btec nc - microprocessor systems and application - application and principles of operation of...

Brendan Burr BTEC National Certificate in ElectronicsApplications and Principles of Operation of

Microprocessor Based Systems

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Task 11.1 a) A microprocessor system required for a self employed designer

draughtsman working from home.

Hardware needed/selectedThe designer draughtsman would need a number of peripheral devices to aid in the activities he/she would undertake.This could include a trackball which would aid in the prevention of repetitive strain injuries on the wrist.The basic peripheral devices would also be required, to be able to work the Operating System and to open the drawing software, such as Mouse, Keyboard and Monitor.The mouse or trackball wouldn’t be a standard type, as they would be specific for designing on a CAD package.An output device such as a printer or plotter, to be able to withdraw the information and give it to the customer, as well as a large monitor for the design work to be undertaken easily and effectively.The processor would be working at a high rate, so a cooling fan would be required.

The Operating SystemThe type of OS I would suggest would be a Multi-Tasking Operating System, as the designer draughtsman may want multiple applications available to him/her whilst having the drawing software open.This would cost a greater amount than a simpler Operating System, but it spares the designer draughtsman the hassle of having to have multiple machines.

The CPU specificationThe CPU would have to be quick, to take full advantage of the amount of memory available.The graphics from a potential CAD package would require a lot of computing power, so may require an individual microprocessing unit to handle this. Multiple Processors would be required if graphics, networking and visual processing was incorporated into the Microprocessing Unit.

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Memory requirementsImages can take up a lot of memory and can slow the microprocessing unit a considerable amount. For this reason I think it would be appropriate to have plenty of memory available. This would be Random Access Memory (RAM), so the Microprocessing unit is able to carry out the Fetch Execute Cycle, and can then complete the programmed routines much smoother than if there was a lesser amount of memory available.The designer draughtsman can then also have multiple applications open at the same time, and still have a smooth operation of the microprocessing unit.

Software installedThere would be a drawing software package, suitable to the designer draughtsman’s need.Which would include a means of extracting the information, so printing/plotting software should be available.For ease of communication between the designer draughtsman and his/her customer, a suitable Electronic Mail package would be suitable for quick and cost effective means of communication.

Communication ports usedThe drawing files could be large, so Firewire cables could be used to communicate large pieces of information between the hard drive and the Motherboard, however the cost of this is greater than the more established IDE cables, which I feel would do just as good a job.The old P/S2 cables are becoming more and more obsolete, so I would recommend the modern day standard of USB 2.0 for the Keyboard and Mouse.The computer would be linked to a phone line/modem to connect it to the internet, so a suitable RJ45 cable could be used for data communications to the customer.

IEEE protocols/specificationThe potential for the microprocessor to be connected to the internet, means that there will be IEEE protocols that have to be followed.The types of cables available for the interior of the computer are minimal, but I would suggest a FireWire 400 (IEEE1394-1995). This is because the data transfer rate is over and above the potential speed required by the processor.As for an outside source, to the router, I would suggest that an Ethernet cable is suitable with RJ45 connecting plugs.

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b) A microprocessor system for a news paper editor working in a commercial environment.

Hardware needed/selectedAs with the designer draughtsman, the newspaper editor is likely to need a number of peripheral devices to be able to carry out his/her operations.A visual display unit would be required to allow the user to monitor his/her progress in the editing of the newspaper, it may be a good idea for the monitor to be a larger screen, or possibly two screens side by side with software installed to allow them to work consecutively.Newspapers tend to be mainly text, so a keyboard and mouse would also be required for the editor to be able to locate and actually edit the onscreen information.The processing unit may become hot, as editing tends to take a long time it is likely that the unit will be powered for a long period of time. This means that the unit may require a cooling device, such as a fan.A media source would be required, to ensure that the peripheral devices software could be installed from an outside source.USB 2.0 ports may be required for access to Flash Memory drives, in case the newspaper editor needs to remove some information and take it to a different media source.A Video Graphics Card would be suitable as the images would require a fairly decent interpretation sent to the monitor(s). High Definition may be a good idea but this would be expensive and increased cooling would be required to prevent overheating.

The Operating SystemThe operating system I would suggest would be a multi task operating system, as this would suit the editor and his/her extended tasks.This will allow networking to multiple computers, so editing can be done on the same document (newspaper) by many different people at the same time, increasing the speed and accuracy of production tremendously.

The CPU specificationThe CPU on this microprocessing unit would have to be fast and able to run multiple applications at the same time, without causing a delay in the operations.The editing software would be complex, so it must be able to run it as smoothly as possible, to ensure that the editor is not type and only half of the letters are appearing on screen due to the other letters not being processed.

