<
architecture> The use of the same instructions and
bus to
communicate with both
main memory and
input/output
devices. This is in contrast to processors that have a
separate I/O
bus and special instructions to access it.
The I/O devices are addressed at certain reserved address
ranges on the main
memory bus. These addresses cannot
therefore be used for
RAM.
Motorola and
Mostec
architectures, among others, use
memory mapped I/O.
Video cards and other cards with on-board
memory might be
accessed in this way though the term applies not just to
devices containing
memory but to any device connected to the
memory bus. Accessing the devices usually consists of reading
and writing certain built-in
registers though sometimes the
mere presence of a particular address can trigger the device.
(1997-04-14)