Objective 1 Distinguish between true and false statements concerning the terms in the index for this block, or explain the terms in your own words.
| Boolean processor | a section of the 8051 processor that executes instructions manipulate single bits from 0 to 1 | |
| chips (see also silcon chips) | the basic electronic components of a computer formed on small pieces of silicon | |
| dedicated computer | a computer which is used as a component in mass-produced devices and performs a fixed, predefined task | |
| disassembler | a program for disassembling the contents of the microncontroller's internal program memory | |
| disassembling | a process where a disassembler reads the binary machine code from a programmed microcontroller and converts it back into assembly language | |
| EPROM (electrically programmable read only memory) | program memory that can be programmed electrically after manufacture, and can also be erased and re-programmed. Erasure is achieved by subjecting the memory to ultra-violet light. | |
| EEPROM (electrically erasable programmable read only memory) | a type of memory used for data memory where the data may need to be non-volatile, so normal RAM cannot be used. EEPROM can be erased and reprogrammed electrically by the microcontroller's program | |
| embedded computer | a computer which is used as a component in mass-produced devices and performs a fixed, predefined task | |
| flash memory | program memory that can be programmed electrically after manufacture and the memory can also be erased. Erasure is carried out electrically, and there is no need to erase all the program memory | |
| ICE (in-circuit emulator) | a hardware device used to aid testing and debugging. It replaces the microcontroller in a product under test and is controlled by a general-purpose computer. | |
| integrated circuits |
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| I2C (inter IC) bus | a special synchronous serial interface which provides fast communication to other integrated circuits | |
| latch | a 1-bit device storage unit that temporarily stores data (e.g. in order to prevent the loss of short pulses) | |
| mask-programmable memory | a type of program memory which is programmed with the customer's machine-code program when the device is manufactured and which cannot be erased or reprogrammed | |
| microcontrollers | a device where the processor, main memory and input-output interfaces are all contained in a single integrated circuit (often called a silicon chip) | |
| multiplexed address/data bus | where an 8-bit port is used for both the data and address buses | |
| OTP (one-time programmable memory) | a type of program memory which can be programmed once after manufacture by applying a special set of signals | |
| PCB (printed-circuit board) | an insulating board (commonly made of fibreglass) on which a pattern of copper tracks form the connections between the various components | |
| real-time clock | a time-of-day generator that is separate from the microcontroller | |
| silicon chip | a single integrated circuit | |
| software/hardware trade off | a term used to describe the decisions made when designing an input-output interface, where a particular aspect can be achieved either by using special-purpose hardware or by using software that is larger and more complicated. The hardware solution is usually more expensive but leads to better performance | |
| special-purpose computer | a computer which is used as a component in mass-produced devices and performs a fixed, predefined task | |
| SMD (surface mounted device) | a device where the chip is encapsulated in a smaller package with smaller connecting pins. This method enables the board size to be much reduced. | |
| VFD (vacuum fluorescent display | a type of display which uses electtically heated cathodes, phosphor-coated anodes electrons and voltage to emit light | |
| watchdog timer | a timer used in applications where it is vital that the processor never gets stuck in an endless loop |
Objective 2 Describe what is meant by a microcontroller and draw a block diagram of the main components and interconnections of such a device.
A microcontroller is a device where the processor, main memory and input-output interfaces are all contained in a single integrated circuit (often called a silicon chip). The block diagram is Figure 1, Page 7 of Block 5 of the course text.
Objective 3 Describe the sorts of variations that might typically be expected in a microcontroller family and also the sorts of applications where each variation might be used. (SAQs 3 & 4)
SAQ3 By considering how external memory is attached to the 8051 microcontroller, explain why the number of input-ouput bits would be reduced from 32 to 14 when 64K of external RAM data memory is required.
Using 64K of external RAM data memory means that all the bits in ports 0 and 2 are needed for the external memory's address and data buses. In addition bits 6 and 7 of port 3 are required for the RAM read/write controls. This is a reduction of 2 x 8 = 2 = 18 bits leaving only 14 of the original 32 general-purpose input-output lines.
SAQ4 A remote weather-monitoring device is to be designed that is to be capable of recording large numbers of readings over a long period of time, and is to be made in quantities of up to one hundred. If this device is to contain a microcontroller, outline the characteristics of a family variation that might be suitable for this application.
If the quantity is up to one hundred, then use of a mask-programmed device would not be cost-effective, hence the EPROM or one-time programmable family of variant of the 8051 device would have to be used. If the microcontroller is to be used only for storing many readings, then the program probably would notbe so large as to require external program memory. However, because there is a lot of data to store, external data memory would be needed.
Objective 4 Describe the overall hardware structure of the TMS board. (SAQ 6)
SAQ 6 From the description above (pages 22 - 27). identify those areas of the hardware design which have contributed to minimising cost.
No need for an address decoder
Using a software solution to measure the temperature. However, although the hardware is cheap, the software development cost must also be taken into account. Thus there is a software/hardware trade off.
The components can be mounted on a single-sided printed-circuit board.
Objective 5 Describe the overall operation and structure of the software provided in the TMS board microcontroller (SAQs 7, 8, 9)
Objective 6 Outline the method of temperature measurement chosen for the TMS board. Describe the problems that this method produces, and how these problems are solved.
Objective 7 List and describe both some technical and non-technical aspects that influence the deisgn of a mass-produced device that contains an embedded microcontroller. (SAQs 17, 19)
Objective 8 Explain the idea of a software/hardware trade-off and describe how this idea applies to keyboard scanning and serial communications. (SAQ 12)
Objective 9 For a new, given, microcontroller application, use the information given to draw informed conclusions about its design and about the software/hardware trade-off. (SAQs 13, 16)
Objective 10 Describe the main software development aids available for microcontrollers.
Objective 11 Given a dedicated computer application, draw informed conclusions about the possible structure and requirements of the hardware and software (in terms of processor variant, memory size/type, peripherals/interfacing, processor power/speed, interrupt/polled input-output etc) (SAQs 13, 14, 15, 18)
Other SAQs not mentioned in the objectives list
SAQ 1. From your study of Block 3, Part 4, what features of the 8048 makes it unsuitable for programming in a high-level language such as C?
Machine code produced by a high-level language complier is usually not as compact in terms of program memory requirement as assembly-language programming. In a computer with limited program memory, compactness is very important.
SAQ 2. A company is developing a battery-operated greenhouse temperature monitor that incorporates an embedded controller and is aimed at the mass market. The microcontroller is required to read the greenhouse temperature (which is available as an analogue voltage) at regular intervals and to send the temperature reading to the user's PC via a standard serial connection.
The company estimates the microcontroller's program will require 2010 words of program memory and 40 words of data memory. List the characteristics of a suitable variant of a microcontroller family that might be suitable for this application (a) during development and (b) for production.
The main characteristics of a suitable microcontroller for both development and production are:
A low-power variant to maximise battery life
An analogue-to-digital converter to read the temperature
A standard serial port (UART) to send the temperature to the user's PC
At least 2010 words of program memory. A standard 2K variant would be suitable (2K = 2048 words)
At least 40 words of RAM data memory. A standard 64 word variant would be suitable.
In addition to the above, (a) during development an EPROM or flash memory device would be needed and (b) in production a mask-programmed device would be used.