Dld lecture module 04 01

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Digital Logic & Design
Dr. SajjadAhmed Nadeem
Department of Computer Science & IT
University of Azad Jammu & Kashmir
Muzaffarabad
Module-04
— Registers.
— Register Transfer.
— Binary Logic.
— Gates.

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Registers
Functions of Commonly used
Registers
(IR)
(AC)

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RegisterTransfer
— The CU uses Registers to keep track of
various computer sequences.
— Every input or output device must have at
least one register to store the
information transferred to or from the
device.
— An inter-register transfer operation,a
basic operation in digital system, consists
of a transfer of the information stored in
one register to another.
RegisterTransfer

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RegisterTransfer
— The input unit is assumed to have a
keyboard,a control unit, and an input
register.
— Each time a key is struck, the control
enters into the input register an
equivalent 8 bit alphanumeric character
code (assume code is ASCII).
— The information from the input register is
transferred into the eight least significant
cells of a processor register.
RegisterTransfer
— After every transfer, the input register is cleared
to enable the control to insert a new 8 bit code
when the keyboard is struck again.
— Each 8 bit character transferred to the
processor register is preceded by a shift of the
previous character to the next 8 cells on its left.
— When the transfer of characters is completed,
the processor register is full, and its contents
are transferred into a memory register.

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RegisterTransfer
— To process discrete quantities of information in
binary form, a computer must be provided with,
i. Devices that hold the data to be processed.
ii. Circuit elements that manipulate individual
bits of information.
— The device most commonly used for holding
data is register.
— Manipulation of binary variables is done by
means of digital logic circuits.
RegisterTransfer

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RegisterTransfer
— Process of adding two 10 bit binary numbers.
— Memory unit, which normally consists of
thousands of registers, is shown with only 3 of
its registers.
— Processor is shown with 3 registers, R1,R2,R3,
together with Digital Logic Circuit that
manipulate the bits of R1 and R2 and transfer
into R3, their sum.
RegisterTransfer
— Information stored in memory can be
transferred to processor registers, and Results
obtained in processor registers can be
transferred back into a memory register for
storage.
— The registers of a system are the basic elements
for storing and holding the binary information.
— The Digital Logic Circuits process the
information.

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Binary Logic
— Binary Logic deals with variable that take
on two discrete values and with
operations that assume logical meaning.
— Binary logic is used to describe in a
mathematical way, the manipulation and
processing of binary information.
— It is particularly suited for the analysis and
design of digital systems.
— It is also termed as BooleanAlgebra.
Boolean Algebra

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Operator Precedence
Binary logic
— Binary logic deals with variables that take on two
discrete values and operations that assume logical
meaning.
— Logic gates: electronic circuits that operate on one or
more input signals to produce an output signal.
— Example
x y x AND y
0 0 0
0 1 0
1 0 0
1 1 1
16

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Electrical signals
Two values: 0 or 1
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Symbols for digital logic circuits

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Input-Output signals for gates
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Gates with multiple inputs