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Memory requirementsPlenty of memory would be required for the CPU to access. This would be in the form of RAM so there would always be a place for the CPU to store information before it is executed.The main storage device would also have to be significant as the files for a newspaper editing (if it included many images) could be quite big. However if there was a small network, to improve the production rate of the editing, then a server may be used and a much bigger hard drive would be available on the network.There would also have to be the standard forms of memory, such as the registry files, ROM, RAM and a cache.

Software installedA word/image editing software would be the main requirement for the editors’ microprocessing unit.There may also be a necessity for an electronic dictionary, which will allow the editing to be precise and quick, as they wouldn’t need to trawl through a dictionary to check for spellings.All of the usual stored information for the peripheral devices would be required, so these would have to be downloaded and installed onto the hard drive.

Communication ports usedIf the computer was connected to other computers to enable a faster editing process , then it is likely for RJ45 ports to be required. It is a similar basis to that of the designer draughtsman, where the documents which are worked on by the newspaper editor have the potential to be large, if this is the case then storing the document may take some time as the microprocessing unit would have to write to the hard drive. If normal IDE cables were used then the writing could take a long time, however a speed upgrade would be available if the motherboard had Firewire ports. If these were utilised then the cost of the unit would also increase as the technology has only been around for a few years, but the old technology has a few more years before becoming obsolete.USB 2.0 ports would be required as the work may be required for extraction from the system, to a different microprocessing unit. The system may also require updates this would be another available access point.

IEEE protocols/specificationThe networking potential for the newspaper editor means that there is also a requirement for the Ethernet cables with RJ45 plugs. I wouldn’t suggest that FireWire cables (IEEE1394-1995) were used as the length of the cable is limited to around 70 metres and the cost of this would be higher than the Ethernet cables, without a great deal of benefit.

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c) A microprocessor system for a production manager working in an industrial environment.

Hardware needed/selectedThe type of microprocessing system required for a production manager would be similar to those of the previous two systems. The basic hardware such as a keyboard, mouse and monitor would be required. The processing required for a manager may be substantial as they would be the person who tracks and monitors the progress of the work that the production team would carry out. So a cooling fan would be required, as well as a well ventilated tower for the motherboard, CPU and other hardware components.The hard drive would be the main source of storage of the information regarding the work undertaken. It may be suitable for the production manager to have access to the work that his/her team have been working on. A networking capability should be available in case the production manager requires the system to be upgraded to fulfil these criteria.

The Operating SystemAs with the previous two operating systems I would suggest a multi task operating system. In the long run this type of system would potentially save money as there are likely to be multiple tasks the user is going to undertake, and having multiple machines is just not feasible.Windows Vista would be a suitable software package, however this is the most recent version and requires a 64bit processor which is one of the fastest on the market.If the operating system was downgraded to Windows XP then a lot of the applications would still be available, however the system would operate well on a 32bit processor.

The CPU specificationAs discussed above in the operating system. Depending on which type of operating system is purchased would depend on the CPU requirement. If it was thought that Windows Vista is the best option then a 64bit 1GHz processor is necessary, however if Windows XP is used then the processor can be downgraded to 32bit.Other software requirements wouldn’t require more than a 16bit processor as they would be generally standard packages.

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Memory requirementsDepending on the types of software and operating system the production manager will be using will also vary the memory requirements with regards to RAM. 1GB of RAM would be the minimum requirement for the basic Windows Vista Operating System, a lesser demanding operating system such as Windows XP could get away with 512MB of RAM.The hard drive required would have to be sufficient enough for the production manager to store basic files as well as potentially large files also, so I would say around an 80GB hard drive would last a long time.

Software installedThe software required for the production manager would be mainly for organisational purposes. Microsoft Outlook would provide a communications area as well as a place to monitor times and schedules for meetings.If the manager has a Personal Assistant then it may not be necessary for his/her microprocessing unit, however it would still be recommended that it was installed so that they are also able to keep track of their arrangements.Software which will enable the manager to open files that the other workers have been working on would also be required, to help monitor the progress made on each task. Internet access may be required to enable the manager to carry out researching tasks for development of the business may also be necessary.

Communication ports usedAn Ethernet cable would be necessary if the production engineer requires the use of the internet and networking. This being the case an RJ45 connection port must be available for the connection of this type of cable.The mouse and keyboard can be connected using a standard USB 2.0 connection port, just like in the previous two examples of microprocessing units. The monitor would require a VGA port, this would give standard graphics to the monitor, and not High Definition, which I think would be suitable as the production manager would only be using standard software.

