Project on embedded system pdf

If we intend to use a small number of parts, we may be better off using chips with PROM. If we intend to use a large number of parts for our application, then the one-time expense of placing our program in ROM is more feasible.

As microcontroller applications become more specialized and complex, needs for maintenance and support rise. Many developers use PROM devices to provide software updates to customers without the cost of sending out new hardware. There are many programmable ROM technologies available which all provide a similar service. A special technique is used to erase the contents of programmable ROM then a special method is used to program new instructions into the ROM.

Often, the developer uses separate hardware to perform each of these steps. Often the shutter is a sticker placed on the window. The eraser bombards the memory with high-intensity UV light. Some devices require an external power source to provide the voltage necessary for erasing and writing and some have an onboard pump which the chip can use to build up a charge of the required voltage.

This makes the configuration available to the modem user after cycling the power on the modem. Often the default or factory configuration settings are stored in ROM and the user can issue a command to restore default settings by overwriting the current contents of EEPROM with the default information.

This saves manufacturers money as they can design and fabricate a single chip and then set the EEPROM blocks to provide special purpose versions with specific capabilities.

Many manufacturers are turning to flash memory. It has the advantages of not requiring special hardware and being inexpensive enough to use in quantity. Manufacturers often provide customers with microcontroller products whose ROM is loaded with a boot or configuration kernel where the application code is written into flash memory.

When the manufacturer wants to provide the customer with added functionality or a maintenance update, the hardware can be reprogrammed on site without installing new physical parts. The hardware is placed into configuration mode which hands control to the kernel written in ROM. This kernel then handles the software steps needed to erase and re-write the contents of the flash memory. Another useful implementation of flash memory includes a device which can connect electronically to a computer owned by the manufacturer.

Such elaborate applications are typically beyond the resources of an 8 bit microcontroller; we mention the example to show the advantage of programmable ROM technologies. Registers are used to control program execution and maintain intermediate values needed to perform required calculations. Some microcontrollers provide access to CPU registers for temporary storage purposes.

This can be extremely dangerous as the CPU can at any time overwrite a register being used for its designated purpose. This means that the C register keyword is meaningless because the compiler can not dedicate a CPU register for data storage. Some C implementations will set aside RAM for special purpose pseudo-registers to use when your application attempts certain operations.

For example, if you attempt a 16 bit math operation, the compiler can dedicate a portion of base page RAM for 16 bit pseudo-registers which store values during math operations.

You can use these special registers for temporary purposes in places where your code will not require them for their intended purpose. You must be careful, if the compiler uses a pseudo-register it will overwrite current contents. The on-chip Flash allows the program memory to be reprogrammed in-system or by a conventional nonvolatile memory programmer. By combining a versatile 8-bit CPU with Flash on a monolithic chip, the Atmel AT89C51 is a powerful microcomputer which provides a highly flexible and cost effective solution to many embedded control applications.

GND Ground. As an output port each pin can sink eight TTL inputs. When 1s are written to port 0 pins, the pins can be used as high impedance inputs. In this mode P0 has internal pull ups. Port 0 also receives the code bytes during Flash programming, and outputs the code bytes during program verification.

External pull ups are required during program verification. When 1s are written to Port 1 pins they are pulled high by the internal pull ups and can be used as inputs. As inputs, Port 1 pins that are externally being pulled low will source current IIL because of the internal pull ups. Port 1 also receives the low-order address bytes low-order address bytes during Flash programming and verification. When 1s are written to Port 2 pins they are pulled high by the internal pull ups and can be used as inputs.

As inputs, Port 2 pins that are externally being pulled low will source current IIL because of the internal pull ups. Port 2 emits the high-order address byte during fetches from external program memory and during accesses to external data memory that use bit addresses MOVX DPTR.

In this application it uses strong internal pull ups when emitting 1s. Port 2 also receives the high-order address bits and some control signals during Flash programming and verification. When 1s are written to Port 3 pins they are pulled high by the internal pull ups and can be used as inputs. As inputs, Port 3 pins that are externally being pulled low will source current IIL because of the pull ups.

