Functional components of a computer Main memory CPU

Main memory CPU Arithmetic/Logic Unit ( ALU ) Control Unit Register(s)

Registers • The special storage devices in the CPU that CPU uses over and

Registers Examples of special purpose registers : – PC ( Program Counter ) –

Main Memory CPU MDR R 0 R 1 IR PC MAR RN Control unit

Main Memory Operations Memory read operation – Transfers the content of a specific main

Main Memory Operations Memory write operation – Transfers a word of information from the

Memory 300 301 302 940 941 1940 5941 2941 : : 0003 0002 CPU

Memory 300 301 302 940 941 1940 5941 2941 : : 0003 0002 16

Memory 300 301 302 940 941 1940 5941 2941 : : 0003 0005 16

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Functional components of a computer

Main memory CPU Arithmetic/Logic Unit ( ALU ) Control Unit Register(s)

Registers • The special storage devices in the CPU that CPU uses over and over again for execution of stored-program instructions. • There are two types of registers : – General purpose registers – Special purpose registers

Registers Examples of special purpose registers : – PC ( Program Counter ) – IR ( Instruction Register ) – MAR ( Memory Address Register ) – MDR or MBR ( Memory Data Register or Memory Buffer Register ) – PSW ( Program Status Word ) – etc.

Main Memory CPU MDR R 0 R 1 IR PC MAR RN Control unit ALU Data bus Control bus Address bus

Main Memory Operations Memory read operation – Transfers the content of a specific main memory location to the CPU. – The content of the main memory location remains (unchanged).

Main Memory Operations Memory write operation – Transfers a word of information from the CPU to a specific main memory location. – Destroys the former content of the main memory location. Memory access time – The time it takes to perform a memory read or a memory write operation.

Memory 300 301 302 940 941 1940 5941 2941 : : 0003 0002 CPU Registers 300 PC 1940 AC IR Step 1 16 bits • PC (Program Counter) �� (=30016) • Processor �� (194016) �� 30016 �� IR • PC �� 1 ��

Memory 300 301 302 940 941 1940 5941 2941 : : 0003 0002 CPU Registers 3 0 1 PC 0003 1940 AC IR 00012 = 116 16 bits Step 2 • Processor �� (194016) �� IR Ø 4 bits �� load �� 94016

Memory 300 301 302 940 941 1940 5941 2941 : : 0003 0002 CPU Registers 3 0 1 PC 0003 5941 16 bits AC IR Step 3 • �� (594116) �� 30116 �� IR • PC �� 1 ��

Memory 300 301 302 940 941 1940 5941 2941 : : 0003 0002 16 bits • �� (594116 ) CPU Registers 3 0 2 PC 0005 5941 AC IR 3+2 = 5 01012 = 516 Step 4 Ø 516 = 01012 �� 94116�� AC

Memory 300 301 302 940 941 1940 5941 2941 : : 0003 0002 CPU Registers 3 0 2 PC 0005 2941 AC IR Step 5 16 bits • �� (294116) �� 30216 �� IR • PC �� 1 ��

Memory 300 301 302 940 941 1940 5941 2941 : : 0003 0005 16 bits • �� (294116 ) CPU Registers 3 0 3 PC 0005 2941 00102 = 216 AC IR Step 6 Ø 216 = 00102 �� AC �� 94116