A piece of equipment(mouse, printer,scanner,etc) attached to a computer to perform tasks that a computer cannot do itself is called peripherals.Such as plotters, printers,scanners, digitizers, graphics displays, modems, scanners and so on.forth that support and enhance the functioning of a computer.
Interfacing is a technique by which peripherals devices can be connected to the computer. That is, computer interfacing means connecting different devices to the computer and being able to to control or read the status of these devices.There are many way to achieve computer interfacing.
1.Interfacing by making our own computer interface.
2.Interface via the existing ports in your computers.
The roles of Computer peripherals :
Generally peripherals device connected to th central processor.Different roles of peripherals are used to organized compurter peripherals-
1. Payroll and account systems
2.Retail stock control & distribution
4.General information system
7.Computer Aided design
8.Scientific calculation to implement microprocessor.
The difference between asybchronous transmission and synchronous transmission :
Asybchronous transmission Synchronous transmission 1.In asynchronuous transmission, each information character is individually synchronized. Each character/byte is formed with a start bits(0) at the beginning & one or more stop bits(1) at the end. These may be a gap i.e.unpredictable time interval between characters . 1.In synchronuous transmission, a block of bits referred to as a frame is transmitted without start & stop codes & without gap between bytes. The block i.e. frame consist may bits in length.Each frame the starting & ending flag . 2.Occurs farming error. 2.Doesn't occur any framing error. 3.Asynchronuous transmission is simple & cheap . 3.Synchronuous transmission is cost. 4.This systems requires an overhead of two to three bit per character. 4.This systems requires less bit per character. 5.Slower than synchronuous transmission. 5.Faster than asynchronuous transmission.
The difference between status check and interrupt I/O technique :
status check/Programmed I/O interrupt I/O technique It is a technique in which I/O occurs under the direct & continuous control of the program requesting the I/O operation . 1.It is a technique in which a program issues an I/O command & then continuous to execute, until it is interrup by the I/On hardware to signal the end of th I/O operation . 2.Programmed I/O is less efficient than interrupt I/O technique. 2.It is more efficient than programmed I/O technique because it eliminates needless waiting. 3.Status I/O consumes a less of processor time. 3.Interrupt I/O still consumes a lot of processor time, because every word of data that goes from memory to module or from I/O module to memory must pass through the processor.
The difference between Memory mapped I/O and Periphera or standard mapped I/O :
Memory mapped I/O Periphera or standard mapped I/O 1.Memory related instructions are used to transfer data E.g LDA, STA. 1.I/O related instructions are used to transfer data E.g IN, OUT . 2.16-bit. 2.8-bit. 3.between any register & I/O. 3.Only between I/O & accumulator. 4.Not need is used latch. 4.A latch is commonly used to interface output device. 5.MEMR/MEMW i.e memory read or memory writes . 5.IOR/IOW i.e Input output write. 6.More h/w needed to decode 16-bit address. 6.Less h/w needed to decode 8-bit address. 7.The memory mapped is shared between I/O and system memory. 7.The I/O map is independent of the memory map. 8.Not need. 8.A tri state buffer is commonly used to interface input device. 9.Arithmatic & logical operations can be directly performed with I/O data. 9.Not available.
Dot matrix :
The dot matrix representation consists of a matrix of dots, in the case of character display usually a 5*7 matrix.For greater clarity, usually with text display, 7*9, 10*4 or greater matrix sizes can be used.Lower case letters can be accommodated by an extra one,two,or three rows for the character tails.
For example : a 5*7 dot matrix typically becomes 5*7 dot matrix for upper and lower case, a 7*9 dot matrix becomes a 7*12 dot matrix.Foreign language symbols can be accomodated with a dot matrix.
For Example : Arabic symbols can be represented.
The Display device.Name the common display devices :
A computer is capable of sending its output to a wide variety of devices, many of which are designed for special purpose.These devices which are capable of producing graphical output are known as the display device(output device).
Common Display devices : The most comonly used computer output devices are -
1.Raster-scan cathody ray tube(CRT),
4.Liquid crystal displays(LCDs),
The advantages of active transducer :
Active transducer are also known as self-generating type transducers. These transducers develop their own voltage or current. The energy required for production of an output signal is obtained from the physical phenomenon being measured.
Advantages of Active transducer :
1. Electrical amplification & attenuation can be easily done.
2.Mass inertia effects are minimized
3.Effects of friction are minimized
4.The output can be indicated & recorded remotely at a distance from the sensing medium.
5.They are inexpensive
6.Simple to operate & are very useful for application where the requirements are not particulaly severe.
Steps are necessary to communicate with peripherals through the 8255A :
1.Determine the addresses of ports A, B and C and of the control register according to the chips select logic and address lines A0 and A1. 2.Write a control word in the control, register. 3.Write I/O instructions to communicate with peripherals through ports A, B and C.
Elements are required for programmable I/O devices :
1.A control register in which the MPU can write an instruction
2.A status register that can be read by the MPU
3.I/O devices or register
5.Chip select logic
6. Bidirectional data bus 7.Handshake signals and interrupt logic.
Handshake signals :
The MPU and peripherals operate at different speeds; therefore, signals are exchanged prior to data transfer between the fast-responding MPU and slow-responding peripherals such as printers and data converters.These signals are called handshake signals.
The advantages and disadvantages of transducer :
Advantages of electrical transducer : The advantages of electrical transducer are as follows-
1.Electrical application & attenuation can be easily done.
2.Mass inertia effects are minimized
3.Effects of friction are minimized.
4.THe output can be indicated & recoreded remotely at a distance from the sensing medium.
5.The electrical or electronic system can be controlled a very small level.
6.They are inexpensive .
7.Simple tio operate & are very useful for application where the requirements are not particularly server.
8.While the frequency response of wire wound potentiometers is limited, the other types of potetiometers are free from, this problem.
9.The electrical is very high.
Disadvantages of transducer :
1.Using linear potemiometer is the they require a large force to move their sliding contacts(wipers).
2.For long time use, sliding contact can be damaged.
The difference between raster scan CRT and random access or vector CRTs Or, make a comparison between vector graphics & raster-scan graphics display system :
Raster scan CRT and random access vector CRTs 1.raster access CRTs do not follow a regular scanning pattern. 1.raster scan CRT follows a regular scanning pattern . 2.random access CRT presents much better animation than a raster-scan CRT. 2.raster scan CRT presents less animation than a random access CRT. 3.Memory requirements are reduced because a coordinate lsit is stored rather than a memory map. 3.Memory requirements can not be reduced in this method. 4.The vector CRT/random access CRT is not able to refresh the line often enough & the display begin to flicker. 4.Able to refresh the line.
The difference between active & passive transducer :
Active transducer Passive transducer 1.Active transducers are also known as self-generating type transducers.These transducer develop their own voltage or current.The energy required for production of an output signal is obtained from the physical phenomenon being measured. 1.Passive transducer operates under energy controlling principles, which makes it necessary to use an external electrical source with them. They depend upon the change in an electrical parameter(R, L & C). 2.Example : Piezoelectric transducer & photo voltage cells(for generation of vaoltage in response to illumination) are example of active transducer. 2.Starin gague (for resistance change in response to pressure) & thermistores (from resistance change corresponding tio temperature variations).