remaining 12 bit as part of operation code so total number of instruction can

Remaining 12 bit as part of operation code so total

This preview shows page 19 - 25 out of 49 pages.

remaining 12 bit as part of operation code so total number of instruction can exceed 8 Infact total no. of instructions chosen for basic computer is 25
Image of page 19

Subscribe to view the full document.

Basic Computer Organization and Design 20 CSE 211 Basic Computer Instructions AND 0xxx 8xxx AND memory word to AC ADD 1xxx 9xxx Add memory word to AC LDA 2xxx Axxx Load AC from memory STA 3xxx Bxxx Store content of AC into memory BUN 4xxx Cxxx Branch unconditionally BSA 5xxx Dxxx Branch and save return address ISZ 6xxx Exxx Increment and skip if zero CLA 7800 Clear AC CLE 7400 Clear E CMA 7200 Complement AC CME 7100 Complement E CIR 7080 Circulate right AC and E CIL 7040 Circulate left AC and E INC 7020 Increment AC SPA 7010 Skip next instr. if AC is positive SNA 7008 Skip next instr. if AC is negative SZA 7004 Skip next instr. if AC is zero SZE 7002 Skip next instr. if E is zero HLT 7001 Halt computer INP F800 Input character to AC OUT F400 Output character from AC SKI F200 Skip on input flag SKO F100 Skip on output flag ION F080 Interrupt on IOF F040 Interrupt off Hex Code Symbol I = 0 I = 1 Description
Image of page 20
Basic Computer Organization and Design 21 CSE 211 Instruction Set Completeness The set of instructions are said to be complete if computer includes a sufficient number of instruction in each of the following categories : A computer should have a set of instructions so that the user can construct machine language programs to evaluate any function that is known to be computable. Functional Instructions - Arithmetic, logic, and shift instructions - ADD, CMA, INC, CIR, CIL, AND, CMA, CLA Transfer Instructions - Data transfers between the main memory and the processor registers - LDA, STA Control Instructions - Program sequencing and control - BUN, BSA, ISZ Input/output Instructions - Input and output - INP, OUT
Image of page 21

Subscribe to view the full document.

Basic Computer Organization and Design 22 CSE 211 Control Unit Control unit (CU) of a processor translates from machine instructions to the control signals for the microoperations that implement them Control units are implemented in one of two ways Hardwired Control CU is made up of sequential and combinational circuits to generate the control signals Advantage : optimized to provide fast mode of operations Disadvantage : requires changes in wiring if design has been modified Microprogrammed Control A control memory on the processor contains microprograms that activate the necessary control signals We will consider a hardwired implementation of the control unit for the Basic Computer
Image of page 22
Basic Computer Orgsnization and Design 23 CSE 211 Timing and Control Control unit of Basic Computer Instruction register (IR) 15 14 13 12 11 - 0 3 x 8 decoder 7 6 5 4 3 2 1 0 I D 0 15 14 . . . . 2 1 0 4 x 16 decoder 4-bit sequence counter (SC) Increment (INR) Clear (CLR) Clock Other inputs Control signals D T T 7 15 0 Combinational Control logic
Image of page 23

Subscribe to view the full document.

Basic Computer Orgsnization and Design 24 CSE 211 Timing Signals Clock T0 T1 T2 T3 T4 T0 T0 T1 T2 T3 T4 D3 CLR SC - Generated by 4-bit sequence counter and 4 16 decoder - The SC can be incremented or cleared.
Image of page 24
Image of page 25
  • Summer '17

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern

Ask Expert Tutors You can ask 0 bonus questions You can ask 0 questions (0 expire soon) You can ask 0 questions (will expire )
Answers in as fast as 15 minutes