What is 2’S complement?
ANSWER
2’S (Two's) complement is a clever
way of storing integers so that common math problems are very simple to
implement. It is the complement with respect to 2^N;
in other words, it is the result of subtracting the number from 2^N, which is one followed by N zeroes in binary.Two's complement representation
allows the use of binary arithmetic operations on signed integers, yielding the
correct 2's complement results.Two's
complement is a mathematical operation on binary numbers, as well as a
binary signed number representation.
All the positive numbers in 2’s
compliment are represented by the same number while the negative numbers are
represented by the two's complement of their absolute value. . In most cases the two’s compliment of a number
behaves like the negative of that number. The weight of each bit is a power of
two, except for the most significant bit, whose weight is the negative of the
corresponding power of two. In a binary number representation, a
two's-complement number system encodes positive and negative numbers.
"What is ALU"?
ANSWER
Arithmetic Logic Unit (ALU) is the memory unit in a computer
that performs arithmetic functions like addition, multiplication, division and
subtraction or logical operations like AND and OR. Most of the operations of a
CPU are carried out by ALU. It loads data from a small amount of input
available as a part of CPU known as register.
CPU- the principal part of any digital computer
system, is composed of the main memory, control unit, and arithmetic-logic unit
(ALU). It links various peripheral devices such as input/output devices and
auxiliary storage units .The main function of ALU in the CPU is to accept data
from the main memory (“a workmate”) and perform arithmetice.g. multiplication,
addition etc. and logical operationse.g. AND and OR on it. The instruction word
that comes with any input (operation code) tells the ALU what operation to
perform, and operands are used in this case. ALU performs the arithmetic and
logic algorithms selected to process the incoming data. The speed of ALU is
extremely high. It runs in nanoseconds (billionths of a second).
What is Flip-flop and their types? What is
RS latches?
ANSWER
Flip-flop, also called bistable gates, are digital logic
circuits that has two stable states. They remain in their present state
indefinitely until an input pulse called a trigger is received. When a trigger
is received, the flip-flop outputs change state according to defined rules and
remain in those states until another trigger is received. To form the logic
gates for the digital integrated circuits used in memory chips and
microprocessors, there must be an interconnection of the flip flop circuits.
Flip flop can as well be used for data storage, either in binary digits or one
bit of data.
A flip-flop stores a single bit(binary digit) of data; one of its two states represents a
"one" and the other represents a "zero". They can be either
simple (transparent or asynchronous) or clocked (synchronous); the transparent
ones are commonly called latches.
Types of Flip-Flops
§ D (Delay or Data):The D flip-flop is
the memory cell, a delay line or a zero holder. Its function isto capture the
value of the D-input at a definite portion of the clock cycle (such as the rising
edge of the clock).
§ T (Toggle): This changes the state of
the flip flop. When it is high, state changes but when it is low, the previous
value is held.
§ SR (Set-Reset):Thisis
an arrangement of logic gates that maintains a stable output even after the
inputs are turned off.
§ JK: This is the most versatile of the
basic flip flops. It resets the flip flop by using “J” and “K” inputs. If J and
K are different then the output (Q) takes the value of J at the next clock
edge. If they are both low then no change occurs. If they are both high at the
clock edge then the output will toggle from one state to the other. JK if more
or less a T flip flop.
The RS
(Reset Set) latch is a simple memory element that has separate control
lines to set (turn on) or reset (turn off) the latch. Many also
have dual outputs. It is constructed by feeding the outputs of two NOR gates
back to the other NOR gates input. Its function is to reset the latch.
8085 and pin functions described in detail
8085 is an
Intel 8 bit, NMOS microprocessor that uses a single +5V D.C supply for its
operation. It has a clock speed of about 3MHz and the clock cycle is about
320ns. It has 246 opcodes and 80 basic instructions. It consists of several
registers, Arithmetic Logic Unit (ALU), control unit and timing. It generates
control signals and timing which are necessary for its proper operation. Here are
the pins and their functions:
§ Pins
1 and 2: These
pins are used to connect crystal (used for stabilizing frequency) LC circuitry
and RC circuitry to X1 and X2.
§ Pin
3: This pins carries the reset out
signal. In high state, it indicates that the CPU is being reset and it goes to
peripheral chips. When it is powered ON, the peripheral chips and the processor
are reset.
§ Pin
4 and 5:These pins
are used to communicate serial data. Serial data enters through pin 5 and
leaves through pi 4.
§ Pin
6-11:These are
used to balance or control interrupt requests. When two or more requests are
high at a time, these pins arrange them according to their order of importance.
Pin 11 is also known as out pin.
§ Pin
12 to 28: These
carry 8 data bits (the lower bit address).
§ Pin
30: This pin also known as ALE goes to
memory chips to load the address on the address bus and address data bus into
address latch on the memory chips.
§ Pin
29 to 33: They carry
output signal. They indicate whether some operations like memory read,
instruction fetch and memory write is taking place.
§ Pin
31,32 and 34:These
are connected to I/O chips and memory to detect a memory operation and when
instruction is being executed.
§ Pin
35: This pin is used to slow down 8085
in when slow-running peripheral devices are connected to it. When the device is
not ready, it sends a low READY bit to 8085 and it waits. When ready, it sends
a high READY signal to 8085.
§ Pin
36 and 37: Pin 36
carries a RESET IN and RESET OUT signal to pin 3 while pin 37 carries the
system clock.
§ Pin
38 and 40: They
input data from peripheral devices and transfers large amount of data in
limited time.
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