Machine Language - Computer Organization and Design - Lecture Slides, Slides of Computer Aided Design (CAD)

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Machine Language

Apps O/S Arch mArch Logic Digital Analog Devices Physics

Assembly Language  Computer?

• A computer, at its most basic level, needs instruction using a set of bits.
• How do we translate concepts such as “add” into a language the computer understands (machine code)?

Instruction Formats

• In every architecture, there is a set of basic formats that most of their instructions follow.
• In LC2K7, for example:
  • R-type instructions (Register type – and, nand)
  • I-type instructions (Immediate type – lw, sw, beq)

Instruction Encodings

• In order to construct these instructions, we need to translate the information in an assembly statement.
• Opcode : encoded as special codes for each operation
  • add (000), nand (001), lw (010), sw (011), beq (100), jalr (101), halt (110), noop (111)
• Register Values : Just encode the register number
  • r2 = 010 , etc.
• Immediate Values : Just encode the value
  • remember to fill up the allotted bits!

Encoding Example

lw 5 2 -

Instruction Encoding Regularity

• Instruction set architecture also defines the mapping of assembly instructions to machine code add 1 2 3

Encoding – Your Turn, part II

• Compute the encoding (give the hex) for:
  • beq 3 4 top (opcode for beq is 100)
  • The beq is on line 217
  • The label top appears on line 222