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Instruction Cycle

The document outlines the design and operation of a basic computer, detailing components such as the memory unit, registers, flip-flops, and control logic. It includes instructions for executing specific operations and questions related to register values and instruction cycles. The document serves as a guide for understanding register reference instructions and their effects on the computer's state.

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nemojames074
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45 views24 pages

Instruction Cycle

The document outlines the design and operation of a basic computer, detailing components such as the memory unit, registers, flip-flops, and control logic. It includes instructions for executing specific operations and questions related to register values and instruction cycles. The document serves as a guide for understanding register reference instructions and their effects on the computer's state.

Uploaded by

nemojames074
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as PDF, TXT or read online on Scribd
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Instruction Cycle

Register Reference Instructions


Interrupt Cycle
Register Transfer Statements
Design of a Basic Computer

➢ Memory Unit
➢ Nine Registers
➢ Seven Flip-flops : I, S, E, R, IEN, FGI, FGO
➢ Two decoders
➢ Common Bus
➢ Control Logic Gates
➢ Adder and Logic Unit
Signals to Control

➢ Inputs of nine registers


➢ Read and Write inputs of memory
➢ Set, Clear and Complement the flags
➢ Select a register for bus
➢ Adder and Logic Circuit
Control Logic Circuit
Control of Flip-flops
Control of Common Bus
Design of Accumulator Logic
Questions
1. The content of AC in the basic computer is hexadecimal A937 and the initial value of E is 1.
Determine the contents of AC, E, PC, AR, and IR in hexadecimal after the execution of CLA
instruction. Repeat 11 more times, starting from each one of the following of the register-
reference instructions. The initial values of PC is hexadecimal 021.
2. The content of PC in the basic computer is 3AF. The content of AC is 7EC3. The content of
memory at address 32E is 09AC. The content of memory 9AC is 8B9F.
(a) What is the instruction that will be fetched and executed next?
(b) Show the binary operation that will be performed in the AC when the instruction is
executed.
(c) Give the contents of registers PC, AR, DR, AC and IR in hexadecimal and the values of
E, I and the sequence counter SC in binary at the end of the instruction cycle.
3. An 8-bit register contains the binary value 10011100. What is the register value
after arithmetic shift right? Starting from the initial number 10011100, determine
the register value after arithmetic shift left, and state whether there is an overflow.

4.An instruction at address 021 in the basic computer has I=0, an operation code
of the AND instruction, and an address part equal to 083. The memory word at
address 083 contains the operand B8F2 and the content of AC is A937. Go over
the instruction cycle and determine the contents of the following registers at the
end of the execute cycle: PC, AR, DR, IR and AC. Repeat the cycle for other
memory reference instructions

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