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Jikjk 24.08.2019
 Jikjk Essay

Midterm 2 Report

• Highest: 75

• Least expensive: 45

• Average: 83

1

Part 7

Input/Output

Input/Output Concerns

• Wide array of peripherals

– Delivering several amounts of data

– At different rates of speed

– In different formats

• Slower than CPU and RAM

• Need I/O modules

Input/Output Module

Input/Output Module

• Interface to CPU and Memory

• Interface to a single or more

peripherals

Generic Type of I/O Module

I/O Module Function

Control & Timing

CENTRAL PROCESSING UNIT Communication

Device Communication

Data Buffering

Mistake Detection

I/O Module Plan

I/O Methods

• CENTRAL PROCESSING UNIT checks I/O module device

status

• I/O component returns position

• In the event that ready, PROCESSOR requests info

transfer

• I/O module gets info from device

• I/O module transfers data to CPU

Input/Output Techniques

Insight Output

Tactics

• Programmed

• Disrupt driven

• Direct Memory Access (DMA)

Programmed

Input/Output

Programmed I/O

• PROCESSOR has immediate control over I/O

– Sensing status

– Read/write orders

– Shifting data

• CPU is waiting for I/O module to

complete procedure

• Waste materials CPU time

Programmed I/O - depth

PROCESSOR requests I/O operation

I/O module executes operation

I/O module models status portions

CPU inspections status portions periodically

I/O module will not inform CENTRAL PROCESSING UNIT

directly

• I/O component does not disrupt CPU

• CPU may possibly wait or perhaps come back afterwards

Example

• To increase efficiency for programmed I/O, the

software could be written so that the processor

routinely checks the status of the device. In the event

the device is usually not prepared, the processor can

bounce to various other tasks. Following some timed interval,

the processor returns to check position

again.

• Consider the above scheme to get outputting info

one personality at a time into a printer that

operates by 10 characters per second. What

could happen if the status quo is searched every

200ms?

15

I/O Commands

• CPU concerns address

– Identifies component (if #device > 1 per

module)

• CENTRAL PROCESSING UNIT issues control

– Control - telling module how to proceed

• elizabeth. g. spin up drive

– Test - check status

• e. g. power? Error?

– Read/Write

• Component transfers data via

buffer from/to gadget

Addressing I/O Devices

• Under designed I/O info

transfer is extremely like recollection

access (CPU viewpoint)

• Each unit given one of a kind identifier

• CPU commands contain designation

(address)

I/O Mapping

• Memory mapped I/O

– Devices and memory reveal an address

space

– I/O looks just like memory read/write

– No unique commands to get I/O

• Large selection of memory access

commands offered

• Remote I/O

– Separate address spaces

– Need I/O or memory select lines

– Exceptional commands pertaining to I/O

• Limited established

Memory Planned and Remote I/O

Disrupt Driven

Input/Output

Interrupt Influenced I/O

• Overcomes CPU waiting

• No repeated CPU checking of

unit

• I/O module interrupts when all set

Interrupt Driven I/O

Standard Operation

• CPU issues read control

• I/O module gets data coming from

peripheral while CPU does other

job

• I/O module interrupts CPU

• CPU needs data

• I/O component transfers info

Example

• A particular system is controlled simply by an

owner through directions entered

coming from a key pad. The average number

of orders entered within an 8-hour

period is 60.

• Suppose the processor scans the

keyboard every single 100ms with

programmed I/O. How many times will

the keyboard be checked out in an-8-hour

period?

twenty-three

Answer

• The processor scans the keyboard 10

instances per second. In 8 hours, the

number of occasions the keyboard is definitely

scanned can be 10 × 60 × 60 × 8 sama dengan

288, 1000.

24

Case (cont'd)

• For the same example, by what small fraction

would the amount of processor appointments to

the keyboard be lowered if interruptdriven I/O had been used?

twenty-five

Example (cont'd)

• For the similar example, with what fraction

would the number of cpu visits to

the keyboard end up being reduced if perhaps interruptdriven I/O were applied?

• Just 60 trips would be...

UNIT 15 Assignment you Essay

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