I/O module function and mapping

I/O module function:
Control and Timing; this coordinates the flow of traffic between external devices and internal resources.
CPU Communication; this involves command decoding in I/O module, data exchange through data bus, etc.
Device Communication; involves commands, status information and data.
Data Buffering; the data are buffered in the I/O module and then sent to the peripheral device at its data rate.
Error Detection; this is for reporting errors to the processor.

I/O Module Diagram

Thus, I/O Module takes most of processing burden and becomes a high-level interface to processor also refer to as I/O channel, I/O controller, device controller, etc.

I/O Mapping:
This is when a processor, memory and I/O share a common bus. There are two types of interfacing and they include;
1.   Memory mapped I/O;
o  Devices and memory share an address space
o  I/O looks just like memory read and write
o  No special commands for I/O
2.   Isolated I/O;
o  Separate address spaces
o  Need I/O or memory select lines
o  Needs special commands for I/O