Block Diagram of an I/O Module |
Figure
provides a general block diagram of an I/O module. The module connects to the
rest of the computer through a set of signal lines (e.g. system bus lines).
Data transferred to and from the module are buffered in one or more data
registers. There may also be one or more status registers that provide current
status information. A status register may also function as a control register,
to accept detailed control information from the processor. The logic within the
module interacts with the processor via a set of control lines. Each I/O module
has a unique address or, if it controls more than one external device, a unique
set of addresses. Finally, the I/O module contains logic specific to the
interface with each device that it controls. An I/O module functions to allow
the processor to view a wide range of devices in a simple minded way.
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