8051 Microcontroller

The 8051 is an 8 – bit Microcontroller i.e. it can read, write and process 8 – bit Data. CPU is the brain of any processing device of the microcontroller. It monitors and controls all operations that are performed on the Microcontroller units. 

ALU or Arithmetic Logic Unit, as the name suggests, performs 8 bit Arithmetical and Logical Operations over the operands held by the temporary registers TMP1 & TMP2.

The 8051 contains 34 general purpose or working registers. Two of these Register A (Accumulator ) and B.

Accumulator (ACC): The immediate result is stored in the accumulator register for next operation.

 B register: It is a register just for multiplication and division operation which requires more register spaces for the product of multiplication and the quotient and the remainder for the division.

Program status word (PSW): This register   contains information about the status of the program. The PSW register has several bits that reflects the current status of the CPU.

Program counter (PC): The program counter points to the address of the next instruction to be Executed. The program counter is 16 bits wide.

Data pointer (DPTR): The data pointer is 16 bit register. It is used to hold the address of the data in the memory.

Stack pointer (SP): The stack is a section of RAM used by the CPU to store information temporarily. This information could be data or an address. The register used to access the stack is called the SP register. The stack pointer in the 8051 is only 8 bit wide.

Memory: Microcontroller requires a program which is a collection of instructions. This program tells microcontroller to do specific tasks. These programs require a memory, which is used to store the program of the microcontroller is known as Program memory. It is known as ROM memory to store data or operands temporarily of the micro controller. The data memory of the 8051 is used to store data temporarily for operation is known RAM memory.

Interrupts: Interrupts is a sub-routine call that given by the microcontroller when some other program with high priority is request for acquiring the system buses the n interrupts occur in current running program.

Oscillator: As the microcontroller is digital circuit therefore it needs timer for their operation. To perform timer operation inside microcontroller it required externally connected or on-chip oscillator is used inside microcontroller.

BUS : Basically Bus is a collection of wires which work as a communication channel or medium for transfer of Data. Here two types of buses that are shown in below

• Address Bus: 8051 microcontrollers is consisting of 16 bit address bus. It is generally be used for transferring the data from Central Processing Unit to Memory.
• Data bus: 8051 microcontroller is consisting of 8 bits data bus. It is generally be used for transferring the data from one peripherals position to other peripherals.

Timing & Control unit: This unit derives all the necessary timing and control signal required for the internal operation of the circuit. It also derives control signals required for controlling the external system bus.

Port 0 to Port 3 Latches & Drivers: These four latches and driver pairs are allotted to each of the four on chip I/O ports. These are identified as P0, P1, P2, P3.