ch4-mcLang

ch4-mcLang - Machine language EE 3750 Instruction Native...

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Machine language EE 3750 2 Instruction format Native binary code that the microprocessor uses as its instructions to control its operation. Their lengths vary from 1 to 13 bytes (1 to 6 bytes for the 8086). The instructions for the 8086 have the format shown below. Brey text has formats for individual instructions in Appendix B. Opcode MOD-REG-R/M Displacement Immediate 1 to 2 bytes 0 to 1 byte 0 to 2 bytes 0 to 2 bytes
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3 Opcode byte Opcode selects the operation to be performed by the microprocessor. The remaining bits indicate: D – direction of flow of information (can also view as destination bit): » D=0: from REG to R/M (that is, REG is source); » D=1: from R/M to REG (that is, REG is destination). W – size of data: » W=0: byte; » W=1: word (can be doubleword in 80386 and later). S - sign-extension » SW = 00: 8-bit operation » SW = 01: 16-bit operation, 16-bit operand » SW = 11: 16-bit operation, sign-extended 8-bit immediate operand D or S
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This note was uploaded on 01/25/2012 for the course EE 3750 taught by Professor Desouza during the Fall '08 term at LSU.

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ch4-mcLang - Machine language EE 3750 Instruction Native...

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