05-06-2012, 03:25 PM
Microcontroller Based Electronic Message Board
Electronic Message Board.doc (Size: 780.5 KB / Downloads: 4)
Abstract
The LED electronic message board is one of the fastest media to make people up to date. Message can be send through serially via keyboard or send by IR transmitter. It can perform multiple tasks like it displayed flash news up to 700 characters. It has also the ability to show time and date and at the same time it senses the temperature after every second and displays it on LED patches. It has many advantages like image cannot become fuzzy through long distances. Power consumption of LED electronic message board is very low as compared to LCD board. It has many wide applications. It can be installed easily anywhere like in airports, hospitals, universities, banks and etc.
8051 Microcontroller and Its Architecture
The Intel 8051 is a single chip microcontroller (µC) which was developed by Intel in 1980 for use in embedded systems. Intel's original versions were popular in the 1980s and early 1990s.
8051 based microcontrollers typically include two or three timers, 128 or 256 bytes of internal data RAM (16 bytes of which are bit-addressable), up to 128 bytes of I/O, 512 bytes to 64 kB of internal program memory, and sometimes a quantity of extended data RAM (ERAM) located in the external data space. The original 8051 core ran at 12 clock cycles per machine cycle, with most instructions executing in one or two machine cycles. With a 12 MHz clock frequency, the 8051 could thus execute 1 million one-cycle instructions per second or 500,000 two-cycle instructions per second. Enhanced 8051 cores are now commonly used which run at six, four, two, or even one clock per machine cycle, and have clock frequencies of up to 100 MHz, and are thus capable of an even greater number of instructions per second.
Important features:
The 8051's predecessor, the 8048, was used in the keyboard of the first IBM PC, where it converted key presses into the serial data stream which is sent to the main unit of the computer. The 8048 and derivatives are still used today [update] for basic model keyboards.
The 8031 was a cut down version of the original Intel 8051 that did not contain any internal program memory (ROM). To use this chip external ROM had to be added containing the program that the 8031 would fetch and execute.
The 8052 was an enhanced version of the original 8051 that featured 256 bytes of internal RAM instead of 128 bytes, 8 kB of ROM instead of 4 kB, and a third 16-bit timer. The 8032 had these same features except for the internal ROM program memory. The 8052 and 8032 are largely considered to be obsolete because these features and more are included in nearly all modern 8051 based microcontrollers.
Pin Configuration of Microcontroller 8051:
The microcontroller has total forty pins in all. Most of the pins of 8051 microcontroller have more than one function. The first function is the input /output operation and the second function can be some special function like they can be used as counters or for serial communication.
In microcontroller there are four ports (collection of pins) P0, P1, P2 &P3. These ports have 8 pins each as shown. As we will see later on we will be able to address the whole port during programming.
Whenever we are talking about 8051 we are talking of the family of microcontrollers having the architecture of 8051. They are all same except for some additional features, pins distribution and packaging.
Special Function Registers:
Special Function Registers (SFRs) are given in the figure given below. Each of these registers as well as each bit they include, has its name, address in the scope of RAM and precisely defined purpose such as timer control, interrupt control, serial communication control etc. Even though there are 128 memory locations intended to be occupied by them, the basic core, shared by all types of 8051 microcontrollers, has only 21 such registers. Rest of locations is intentionally left unoccupied in order to enable the manufacturers to further develop microcontrollers keeping them compatible with the previous versions. It also enables programs written a long time ago for microcontrollers which are out of production now to be used today.