IEEE protocols/specificationThe protocols for the production managers microprocessing system would be much the same as the previous two examples. So for potential internet access an Ethernet cable could be used, which is what I would suggest as in an industrial environment the computers can be great distances, so this would be the most cost effective way of connecting all the computers to one terminal and allow internet access.

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Task 22.1 Describe the architecture and principles of the operation of a

microprocessor based system.

The Microprocessor based system is a relatively simple concept, however the actual workings of the system are complex.Once the system is powered on the Central Processing Unit gathers the required information for initialisation. This is stored in the Read Only Memory, which holds information which cannot be changed. In a common Personal Computer the BIOS is loaded. This resets everything in the processor to the correct state to allow the source code to be processed.For quick access the registers hold the initialisation code, to ensure that everything is in a neutral state before the processes are carried out.Once this is done, the main code can be processed. This will be stored in the Hard Drive (RAM), where the program will remain until it is called. It could be called by an outside user, for example double clicking a mouse on an application icon would result in data being sent down the Bi Directional Data bus to the microprocessing unit. The microprocessing unit will then process the requirement for the application to be opened and will fetch it from the Hard Drive.The application data will have a unique address which will allow the microprocessing unit to accurately find the correct data and read it in the correct sequence, this will located via the address bus.The application data will then be sent to the microprocessing unit for it to be processed. This will be completed with the aid of information stored in the ROM.Once the application data has been loaded, it will gradually display this information on output devices, such as the VDU (Visual Display Unit) and allow further input from the user such as text input from a keyboard.

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The Fetch Execute Cycle

This is when the CPU collects information from the memory and executes it.Each piece of stored information is given an individual and unique identification, this allows the CPU to correctly process the operation in the correct sequence.This process enables the system to work twice as fast, as it is able to “fetch” a code whilst at the same time “execute” the earlier code also. By doing this the system is always working to a much faster rate than if it were to individually fetch and then execute and then fetch the next piece of code.

2.2 Functions of a microprocessor

a) CPUThis is the abbreviated term of the Central Processing Unit. It carries out the bulk of the data processing. It is basically the brain in the computer which does most of the work, with regards to executing the program source code which is stored in the memory until the CPU calls it and it is fetched for processing.Modern CPU’s like those in Personal Computers are in a square packaging and have multiple pins on the underside which connect to the motherboard.

b) ALUThis is the acronym of Arithmetic Logic Unit. It calculates the arithmetic operations, such as addition, subtraction, division and multiplication.In even the most basic of Microprocessors there is usually a number of ALU’s, allowing for multiple calculations to be worked to maintain its use in circuits such as timers.The binary subtraction method of two’s compliment would be done using the ALU, resulting in no need for complex calculation units in the system.

c) RegistersThis is a small amount of memory within the microprocessing unit, which can be accessed much more quickly than if the information were stored in memory elsewhere on the system.It would contain information such as initialisation code, so upon starting up the microprocessor could reset to the correct state an begin the operations much more quickly.

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d) RAMThis is the acronym of Random Access Memory. It is known as “random” as the information can be accessed in any order.The most modern type of RAM is the DDR2 range which can have up to 16GB or memory.This is the place where pieces of information are dumped until the CPU is ready to execute them.

e) ROMThis is the acronym for Read Only Memory. It has code written to it which cannot be modified (in basic ROM). The words “read only” mean that the CPU only reads the information on there (such as a start up sequence) and does not write anything to it, which may potentially alter the start up sequence for the next time.There is a variety of types of ROM, such as EPROM (Erasable Programmable Read Only Memory) and EEPROM (Electrically Erasable Programmable Read Only Memory) which all enable the user to reprogram the ROM chip to alter the code. This would have to be done on computer software and loaded onto the chip.

f) I/OThis is the acronym for Input and Output Devices. These are the devices which allow things outside the system to have an input into an operation.The most basic input devices would be items such as keyboards and mice, along with joysticks and control pads for gaming, pallets and trackballs for designing.Input devices could also include infra red sensors which, once active, can give a hi/lo state and result in the software triggering a motor (Output Device) and opening a door. There are also a number of output devices, such as VDU’s (Visual Display Units) which allow the user to monitor what a system is actually doing, along with printers which can print off another type of visual representation.Speakers could also be an output device to enable people to listen to digital music from a computer.

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Task 33.1 Compare the architecture and principles of operation of the two

following types of microcontrollers / microprocessors.

My chosen chips are the PIC16F84A and the PIC16F627A.I chose these chips as they have a similar architecture so the comparison should be much clearer between the two.

First of all I will compare the CPU Features.

