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The Little Man Computer. Instruction cycle (fetch). Read address from Location Counter; Walk to address 3. Read content. Instruction cycle (execute LOAD 1/2). 1. Go to mailbox specified by instruction 2. Read content. Instruction cycle (execute LOAD 2/2).
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Instruction cycle (fetch) • Read address from Location Counter; • Walk to address 3. Read content
Instruction cycle (execute LOAD 1/2) 1. Go to mailbox specified by instruction 2. Read content
Instruction cycle (execute LOAD 2/2) 3. Go to calculator and punch content 4. Increment LC
System Block Diagram CPU Highest Address Memory Lowest Address ALU Input/outputinterface Control unit Program counter
Generic CPU With Registers Program Counter ( PC ) Memory Instruction Register ( IR ) Memory Address Register ( MAR ) Memory Data Register ( MDR ) Accumulator ( A or Acc )
Memory Unit n bits Memory cell bit 0 0 1 2 3 4 2n-1 bit 1 Memory address register Address decoder bit n - 1 0 1 2 m - 1 Memory data register m bits p. 160
