Trouble with opcodes

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Karlosoft
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Trouble with opcodes

Post by Karlosoft »

Hi! A very easy and fast question: what is the complete hex code of mov Ev, Iv where Ev=AX and Iv is 12? Trying with nasm is completely not-usefull because it use the opcode mov AX, Iv that doesn't require MOD R/M byte.
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Gigasoft
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Re: Trouble with opcodes

Post by Gigasoft »

C7 C0 12 00
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Karlosoft
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Re: Trouble with opcodes

Post by Karlosoft »

Thank you! The mem bits are empty?
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Gigasoft
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Re: Trouble with opcodes

Post by Gigasoft »

Well, it's the register bits that are ignored. The memory bits are 11xxx000, meaning AX.
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Re: Trouble with opcodes

Post by thepowersgang »

Karlosoft wrote:Hi! A very easy and fast question: what is the complete hex code of mov Ev, Iv where Ev=AX and Iv is 12? Trying with nasm is completely not-usefull because it use the opcode mov AX, Iv that doesn't require MOD R/M byte.
For future reference, look at the end of Volume 2A of Intel Manuals for the mov instruction.
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