port address : Computer Hardware Buyers’ Glossary

by Roedy Green ©1997-2008 Canadian Mind Products
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port address: Now that plug & play works reasonably well, the average user no longer needs to understand port addresses. Basically the idea is that every I/O device (e.g. disk controller, video controller, mouse controller etc.) gets assigned an ID number (or numbers) in the range 0:65536 (0000:ffff hex). The CPU can read or write these locations much the way it accesses RAM to control the device, read data from it, or write data to it. It is mandatory that no two devices are assigned the same number. Plug & Play handles automatically assigning unique port addresses to all your devices. In the old days and today with legacy devices, it is up to you to assign the port addresses and guarantee uniqueness, often by setting jumpers or running special configuration firmware.
firmware
IRQ
jumper
Plug & Play
port

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