CODEWITHSUNDEEP
assemblyx86
user379888
user379888

Reputation:

Fixed Port Addressing

I am learning Fixed Port Addressing. The lecture says that its for 8 bits transfer. There were two examples given in it,

Now the second one takes data from register AX which is a 16 bit register. Was it holding a 8 bit address or would it be transferred from a 16 bit address into a 8 bit address?

Upvotes: 0

Views: 836

Answers (1)

Gunther Piez
Gunther Piez

Reputation: 30439

out 6ah, ax will write both bytes of ax to the 16 bit I/O port at 0x6a. A 16 bit port consists of two consecutive 8 bit ports.

That is, it will write al to 0x6a and ah to 0x6b.

See Intel® 64 and IA-32 Architectures Software Developer's Manual Volume 1: Basic Architecture chapter 14.

Upvotes: 4

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