This document summarizes a session on register transfer language and microoperations in computer organization and architecture. It defines register transfer language and describes different types of microoperations including logic, arithmetic, shift, and arithmetic logic shift unit operations. Logic microoperations perform binary logic on register bits. Shift microoperations serially transfer data between registers. The document provides examples and applications of these microoperations.

1. CS307PC:Computer Organization
and Architecture (R18 II(I sem))
Department of computer science and engineering
(AI/ML)
Session 4
by
Asst.Prof.M.Gokilavani
VITS
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2. TEXT BOOK:
• 1. Computer System Architecture – M. Moris Mano, Third Edition,
Pearson/PHI.
REFERENCES:
• Computer Organization – Car Hamacher, Zvonks Vranesic, Safea
Zaky, Vth Edition, McGraw Hill.
• Computer Organization and Architecture – William Stallings Sixth
Edition, Pearson/PHI.
• Structured Computer Organization – Andrew S. Tanenbaum, 4th
Edition, PHI/Pearson.
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3. UNIT - I
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Digital Computers: Introduction, Block diagram of Digital Computer,
Definition of Computer Organization, Computer Design and Computer
Architecture.
Register Transfer Language and Micro operations: Register Transfer
language, Register Transfer, Bus and memory transfers, Arithmetic
Micro operations, logic micro operations, shift micro operations,
Arithmetic logic shift unit.
Basic Computer Organization and Design: Instruction codes,
Computer Registers Computer instructions, Timing and Control,
Instruction cycle, Memory Reference Instructions, Input – Output and
Interrupt.

4. Topics covered in session 4
• Register Transfer Language and Micro operations
• Register Transfer language
• Register Transfer
• Bus and memory transfers
• Arithmetic Micro operations
• logic micro operations
• shift micro operations
• Arithmetic logic shift unit
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5. Logic Micro Operation
• Logic micro operations specify binary operations for string 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 micro operation with the contents of
two registers R1 and R2 is symbolized by the statement
• It specifies a logic micro operation to b executed on the individual bits
of th registers provided that the control variable P=1.
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6. Logic Micro Operation
• As a numerical example, assume that each register has four digits. Let the content
of R1 be 1010 and the content of R2 be 1100. The Exclusive- OR micro operation
stated above symbolizes the following logic computation:
• Special symbol are used for logical operations.
• Ʌ Denotes AND symbol and V denotes OR operation.
• When + symbol occur in micro operation if denotes arithmetic addition but it
control signals it denote the OR.
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7. List of Logic Micro Operation
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• 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.
• In this table, each of the 16 columns F0 through F15 represents a truth table of
one possible Boolean function for the two variables x and y.

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9. Hardware Implementation
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• Although there are 16 logic micro operations, most computers use only four — AND, OR, XOR (exclusive-OR),
and complement from which all others can be derived. Figure shows one stage of a circuit that generates the four
basic logic micro operations.

10. Other Applications
• Logic micro operations can be used to manipulate individual bits or a
portion of word in a register.
• Consider the data in a register A. In another register B is bit data that
will be used to modify the content of A.
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11. Other Applications
1. In a selective set operation, the bit pattern in B is used to set certain bits in A
(logic OR operation)
If a bit in B is set to 1, that same position in A gets set to 1, otherwise that bit in A
keeps its previous value.
2. In a selective complement operation, the bit pattern in B is used to complement
certain bits in A
(logic Ex-OR operation)
If a bit in B is set to 1, that same position in A gets complemented from its original
value, otherwise it is unchanged.
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12. Other Applications
3. In a selective clear operation, the bit pattern in B is used to clear certain bits in
A
(B’s one’s Complement)
If a bit in B is set to 1, that same position in A gets set to 0, otherwise it is
unchanged.
4. In a mask operation, the bit pattern in B is used to clear certain bits in AAt
(AND operation)
If a bit in B is set to 0, that same position in A gets set to 0, otherwise it is
unchanged.
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13. Other Applications
• In a clear operation, if the bits in the same position in A and B are the same, they
are cleared in A, otherwise they are set in A
• An insert operation is used to introduce a specific bit pattern into A register, leaving the
other bit positions unchanged. This is done as
• A mask operation to clear the desired bit positions, followed by
• An OR operation to introduce the new bits into the desired positions.
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14. Shift Micro Operations
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• Shift micro operations 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.
• During a shift-left operation the serial input transfers a bit into the rightmost
position. During a shift-right operation the serial input transfers a bit into the
leftmost position.
• There are three types of shifts:
• Logical
• Circular
• arithmetic

15. Logical Shift
• A logical shift is one that transfers 0 through the serial input.
• We will adopt the symbols shl and shr for logical shift-left and shift-right micro
operations.
• Logical shift-left
• Logical shift-Right
• For Example,
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16. Circular Shift
• In a circular shift the serial input is the bit that is shifted out of the other end of the
register.
• We will adopt the symbols cil and cir for logical shift-left and shift-right micro
operations.
• Circular shift-left
• Circular shift-right
• For Example,
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17. ARITHMETIC SHIFT
• An arithmetic shift is meant for signed binary numbers (integer)
• An arithmetic left shift multiplies a signed number by two
• An arithmetic right shift divides a signed number by two
• Sign bit : 0 for positive and 1 for negative
• The main distinction of an arithmetic shift is that it must keep the sign of the
number the same as it performs the multiplication or division.
A right arithmetic shift operation:
A left arithmetic shift operation:
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18. ARITHMETIC SHIFT
• An left arithmetic shift operation must be checked for the overflow.
• In a RTL, the following notation is used
• ashl for an arithmetic shift left
• ashr for an arithmetic shift right
For Example:
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19. Hardware Implementation
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20. Arithmetic Logic Shift Unit
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21. Topics to be covered in next session 5
• Basic computer organization and design
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Thank you!!!