Microcomputer Architecture and Logic Design

 Register Memory Register memory is the smallest and fastest memory o n your computer. It is not part of main memory , but is located o n the CPU in the form of registers, which are the smallest data holding elements. R egister s temporarily s tore frequently used data, co mma n d s, and memory addresse s used by the CPU. H olds the command currently being processed from the CPU. All data m u s t pass through registers before it can be processed. Theref o re , i t is used to process the data entered by the user from the CPU . The r egister hold s a small amount of data , a b ou t 32 to 64 bits. The speed of the CPU depends on the number and size (n umber of bits) of the registers built into the CPU. Registers can be of va r ious types d e pen d ing on the application. W idely used r egisters include a ccumulator s or AC s , d ata r egisters and DRs, address registers or ARs, program count e rs (PCs), and I / O address registers . Types and Functi

    R-2R DAC This is Combinational Logic Circuit The R-2R Digital-to-Analogue Converter, or DAC, is a data converter that converts a digital binary number into an analogue output signal proportionate to the digital number's value using two precision resistors. R-2R DAC Circuit with Four Zero (LOW) Inputs (RF/RIN)*VIN is the output voltage of an inverting operational amplifier. If we set RF equal to R, RF = R = 1, and R is connected to ground (0V), there is no VIN voltage value (VIN = 0), hence the output voltage is (1/1)*0 = 0 volts. As a result, the output voltage of a 4-bit R-2R DAC with four grounded inputs (LOW) will be “zero” volts, and a 4-bit digital input of 0000 will yield an analogue output of 0 volts. So, if we link input bit VA HIGH to +5 volts, what happens? What is the R-2R ladder network's equivalent resistive value, as well as the op-output amp's voltage? R-2R DAC with Input V B   The output voltage, VOUT, is computed at 625mV, which is one-eighth (1/8th) th

  Counters   a counter is a device which stores (and sometimes displays) the number of times a particular event or process has occurred, often in relationship to a clock. The most common type is a sequential digital logic circuit with an input line called the clock and multiple output lines. The values on the output lines represent a number in the binary or BCD number system. Each pulse applied to the clock input increments or decrements the number in the counter. A counter circuit is usually constructed of a number of flip-flops connected in cascade. Counters are a very widely used component in digital circuits, and are manufactured as separate integrated circuits and also incorporated as parts of larger integrated circuits. There are 2 types 1)         Synchronous   2)       Asynchronous                         How to create   Asynchronous  4 bit Up Counter &   Asynchronous  4 bit down Counter                                   UP COUNTER            DOWN COUNTER   BCD or Decad

Multiplier     2 bit Multiplier A Binary Multiplier is a digital circuit used in digital electronics to multiply two binary numbers and provide the result as output. The method used to multiply two binary numbers is similar to the method taught to school children for multiplying decimal numbers which is based on calculating partial product, shifting them and adding them together. Similar approach is used to multiply two binary numbers. Long multiplicand is multiplied by 0 or 1 which is much easier than decimal multiplication as product by 0 or 1 is 0 or same number respectively. Figure 1 below shows the block diagram of a 2-bit binary multiplier. The two numbers A1A0 and B1B0 are multiplied together to produce a 4-bit output P3P2P1P0.    

  Frequency Divider It called as Clock divider That circuit  takes an input signal of a  frequency  and generates an output signal of a frequency Frequency  is the number of occurrences of a repeating event per  unit of time Create Frequency divider using JK Flip Flops  A frequency divider can be constructed from J-K flip-flops by taking the output of one cell to the clock input of the next. The J and K inputs of each flip-flop are set to 1 to produce a toggle at each cycle of the clock input. For each two toggles of the first cell, a toggle is produced in the second cell, so its output is at half the frequency of the first. The output of the fourth cell is 1/16 the clock frequency. The same device is useful as a binary counte r Create & Simulate        

  Sequential Logic Circuit Sequential Logic is a combinational logic with memory.  This means that sequential logic circuits are able to take into account their previous input state as well as those actually present Output can vary based on input.  This type of circuits uses previous input, output, clock and a memory element. There are 2 types           1)  Synchronous  types  run with same different pulse                S - R Latch         2)  Asynchronous types run with same clock pulse               S - R Flip Flop S - R Latch S-R Latch Using NOR Gate What is S-R Latch and explanation Create a Circuit & Simulate S-R Latch  Using NAND Gate   Circuit Truth Table   Case 1: R = 1 & S = 1 When both the S and R inputs are HIGH, the output remains in previous state  it holds the previous data. Case 2: R = 1 & S = 0 When R input is HIGH and S input is LOW, the flip flop will be in SET state. As R is HIGH, the output of NAND gate B ,  Q  becomes LOW. This causes both the inputs

De-multiplexer The de-multiplexer is a combinational logic circuit designed to switch one common input line to one of several separate output line. 1 to 4 De-multiplexers

  Multiplexer (MUX)   MUX is a Combinational Logic Circuit with more than one input line, one output line and more than one select line  It accepts the binary information from several input lines or sources and depending on the set of select lines, a particular input line is routed onto a single output line.  Multiplexer acts as a multiple-input and single-output switch It has only one output and   2n  inputs It identified as digital Switch Types of Multiplexers 1) 2 X 1 MUX                          2) 4 X 1 MUX        3) 8 X 1 MUX     1)    2 X 1 MUX    A 2-to-1 multiplexer consists of two inputs D0 and D1, one select input S and one output Y.  Depending on the select signal, the output is connected to either of the inputs. Since there are two input signals, only two ways are possible to connect the inputs to the outputs, so one select is needed to do these operations. If the select line is low, then the output will be switched to D0 input, whereas if select line is high, then the out