Lect3 organization 2
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This document discusses logic microoperations which specify binary operations for strings of bits stored in registers. It provides examples of selective set, selective complement, selective clear, mask, and insert operations. These logic microoperations are useful for manipulating individual bits or portions of words stored in registers. The document concludes with two assignment questions involving designing a circuit to perform logic operations on a two bit word and using logic microoperations to change the value stored in a register.
Lect3 organization 2
- 1. 10/26/2014 1 Computer Organization Instructors : Dr. Abdul Raouf Khan Mr.Marwan El-Haj Logic Microoperations Logic Microoperations specify binary operations for strings of bits stored in registers. Each bit is considered separately . For example EX-OR operation is symbolized by P : R1 R1 R2 it means, if P=1, EXOR operation of individual bits of R1 and R2 are executed and the result is placed in R1
- 2. 10/26/2014 2 List of Logic Microoperations Hardware implementation of Logic Microoperations
- 3. 10/26/2014 3 Applications Logic Microoperations are very useful for manipulating individual bits or portions of word stored in a register. 1) Selective Set The selective set operation sets to 1 the bits in register A, where there are corresponding 1’s in register B 1 0 1 0 A (before) 1 1 0 0 B (logic operand) ------------------- 1 1 1 0 A ( after ) ( Logic OR)
- 4. 10/26/2014 4 2) Selective Complement The selective Complement operation complements bits in register A, where there are corresponding 1’s in register B 1 0 1 0 A (before) 1 1 0 0 B (logic operand) ------------------- 0 1 1 0 A ( after ) ( Logic XOR) 3) Selective Clear The selective Clear operation clears to 0 the bits in register A, only where there are corresponding 1’s in register B 1 0 1 0 A (before) 1 1 0 0 B (logic operand) ------------------- 0 0 1 0 A ( after ) ( Logic AB”)
- 5. 10/26/2014 5 4) Mask operation The bits in register A are cleared only where there are corresponding 0’s in register B 1 0 1 0 A (before) 1 1 0 0 B (logic operand) ------------------- 1 0 0 0 A ( after ) ( Logic AND) 5) Insert operation Inserts a new value into a group of bits This is done by first masking the bits then ORing them with the required value 0 1 1 0 1 0 1 0 A (before) 0 0 0 0 1 1 1 1 B (mask unwanted bits) ------------------- 0 0 0 0 1 0 1 0 A ( after masking)
- 6. 10/26/2014 6 5) Insert operation (contd ) And Insert a new value 0 0 0 0 1 0 1 0 A ( after masking) 1 0 0 1 0 0 0 0 B (insert bits) ------------------- 1 0 0 1 1 0 1 0 A ( after insertion) The clear operation compares the results 1 0 1 0 A 1 0 1 0 B ------------------- 0 0 0 0 A A B Assignment 1. Design a digital circuit that performs the four logic operations of EXOR, EXNOR, NOR and NAND. Use two selection lines. Show the logic diagram of two stages. ( for two bit word) 2. Register A holds the 8 – bit binary 11011001. Determine the B operand and logic microoperation to be performed in order to change the value in A to a) 01101101 b) 11111101