ch11-IO-polling

ch11-IO-polling - I/O polling EE 3750 2 Instructions for...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: I/O polling EE 3750 2 Instructions for input and output IN AL, source (byte) IN AX, source (word) source is a port address source may be DX: variable address up to 16-bits long or an 8-bit constant (fixed address) OUT dest, AL (byte) OUT dest, AX (word) dest is a port address; may be DX or an 8-bit constant Example instructions: IN AX, 4DH IN AL, DX OUT DX, AX 3 Polling program-controlled I/O Processor examines (polls) the status of an interface and performs an I/O operation when the status of the interface indicates that it has data to be input or that its data-out buffer register is ready to receive data from the processor. Figure below shows program- controlled input 4 Example 1 Output one word of data by program-controlled I/O from buffer (variable) WHITE. Let 20H be the data port address (word-size), 22H be the status port address (byte-size), and let bit 1 be the ready bit....
View Full Document

This note was uploaded on 01/25/2012 for the course EE 3750 taught by Professor Desouza during the Fall '08 term at LSU.

Page1 / 5

ch11-IO-polling - I/O polling EE 3750 2 Instructions for...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online