Configuration Pin Microcontroller AT89S51AT89S51 microcontroller pin arrangement shown in Figure 1.

Figure 1. Pin Configuration AT89s515. Functionality of Each Pin Microcontroller AT89S51Microcontroller AT89S51 has pins numbered 40 and generally packaged in DIP (Dual Inline Package). Each pin on the microcontroller AT89S51 have utility as follows:Port 0Port 0 is a function of two ports are on pins 32-39 of AT89S51. In the design of a simple system of this port as the port I / O versatile. For more complex designs involving this pathway dimultiplek external memory to the data bus and address bus.Port 1Port 1 is reserved as I / O ports and are on pins 1-8. Some pins on this port have special functions ie P1.5 (MOSI), P1.6 (MISO), P1.7 (SCK) is used to track the download program.Port 2Port 2 (pins 21-28) is a dual function as a port I / O versatile, or as high-byte address bus for design involving external memory.Port 3Port 3 is a two-port pin functions are at 10-17, this port has multiple functions, such as those found in table 1.1 below:ALTERNATE ADDRESS BIT BIT NAME FUNCTIONB0h P3.0 RXD Receive Data for serial portB1h P3.1 TXD Transmit Data for serial portB2h P3.2 INT0 External interrupt 0B3H P3.3 INT1 External interrupt 1B4h P3.4 T0 Timer / counter 0 external inputB5h P3.5 T1 Timer / counter 1 external inputP3.6 WR B6h External Data memory write strobeP3.7 RD B7h External Data memory read strobePSEN (Program Store Enable)Is an output signal that is contained in the pin 29. Its function is as a control signal to allow a microcontroller to read the program (code) of the external memory. Normally this pin is connected to pin EPROM. If the execution of the program from the internal ROM or flash memory (ATMEL AT89Sxx), then it is in the off state (high).ALE (Address Latch Enable)ALE output signal which is at pin 30, the same function with ALE in microprocessor INTEL 8085, 8088 or 8086. ALE signal is used to demultiplek address bus and a data bus. ALE signal generate pulses at 1/6 the oscillator frequency and can be used as a clock that can be used in general.EA (External Access)Input signals are on pins 31 which can be given a logic low (ground) or logic high (+ 5V). If given the high logic microcontroller will access the program from the internal ROM (EPROM / flash memory). If given a logic low, the microcontroller will access the program from an external memory.RST (Reset)Reset input on pin 9 is the master reset for AT89S51. Pulse transition from high to low during the second cycle will reset the microcontroller.OscillatorProvided on chip oscillator driven by XTAL connected to pin 18 and pin 19. Necessary stabilizing capacitor of 30 pF. Great value XTAL about 3 MHz to 33 MHz. XTAL1 is the input to a reversal of the oscillator amplifier (inverting oscillator amplifier) ​​and input to the internal clock operating circuit. While XTAL2 is the output of the oscillator amplifier reversal.PowerAT89s51 operated at a supply voltage of + 5V, Vcc pin is at number 40 and the Vss (ground) at pin 20.

Microcontroller AT89S51

Microcontroller type AT89S51 an MCS-51 microcontroller family with the exact same configuration with AT89C51 is quite well known, only AT89S51 features the ISP (In-System Programmable Flash Memory). This feature allows the microcontroller can be programmed directly into an electronic system without going through the Programmer Board or Board Downloader. The microcontroller can be programmed directly via ISP cable that is connected to the parallel port on a Personal Computer. As for the features of the microcontroller AT89S51 is as follows:

1. A CPU (Central Processing Unit) 8 bits including MCS51 family.2. The internal oscillator and timer circuit, 128 bytes of internal RAM (on-chip).3. Four Programmable I / O ports, each consisting of eight channels of I / O4. Two Timer Counter 16 bits.5. Five interrupt lines (2 external interrupt and internal interrupt 3)6. A serial port with full duplex UART serial control.7. The ability to carry out the operation of multiplication, division and Boolean operations (bit)8. Speed ​​instruction execution per cycle 1 microdetik at a clock frequency of 12 MHz9. 4 Kbytes of Flash ROM which can be filled and removed up to 1000 times10. In-System Programmable Flash MemoryWith the above feature, making the tool use AT89S51 to be more simple and does not require a lot of IC supporters. So the AT89S51 microcontroller has a privilege in terms of hardware.

Usefulness Microcontroller

Microcontroller has become common for use in a variety of areas, and can be found in household appliances, computer peripheral equipment and instrumentation. Microcontroller is also widely used in cars, many industries that use them, and have become a central part of the robotics industry. Because it is used to control a single process and execute the instructions are simple, mikorkontroler not require a large processing power.
The automotive market has been a key driver of the development of microcontrollers, many of which have been developed for automotive applications. Because microcontrollers used in automotive must face the harsh environmental conditions, they must be highly reliable and resilient. However, automotive microcontrollers, as well as other microcontrollers, is a product which is very cheap and can provide advanced features, without the encouragement of the development of the industry may be things that are not possible or would be very costly to implement.

Microcontroller

A microcontroller is an integrated chip that typically becomes part of an embedded system (a system designed to perform one or more specific functions in real time). Microcontroller consists of CPU, Memory, I / O ports and timers like a standard computer, but because it is designed only to carry out a specific function in regulating a system, this microcontroller shape is very small and simple and includes all the necessary functions on a single chip ,Different microcontroller with mikroprocesor, which is a general-purpose chip that is used to make a computer or a multi-function devices that require several chips to handle multiple tasks. Microcontroller is intended to be self-sufficient and independent, and serves as a small dedicated computer.The great advantage of the microcontroller compared to using larger microprocessors, is that the number of components and the cost of the design of controlled items can be kept at a minimum. Microcontroller typically designed using CMOS technology (complemantary Metal Oxide Semiconductor), an integrated chip manufacturing technology (IC) efficiently uses little power and is more immune to electrical surges compared to other techniques.