Why memory mapped io

Picture source : IO Devices. To access a hardware device, simply read or write to those 'special' addresses using the normal memory access instructions. The disadvantage to this method is that the entire address bus must be fully decoded for every device.

For example, a machine with a bit address bus would require logic gates to resolve the state of all 32 address lines to properly decode the specific address of any device.

This increases the cost of adding hardware to the machine. This is usually accomplished by having a different set of signal lines to indicate a memory access versus a port access. Nate Symer Nate Symer 2, 1 1 gold badge 17 17 silver badges 25 25 bronze badges.

What do you suggest as an alternative? Add a comment. Active Oldest Votes. Improve this answer. Brendan Brendan Sign up or log in Sign up using Google. Sign up using Facebook.

Sign up using Email and Password. Post as a guest Name. Email Required, but never shown. The Overflow Blog. Podcast Explaining the semiconductor shortage, and how it might end. Does ES6 make JavaScript frameworks obsolete? Featured on Meta. Now live: A fully responsive profile. Related The same is the case with the memory write operation. The required chip select signals in this case are generated by an individual decoding unit.

Your email address will not be published. Save my name, email, and website in this browser for the next time I comment. Thus, it is suitable for systems where less memory requirement exists.