30-10-2012, 04:02 PM
Instruction Formats
Instruction Formats.docx (Size: 12.46 KB / Downloads: 24)
• It is the function of the control unit within the CPU to interpret each instruction code
• The bits of the instruction are divided into groups called fields
• The most common fields are:
Operation code
o Address field – memory address or a processor register
o Mode field – specifies the way the operand or effective address is determined
• A register address is a binary number of k bits that defines one of 2k registers in the CPU
• The instructions may have several different lengths containing varying number of addresses
• The number of address fields in the instruction format of a computer depends on the internal organization of its registers
• Most computers fall into one of the three following organizations:
o Single accumulator organization
o General register organization
o Stack organization