111 07 7 8 1000 10 8 9 1001 11 9 10 1010 12 A 11 1011 13 B 12 1100 14 C 13 110