Computer Organization assembly

1. Course Code: CE-101
Credit Hour: 2+1
Prerequisite: DLD
Kanza Ali
Email: kanza_29@yahoo.com
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2. Day Time Class Room No
Tuesday 11:00 to 12:00 Class Room 6
Wednesday 11:00 to 1:00 MP Lab
Thursday 12:00 to 1:00 Class Room 5
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3. 3

4.  There must be a
mechanism to inform
memory that we want to do
the
read operation
 There must be a
mechanism to inform
memory that we want to
read
precisely which element
 There must be a
mechanism to transfer
that data element from
memory to processor
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5. 5

6. Address Bus
 The address bus is unidirectional and address
always travels from processor to memory
Data Bus
 Data moves from both, processor to memory and
memory to processor, so the data bus is
bidirectional
Control Bus
 information from the processor to a peripheral
and some take information from the peripheral to
the processor
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7.  A binary number is generated on the address
bus, fifth, seventh, eighth, tenth; the cell
which is needed
 A memory cell is an n-bit location to store
data, normally 8-bit also called a byte
 The number of bits in a cell is called the cell
width
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8. 00000000
00000001
.
. . Vertical
Binary . . Dimension=Size
Addresses .
. of Memory
of Memory .
. .
Cells
. .
00100011
00100100
00100101
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9.  Precise synchronization between the
processor and the memory is the
responsibility of the control bus
 Since the memory never wants to listen or to
speak of itself. Then why is the control bus
bidirectional.
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10.  There are temporary storage places inside the
processor called registers
 Registers are inside the processor
 They are used when we need more than one
data element inside the processor at one time
 In its operation it is similar to memory
 It is also knows as scratch pad ram
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11.  Memory is a limited resource but the number
of memory cells is large
 Registers are relatively very small in number,
and are therefore a very scarce and precious
resource
 Registers are more than one in number, so
we have to precisely identify or name them
 Some manufacturers number their registers
like r0, r1, r2, others name them like A, B, C,
D etc. 11
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12.  There is a central register in every processor
called the accumulator
 Traditionally all mathematical and logical
operations are performed on the accumulator
 The word size of a processor is defined by
the width of its accumulator. A 32bit
processor has an accumulator of 32 bits
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13. It does not hold data but holds the address of
Data
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14.  This is a special register in every architecture
called the flags register
 Collection of different Boolean information each
bit has an independent meaning
 Like the accumulator it is an 8, 16, or 32 bits
register but unlike the accumulator it is
meaningless as a unit, rather the individual bits
carry different meanings
 The bits of the accumulator work in parallel as a
unit and each bit mean the same thing
 The bits of the flags register work independently
and individually, and combined its value is
meaningless
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16.  A program is defined to be “an ordered set of
instructions.”
 Instructions have a positional relationship.
The whole logic depends on this positioning
 “The program counter holds the address of
the next instruction to be executed.”
 This number is called the opcode.
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17.  Symbols are called instruction mnemonics
add, sub, lad
 The dumb translator that will convert these
mnemonics back to the original opcodes is a
key program to be used throughout this
course and is called the assembler
Add to 152 or some numbers
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18. 18

19.  These instructions are used to move data
from one place to another.
 These places can be registers, memory, or
even inside peripheral devices. Some
examples are:
mov ax, bx ; move data from bx to ax
lad 1234 ; laod 0234 into accumulator
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20.  Arithmetic instructions like addition, subtraction,
multiplication, division and Logical instructions like
logical and, logical or, logical xor, or complement
are part of this group. Some examples are:
and ax, 1234 ; AND 1234 with ax
add bx, 0534 ; AND 0534 to bx
add bx, [1200] ; ADD data at address 1200 to bx
The bracketed form is a complex variation meaning to
add the data placed at address 1200.
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21. These are instructions that control the
program execution and flow by playing with
the instruction pointer and altering its normal
behavior to point to the next instruction.
cmp ax, 0 ; compare ax with 0
jne 1234 ; jump if not equal to the
; instruction at address 1234
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22. Another group called special instructions works
like the special service commandos. They allow
changing specific processor behaviors and are
used to play with it. They are used rarely but
are certainly used in any meaningful
program.
cli ; clear the interrupt flag
sti ; set the interrupt flag
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