Microcontroller A microcontroller (mcu or µc) is a small computer on a single integrated circuit consisting of a relatively simple CPU combined with support functions such as a crystal oscillator, timer, watchdog, IO etc. Microcontrollers are designated for small applications. Thus, in contrast to the microprocessors used in personal computers and other high performance applications, simplicity is emphasized. Microcontrollers operate at frequency as low as 12 MHz, as this is adequate for many typical applications, enabling low power consumption (mill watt or nanowatt).
Microcontroller is used in automatically controlled products and devices, such as automatic control system, appliances and toys. | Microprocessors | Microcontroller | |1. It is just a CPU. |1. Include CPU+ I/O+ RAM+ROM+TIMERS+SERIAL COMM | | |On a single chip. | |2. Operates at high frequency ie, 2. 06GHz. |2.
Operates at a low frequency ie,12 MHz | |3. It is general purpose, i. e. more than on operation can be perform |3. It is single purpose ,i. e. can perform only one task at a time. | |simultaneously. | | |4. Costly |4. Cheap. | Introduction to 8051 microcontroller Input /Output pins 32 RAM 128 bytes ROM 4K bytes Timers 2
Interrupt sources 6 Serial port 1 Pin Diagram and Description [pic] Pin 1-8(PORT 1): Each of this pin can be configured as an input or output. Pin 10-17(PORT 3): Each of these pins can serve as general input or output. Besides, all of them have alternate function: Pin 10(RXD): Receive data serially. Pin 11(TXD): Transmit data serially. Pin 12(INT0): Interrupt 0 input. Pin 13(INT1): Interrupt 1 input. Pin 14(TO): Timer 0 input. Pin 15(T1): Timer 1 input. Pin 16(WR): Write to external memory.
Pin 17(RD): Read from external memory. Pin 18,19(X2,X1): A quartz crystal which specify operating frequency is connected to these pins. Pin 20(GND): Ground. Pin 21-28(PORT 2): If there is no intention to use external memory then these pin are configured as general inputs or outputs. In case external memory is use the higher address byte, i. e. address A8-A15 appears on this port. Pin 29(PSEN): PSEN stand for program store enable if external ROM is used then this pin is connected to OE pin of ROM.
Logic 0 appears on it every time µc read a byte from memory. Pin 30(ALE): Address latch enable is an output pin and is active high. It multiplexes address and data from port0, i. e. ALE indicates if P0 has address or data when ALE=0 it provides data, but when ALE=1 it has address. Pin 31(EA): EA stand for external access, If program is present in internal memory then this pin is connected to Vcc=5v, but if the code is present in external memory then it is connected to ground.
Pin 32-39(PORT 0): If external memory is not used then these pins can be used as general input/output. Otherwise, P0 is configured as address output (A0-A7) when ALE=1 and data output when ALE=0. Other port pins consist of built in pull up resistors but pins of this port have this resistors left out so external pull-up resistors of 10k are connected to port 0. Pull up means pulling the voltage to +5V so as to get the effective output. Pin 40(Vcc): +5V power supply.