The Little Man Computer CSE 1540 Computer Use in the Natural Sciences
Instruction cycle (fetch) 1. Read address from Location Counter; 2. Walk to address CSE 1540 3. Read content Computer Use in the Natural Sciences
Instruction cycle (execute LOAD 1/2) 1. Go to mailbox specified by instruction CSE 1540 2. Read content Computer Use in the Natural Sciences
Instruction cycle (execute LOAD 2/2) 3. Go to calculator and punch content CSE 1540 4. Increment LC Computer Use in the Natural Sciences
System Block Diagram CPU Highest Address ALU Input/output interface Memory Control unit Program counter CSE 1540 Computer Use in the Natural Sciences Lowest Address
The Little Man Computer CSE 1540 Computer Use in the Natural Sciences
Generic CPU With Registers Program Counter ( PC ) Instruction Register ( IR ) Memory Address Register ( MAR ) Memory Data Register ( MDR ) Accumulator ( A or Acc ) CSE 1540 Computer Use in the Natural Sciences Memory
Memory Unit Memory cell bit 0 bit 1 bit n - 1 0 1 2 3 4 Address decoder Memory address register n bits 0 1 2 m-1 Memory data register 2 n-1 m bits p. 160 CSE 1540 Computer Use in the Natural Sciences
MAR-MDR example CSE 1540 Computer Use in the Natural Sciences
A visual analogy for memory CSE 1540 Computer Use in the Natural Sciences