RST Reset input. A high on this pin for two machine cycles while the oscillator is running resets the device. Otherwise, the pin is weakly pulled high. Setting the ALE-disable bit has no effect if the microcontroller is in external execution mode. Note, however, that if lock bit 1 is programmed, EA will be internally latched on reset. EA should be strapped to VCC for internal program executions. XTAL1 Input to the inverting oscillator amplifier and input to the internal clock operating circuit.

XTAL2 Output from the inverting oscillator amplifier. To effectively program the it is necessary to have a basic understanding of these memory types. The memory types are illustrated in the following graphic. Program addresses higher than 0FFFh, which exceed the internal ROM capacity will cause the microcontroller to automatically fetch code bytes from external memory.

Code bytes can also be fetched exclusively from an external memory, addresses h to FFFFh, by connecting the external access pin to ground. These bytes can be divided into three different groups as follows: A total of 32 bytes from locations 00 to 1Fh are set aside for register banks and the stack. A total of 80 bytes from locations 30h to 7Fh are used for read and write storage, or what is normally called a scratch pad.

These 80 locations of RAM are widely used for the purpose of storing data and parameters by programmers. This is often in the form of standard static RAM or flash refers to any memory Code, RAM, or other that physically exists on the microcontroller itself. On-chip memory can be of several types, but we'll get into that shortly. As the name suggests, External RAM is any random access memory which is found off-chip.

Since the memory is off-chip it is not as flexible in terms of accessing, and is also slower. For example, to increment an Internal RAM location by 1 requires only 1 instruction and 1 instruction cycle. In this case, external memory is 7 times slower! Code Memory : Code memory is the memory that holds the actual program that is to be run. Flash RAM is also another popular method of storing a program.

Various combinations of these memory types may also be used--that is to say, it is possible to have 4K of code memory on-chip and 64k of code memory off-chip in an EPROM. Registers: In the CPU, registers are used to store information temporarily. That information could be a byte of data to be processed, or an address pointing to the data to be fetched. In the there us only one data type: 8 bits. With an 8- bit data type, any data larger than 8 bits has to be broken into 8-bit chunks before it is processed.

All the above registers are 8-bit registers except DPTR and the program counter. The accumulator A is used for all arithmetic and logic instructions. However, not all the members of the have the entire 64K bytes of on-chip ROM installed. Flag bits and the PSW Register Like any other microprocessor, the have a flag register to indicate arithmetic conditions such as the carry bit. Automatic Zigbee based quick answering systems for multiple users for quiz games and feedback systems.

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Download Free PDF. Shwe Sharma. A short summary of this paper. Ramanpreet kaur 16UEC Mr. The task or work provided to these s y s t e m are very specific and remain s a m e a s once defined by programmer. Micro controllers are us ed in and a s embedded s y s t e m s.

A s for example automatic street light, home automation system, a simple automated electric s tov e etc. Introduction to Electronics Components Resistor Capacitor Multi-meter Pow e r Supply Resistor :- A resistor i s a passive electronic component that w e u se in electronic circuits either to limit current through an active component or to reduce voltage in the circuit by dropping voltage a cro ss the resistor Ratings:- 1.

Mica does not change physically and chemically with a ge Used when small values are required, high stability 50 Pico-farads - 0. Electrolytic:- Large amount of capacitance is required. This makes them poor in applications where precise values are needed. Interrupts: Two External Interrupt source, located at port D. One of them is Serial Peripheral Interface.

Four pins are assigned to Atmega8 to implement this scheme of communication. It has three pins assigned for that. In many projects, this module is extensively used for PC-Micro controller communication. It allows designers to set up a commutation between two devices using just two wires along with a common ground connection, As the TWI output is made by means of open collector outputs, thus external pull up resistors are required to make the circuit.

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