memory mapped I/O
<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)
Nearby terms:
memory location « memory management « Memory
Management Unit « memory mapped I/O » memory
protection » memory smash » Memory Type Range
Registers
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