PIC16F84A

PIC16F627A

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For both of the High Performance RISC CPU’s there are only 35 single-word instructions which are single cycle, except for the program branches which are two cycle. This offers a programmer friendly chip, as the code will not be extremely complex to write and the programmer would be able to pick up and remember all of the code words within a short space of time.

Both of the chips have identical operating speeds of DC - 20 MHz for the clock input, however the PIC16F84A also has a DC – 200ns Instruction Cycle.

Both of the chips also have Direct, Indirect and Relative Addressing modes along with an 8 level deep hardware stack.

The PIC16F84A would appear to have a lot more features than the PIC16F627A. From the two extracts of the individual PIC’s from their Datasheets I would expect to be buying a better performing chip if I were to purchase the PIC16F84A, this is because it has more features with regards to the CPU.The additional features are:

1024 words of program memory68 bytes of Data RAM64 bytes of Data EEPROM14-bit wide instruction words8-bit wide data bytes15 Special Function Hardware registersDirect, indirect and relative addressing modesFour interrupt sources:- External RB0/INT pin- TMR0 timer overflow- PORTB<7:4> interrupt-on-change- Data EEPROM write complete

These are all features that the PIC16F627A doesn’t have according to the datasheets. These limitations could result in a much better performing Microcontroller at a cost not much greater than that of the lesser Microcontroller.

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Next I will compare the Special Microcontroller Features, for both the PIC16F84A and the PIC16F627A.PIC16F84A

PIC16F627A

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The PI16F84A has 10,000,000 typical erase/write cycles available of Electronically Erasable Programmable Read Only Memory. Comparing this to the 1,000,000 EEPROM endurance of the PIC16F267A chip, you can clearly see that the PIC16F84A has an endurance 10 times that of the PIC16F267A chip.However, the PIC16F267A’s FLASH memory endurance exceeds the PIC16F84A. This is clearly seen by the PIC16F84A 100,000 and the PIC16F84A having a mere 10,000.

Both of the chips have a 40 year data retention lifespan, which is a significant length of time.

For the special features, I would say that the PIC16F84A is a much better chip, but not by a large amount. This is because in terms of erase/write cycles both of the chips are similarly matched, with them both being ten times greater than one another in either field.

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I will now compare the Peripheral Features.PIC16F84A

PIC16F627A

The PIC16F84A has 13 Input / Output pins which have individual direction control. The PIC16F267A has 16 giving this chip a slightly better advantage.Both chips have high current sink/source for direct LED drive capability. Also both chips have Timer0: 8-bit timer/counter with 8-bit programmable prescaler.

The PIC16F267A is a better chip in this category also.

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Next I will compare the pin configuration.

PIC16F84A

PIC16F627A

Here is the layout of the pin configuration of both types of the PIC16F84A and the PIC16F627A. As you can see, for both of the microcontroller chips the packaging remains fairly similar, with the amount of pins available remaining exactly the same for the PDIP, SOIC and the SSOP chips for both the PIC16F84A and the PIC16F627A.The PIC16F627A is clearly the updated version of the series as it has more functions available for each of the pins, as shown above.

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Finally I will compare the Block Diagrams of the workings of the two chips.

PIC16F84A Block Diagram

The PIC16F84A Block Diagram shows that there are two Uni-Directional data bus’ going to the Electronically Erasable Programmable Read Only Memory Data Memory block on the diagram. This would suggest to me that one is for entry of the programmable data, which will be stored in the EEPROM Data Memory Block, the other will allow this data to be erased or will allow the EEPROM Data Memory to be reset.There are numerous input and output blocks on this diagram. Out of the 20 pins available on the IC, there are only 7 pins labelled on this Block Diagram.

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PIC16F627A Block Diagram

There is a significant similarity to the two block diagrams of the PIC16F84A and the PIC16F627A Chips.The bulk of this block diagram is the same, however there are also major differences.The EEPROM Data Memory Block has completely moved to the base of the diagram and is now linked to the other new sections of the chip (as discussed above) such as the Comparator, VREF, Timer0, Timer1, Timer2, CCP1 and the USART.There are also two new entrances into the Block in the centre of the diagram that previously housed only the Power-Up Timer, Oscillator Start-Up Timer, Power-On Reset and the Watchdog Timer. It now contains these Timers as well as the Brown-Out Reset and the Low-Voltage Programming.PORT A and PORT B are now symbols that indicate the majority of the pins as inputs and outputs. Out of the available 20 pins on the chip 19 are indicated on the Block Diagram, giving a much more informative approach than the PIC16F84A Block Diagram.

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btec nc - microprocessor systems and application - application and principles of operation of...

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memory available

drawing software package

principles of operation

microprocessor system

drawing software open

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designer draughtsmans

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