Input & Output ( function )

Input and Output

I/O devices have three characterized which are

-          Behaviour : input, output, and storage

-          Partner : Human or machine

-          Data rate : bytes/sec, transfers/sec

Input devices – keyboard, mouse, scanner…

Output devices – monitor, printer, speaker…

Function of I/O modules

Input/ Output Module Structure

There are five function on I/O modules which are control & timing, CPU communicating, device communication, data buffering and error detection.

    Control and Timing

It is for control multiple devices all communicating on the same channel.

a.       CPU checks I/O module device status of attached device

b.      I/O module check the status

c.       If ready, CPU requests data transfer

d.      I/O module gets data from device and transfers data to CPU

e.       Variations for output, DMA.

f.       Rate of transmission from device to CPU or vice-versa

I/O System Characteristics

Dependability is important because it is helping for particularly of storage device.

They performance is based on the latency (the time response), throughput (bandwidth of decive), desktops & embedded systems (constant the response time and diversity of devices), and servers (constant the throughput and expandability of devices)

CPU Communication

1.      Processor communication

• Command decoding: CPU sent a command as signals on the control bus for I/O module to work.

• Data: Exchanged between the CPU and I/O module

• Status reporting: Status signals BUSY and READY are reporting to CPU because peripherals are slow

• Address recognition: I/O module will connected a unique address for each peripheral that it controls.

2.      I/O module communication

• Device communication: These are includes commands, status information, and data transfer.

• Data buffering: data comes from main memory in rapid burst and buffered by the I/O module sent to the device at the device’s rate. It is essential function to overcome the speed mismatch other.

• Error detection: For reporting errors to the processor such as bad data.

Dependability

 Service accomplishment will make sure the service delivered as specified. If it is failure of a component and it may lead to system failure, it will send to service interrupt department to deviation again from specified service for restoration. This step will repeat until restoration success it.

Device Communication

It is specific for each input and output device.

Data Buffering

It is define the speed by different device are using. Usually device is oders of magnitude slower, the I/O module will buffer data to keep tie up from CPU's bus with slow read or write.

Error Detection

For disturbing require for checking error to module.

Dependability Measure

It will based on few characteristics to determine it.

1.      Reliability : MTTF, (mean time to failure) to checking the devices.

2.      Service interruption : MTTR,(mean time to repair) to repair the error devices.

3.      Mean time between failures, MTBF = MTTF + MTTR , for repeat the step above until it get successful restore.

4.      Availability : MTTF/ ( MTTF+MTTR )

5.      Improving Availability :  Increase the MTTF, fault avoidance, fault tolenrance and fault forecasting. This all can help to increasing the MTTF value. Besides that, we also can reduce MTTR, the less repair mean less error are find on the devices. SO that we must improved tool and processes for diagnosis and repair to shorter the time.

Bus signals and Synchronization

They are have relation between each other to help to perform more better in the process pass by input and output devices.

·         For data line

They will carry address and data to make it become a multiplexed or separate it nicely to avoid mismatch or error connection.

·         Control line

They will indicate the data type for make sure the transfer are able to detecting that data and synchronize the transaction.

·         Synchronous

Uses a bus clock to cycle the process.

·         Asynchronous

For the control which are lock must getting request/acknowledge for control lines to handshaking.

Interconnecting Components

-          The components are require to interconnecting is between CPU processor, memory, and I/O controller.

-          Bus is sharing the communication channel. The parallel set of wires bus are data and synchronization transfer data. Bus also cause to bottleneck in the process.

-          Performance are limited by physical factors such the wire length, number of connection. These all is the once of the cause to affect the performance.

-          More recent alternative is able to help to increase the high speed serial connection with the switch such network or bookmark function.

Bus types

There are two type which are processor – memory buses and I/O buses.

a.       Processor – memory buses

The wire length is short and high speed. The design between this two component is match to memory organization.

b.      I/O buses

The wire length is longer and it also allow multiple connection happen. Therefore the speed is short compare with processor – memory buses. It is specified by standard for interoperability process. At the end, it also will connect back to processor – memory bus through a bridge to complete it.

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