mar18ce.docx

ASSEMBLY LANGUAGE  MICROPROCESSOR WITHOUT INTERLOCKED PIPELINE STAGES (MIPS)  Intro to Machine Code o Type of REDUCED INSTRUCTION SET COMPUTER (RISC) architecture o Now that we have a processor, operations are performed by: o Provides a set of simple and fast instructions  The instruction register, decoding each instruction according to  Compiler translates instructions into 32-bit instructions for the opcode in the first 6 bits instruction memory  The control unit sending a sequence of signals to the rest of the  Complex instructions (multiplication) are built out of simple processor, according to the opcode value passed in from the ones by the compiler and assembler o Only question remaining: o MIPS is REGISTER-TO-REGISTER  Hwere do these instructions come from?  Every operation operates on data in registers  How are they provided to the instruction memory? o MIPS provides 32 registers, several have secial values  Assembly language  Register 0 ($zero): value 0 o Each processor type has its own language for representing 32-bit  always 0; can’t write into this register, only read instructions as user-level code words  Register 1 ($st): reserved for the assembler o Ex. C = A + B  Store A in $t1, B in $t2, C in $t3  Register 2 – 3 ($v0, $v1): return values  In Assembly Language instruction:  Register 4 – 7 ($a0 – a3): function arguments add $t3, $t1, $t2  Register 8 – 15, 24, 25($t0 – $t9): temporaries  In Machine Code instruction:  Register 16 – 23 ($s0 – $s7): saved temporaries 000000 01001 01010 01011 XXXXX 100000  Register 28 – 31 ($gp, $sp, $fp, $ra): memory and function  Control Unit signals: support  PCWrite = 0 PCWriteCond = 0  $sp is top of the stack, increments to 0  IorD = X  $ra is the return address, the address of a main program  MemRead = 0, MemWrite = 0  when a subroutine complete, $ra is used to return to  MemtoReg = 0 the main program  IRWrite = 0  $fp is the frame pointer  PCSource = X  $gp is the global pointer  ALUOp = 001 (add) o Also three special registers (PC, HI, LO) that are not directly  ALUSrcA = 1, ALUSrcB = 0 accessible  RegWrite = 1, RegDst = 1 (R-type)  HI and LO are used for multiplication and division, and have  Note: most of the time only one write signal is on special instruction for accessing them o Ex. Add 100 to value in PC and store it back into the PC  MIPS Instructions  Operation used by Assembly to jump o Things to note about MIPS instructions  Instruction is addi, the value 100 in instruction[15-0]  Instructions are written as:  ALUSrcB is from Sign Extend, needed b/c the value  Each instruction is written on its own line 100 in instruction[15-0] is 16-bits, need 32-bits  All instructions are 32-bits (4 bytes) long