Input/Output. What is I/O?. How we get the CPU to communicate with devices From the computer’s point of view, it’s just 1’s and 0’s Gets interpreted by the device it is sent to (output) Computer interprets data received (input). Devices. What are devices?. Obvious ones… Mouse Keyboard
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What are devices?
A collection of wires which carry data between the CPU, memory and I/O devices
Interface between computer’s bus and I/O device
Device-specific communication link
Actual I/O device
These are the devices that actually do the physical input, output and data storage operations.
Examples: keyboard printer
mouse floppy disk
They do not connect directly to the computer’s bus.
A peripheral is anything connected to the computer except the CPU, memory and power supply
These are the devices that provide interfaces between the computer’s buses and the peripherals. In general, they do the following:
I/O ports can be classified according to the type of interface they implement. The two commonest are:-
(e.g. to a printer)
(e.g. to a VDU or modem)
Think: pins on a printer cable before USB!
RDY: sender says data is ready
ACK: receiver acknowledges receipt
Receiver acknowledges receipt
Sender stops asserting data ready
Receiver acknowledges transmission over
Sender asserts data ready
Sender puts data on lines
The serializer takes the (8 bits of) input, and translates them to a single stream of data
It tells the CPU (status and control register) when data transmission is complete
It reads from the status & control register information about how to format the data, and what speed to send it