Some Applications Hardware Implemntation
Logic microoperations are very useful for manipulating individual bits or a portion of a word stored in a register. They can be used to change bit values, delete a group of bits, or insert new bit values into a register. The following examples show how the bits of one register (designated by A) are manipulated
by logic rnicrooperations as a function of the bits of another register (designated by B). In a typical application, register A is a processor register and the bits of register B constitute a logic operand extracted from memory and placed in register B.
Frequently Asked Questions
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Ans: The hardware implementation of logic rnicrooperations requires that logic
gates be inserted for each bit or pair of bits in the registers to perform the
required logic function. Although there are 16 logic rnicrooperations, most
computers use only four-AND, OR, XOR (exclusive-OR), and complementfrom
which all others can be derived. view more..
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Ans: There are 16 different logic operations that can be performed with two binary
variables. They can be determined from all possible truth tables obtained with
two binary variables as shown in Table 4-5. In this table, each of the 16 columns
F0 through F15 represents a truth table of one possible Boolean function for the view more..
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Ans: Logic microoperations specify binary operations for strings of bits stored in
registers. These operations consider each bit of the register separately and treat
them as binary variables. For example, the exclusive-OR microoperation with
the contents of two registers . view more..
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Ans: Logic microoperations are very useful for manipulating individual bits or a
portion of a word stored in a register. They can be used to change bit values,
delete a group of bits, or insert new bit values into a register. view more..
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Ans: The selective-set operation sets to 1 the bits in register A where there are
corresponding 1's in register B. It does not affect bit positions that have D's in
B. The following numerical example clarifies this operation. view more..
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Ans: Shift rnicrooperations are used for serial transfer of data. They are also used
in conjunction with arithmetic, logic, and other data-processing operations.
The contents of a register can be shifted to the left or the right. At the same
time that the bits are shifted, the first flip-flop receives its binary information
from the serial input view more..
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Ans: Instead of having individual registers performing the microoperations directly,
computer systems employ a number of storage registers connected to a common
operational unit called an arithmetic logic unit, abbreviated ALU. view more..
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Ans: In this chapter we introduce a basic computer and show how its operation can
be
puter
specified with register
is defined by its internal
transfer
registers,
statements.
the limirlg
The otganization
and control
of
structure,
the comand
the set of instructions that It uses. The design of the computer is then
carried out in detall. Although the basic computer presented in this chap view more..
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Ans: An instruction code is a group of bits that instruct the computer to
perform a specific operation. It is usually divided into parts, each having its
own particular interpretation. The most basic part of an instruction code is its
operation part. The operation code of an instruction is a group of bits that
define such operations as add, view more..
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Ans: The simplest way to organize a computer is to have one processor register and
an instruction code format with two parts. The first part specifies the operation
to be performed and the second specifies an address. The memory address tells
the control where to find an operand in memory. This operand is read from
memory and used as the data to be operated on together with the data stored
in the processor register view more..
+
Ans: In this chapter we introduce a basic computer and show how its operation can
be
puter
specified with register
is defined by its internal
transfer
registers,
statements.
the limirlg
The otganization
and control
of
structure,
the comand
the set of instructions that It uses. The design of the computer is then
carried out in detall. Although the basic computer presented in this chapter is
very small compared to commercial computers, It has the advantage of being
simple enough so we can demonstrate the design process without too many
complications. view more..
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Ans: It is sometimes convenient to use the address bits of an instruction code not
as an address but as the actual operand. When the second part of an instruction
code specifies an operand, the instruction is said to have an immediate
operand. view more..
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Ans: Computer instructions are normally stored in consecutive memory locations
and are executed sequentially one at a time. The control reads an instruction
from a specific address in memory and executes it. It then continues by reading
the next instruction in sequence and executes it, and so on. view more..
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Ans: The memory address register (AR) has 12 bits since this is the width of
a memory address. The program counter (PC) also has 12 bits and it holds the
address of the next instruction to be read from memory after the current
instruction is executed. The PC goes through a counting sequence and causes
the computer to read sequential instructions previously stored in memory.
Instruction words are read and executed in sequence unless a branch instruction
is encountered. view more..
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Ans: The basic computer has eight registers, a memory unit, and a control unit. Paths must be provided to transfer information from
one register to another and between memory and registers. view more..
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Ans: The input data and output data of the memory are connected to the
common bus, but the memory address is connected to AR. Therefore, AR must
always be used to specify a memory address. By using a single register for the
address, we eliminate the need for an address bus that would have been
needed otherwise. The content of any register can be specified for the memory
data input during a write operation. Similarly, any register can receive the data
from memory after a read operation except AC . view more..
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Ans: The basic computer has three instruction code formats, as shown in Fig. 5-5.
Each format has 16 bits. The operation code (opcode) part of the instruction
contains three bits and the meaning of the remaining 13 bits depends on the
operation code encountered. view more..
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Ans: Before investigating the operations performed by the instructions, let us discuss
the type of instructions that must be included in a computer. A computer
should have a set of instructions so that the user can construct machine
language programs to evaluate any function that is known to be computable.
The set of instructions are said to be complete if the computer includes a
sufficient number of instructions in each of the following categories: view more..
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