计算机组织与结构课件全分单元Ch10章节幻灯片.ppt

5 7 8 9 10 12 13 14 15 18 25 William Stallings Computer Organization and Architecture6th Edition Chapter 10 Instruction Sets: 指令集 Characteristics and Functions 汇编编码表示 What is an instruction set? The complete collection of instructions that are understood by a CPU Machine Code Binary Usually represented by assembly codes Elements(成分) of an Instruction Operation code (Op code) 操作码 Do this Source Operand reference 源操作数的信息 To this Result Operand reference目标操作数的信息 Put the answer here Next Instruction Reference下一条指令的信息 When you have done that, do this... Page 330 Where have all the Operands gone? Main memory (or virtual memory or cache) CPU register I/O device Page 331 Instruction Cycle State Diagram Page 331 or Page57 Fetch cycle Execute cycle Instruction Representation In machine code each instruction has a unique bit pattern For human consumption (well, programmers anyway) a symbolic representation is used 用符号表示 e.g. ADD, SUB, LOAD Operands can also be represented in this way ADD A,B (A and B are symbolic address) Page 332 Simple Instruction Format Page 332 English word Symbolic Symbolic e.g. A instruction: (513)+(514) —X X Y Add X, Y; —— Assembly Instruction Number of Addresses (a) 4 addresses: Operand1, Operand2, Result, Address(next instruction) Be extremely rare, because of PC. 3 addresses Operand 1, Operand 2, Result a ? b + c;(a,b and c are symbolic address) May be a forth - next instruction (usually implicit) Page 334 Example(1) Turn to page 335 Y=(A-B) ?(C+D x E) Three-address instructions —SUB Y, A, B; Y?A-B —MPY T, D, E; T?D x E —ADD T, T, C; T?T+C —DIV Y, Y, T; Y?Y ? T Total:four instructions page 335 Number of Addresses (b) 2 addresses One address doubles as operand and result a = a + b Reduces length of instruction Requires some extra work Temporary storage to hold some results Example(2) Turn to page 335 Y=(A-B) ?(C+D x E) T