Pdf 8051 architecture

Even though there are memory locations intended to be occupied by them, the basic core, shared by all types of microcontrollers, has only 21 such registers. Rest of locations are intentionally left unoccupied in order to enable the manufacturers to further develop microcontrollers keeping them compatible with the previous versions.

A Register Accumulator A register is a general-purpose register used for storing intermediate results obtained during operation. Prior to executing an instruction upon any number or operand it is necessary to store it in the accumulator first. All results obtained from arithmetical operations performed by the ALU are stored in the accumulator.

Data to be moved from one register to another must go through the accumulator. In other words, the A register is the most 7 commonly used register and it is impossible to imagine a microcontroller without it.

More than half instructions used by the microcontroller use somehow the accumulator. B Register Multiplication and division can be performed only upon numbers stored in the A and B registers. All other instructions in the program can use this register as a spare accumulator A.

Even though they are not true SFRs, they deserve to be discussed here because of their purpose. They occupy 4 banks within RAM. Similar to the accumulator, they are used for temporary storing variables and intermediate results during operation. Which one of these banks is to be active depends on two bits of the PSW Register. Active bank is a bank the registers of which are currently used. It contains several status bits that reflect the current state of the CPU.

Besides, this register contains Carry bit, Auxiliary Carry, two register bank select bits, Overflow flag, parity bit and user-definable status flag. P - Parity bit. If a number stored in the accumulator is even then this bit will be automatically set 1 , otherwise it will be cleared 0. It is mainly used during data transmit and receive via serial communication. This bit is intended to be used in the future versions of microcontrollers.

OV Overflow occurs when the result of an arithmetical operation is larger than and cannot be stored in one register.

Overflow condition causes the OV bit to be set 1. Otherwise, it will be cleared 0. These two bits are used to select one of four register banks of RAM. F0 - Flag 0. This is a general-purpose bit available for use. CY - Carry Flag is the ninth auxiliary bit used for all arithmetical operations and shift instructions.

For this reason it may be treated as a bit register or as two independent 8bit registers. Explore Audiobooks. Bestsellers Editors' Picks All audiobooks. Explore Magazines. Editors' Picks All magazines. Explore Podcasts All podcasts. Difficulty Beginner Intermediate Advanced. Explore Documents.

Course Overview and Architecture Rv Uploaded by saidarao Document Information click to expand document information Description: Processor. Did you find this document useful? Is this content inappropriate? Report this Document. Description: Processor.

Flag for inappropriate content. Download now. Related titles. Carousel Previous Carousel Next. Jump to Page. Input and output interfaces to handle communications between the microprocessor and the outside world the term port is used for the interface , and.

Memory to hold the program instruction and data. The size of the memory is determined by the number of wires in the address bus. The memory elements in a unit consists essentially of large numbers of storage cells with each cell capable of stroring either a 0 or a 1 bit. The storage cells are grouped in location with each location capable of storing one word.

In order to access the stored word, each location is identified by a unique address. Thus with a 4-bit address bus we can have 16 different addresses with each, perhaps, capable of storing 1 byte, i. It is used to control the demultiplexing of address and data bus. Implied addressing mode: In this, an operand is present in the instruction itself.

Zero address instructions are designed with this addressing mode. The operand is present in this instruction only. The communication systems, where a weak signal is transmitted by the use of a modulation is essential in carrier signal. When the frequency of the high frequency signal is varied in accordance with the intensity of the low-frequency weak signal, the modulation is said to be frequency modulation.

The process of recovering original baseband signal from the modulated signal is called phase modulation. The frequency of the carrier is varied according to the amplitude of the message signal or the intensity of light. Statement 2 is correct. Start Learning. Arithmetic logic unit General purpose registers Control unit Peripherals interfaced. The three basic components of the microprocessor are: ALU Control unit Register unit or register array Control Unit : The entire functioning of the microprocesso r is controlled by the control unit.

The control unit is connected to all the parts of the microprocessor. It allocates resources for the execution of an instruction. It activates necessary circuits in ALU and registers for register array for the execution of an instruction. Arithmetic logic unit : ALU is responsible for carrying out arithmetic and logical instructions in a microprocessor.

It contains different circuits for performing Arithmetic and Logical functions has 8-Bit ALU Accumulator : accumulator is an 8-bit register. Most 8-bit arithmetic and logical operations will take one operand from the accumulator. Answer Detailed Solution Below Option 3 : 0. Calculation: For an 8-bit digital to analog converter, there will be 2 8 combinations. Given that each register has a specific address, it can be accessed directly using that address even if its bank is not the active one.

The bytes have addresses 20H to 2FH. The bits have addresses 00H to 7FH. Specific instructions are used for accessing the bits. In reality, only about 25 of these bytes are actually used. The others are reserved for future versions of the These are registers associated with important functions in the operation of the MCS Some of these registers are bit-addressable as well as byteaddressable. The address of bit 0 of the register will be the same as the address of the register.

Can be referred to in several ways: Implicitly in op-codes. Referred to as ACC or A for instructions that allow specifying a register. Operates in a similar manner to the accumulator. Bit addressable. The B Register Commonly used as a temporary register, much like a 9th R register. Can be accessed as 2 separate 8-bit registers if needed. SP points to the last used location of the stack.

Push operation will first increment SP and then copy data. Pop operation will first copy data and then decrement SP. In , stack grows upwards from low memory to high memory and can be in the internal RAM only. On power-up, SP points to 07H. Register banks 2,3,4 08H to 1FH form the default stack area. Function Auxiliary Carry Flag. Available to the user for general purposes. Register bank select bits.

Set by software to determine which register bank is being used. Overflow Flag Not used Parity Flag. Even Parity. Specify the value to be output on the specific output port or the value read from the specific input port. First bit has the same address as the register. Serial Data Receive Buffer. The other is write-only used for storing serial output data.

Serial Data Transmit Buffer. IE Interrupt Enable. Open navigation menu. Close suggestions Search Search. User Settings. Skip carousel. Carousel Previous.