The 8051 microcontroller has 11 sfr divided in 4 groups. This area of memory cannot be used for data or program storage, but is instead a series of memorymapped ports and registers. The a register is also called the accumulatorand as its name suggests, is used as a general register to accumulate the results of a largenumber of. Special function registers sfr for 8051 microcontrollers.
Introduction to pic16f877 microcontroller architecture and features. Tcon and tmod timer registers of 8051 microcontroller. Special function registers 8051 tutorial tutorials. By muhammad ali mazidi, janice gillispie mazidi, and rolin d. There are 21 special function registers sfr in 8051 micro controller and this includes register a, register b, processor status word psw, pcon etc etc. The sfrs are used as the configuration registers for peripherals within the device as well as control functions for the core. P0,p2,and p3 will perform special function other than io. Know about types of registers in 8051 microcontroller elprocus. Each port has sfr special function registers p0 through p3 which works like a latch, an output driver and an input buffer. Registers are used in the cpu to store information on temporarily basis which could be data to be processed, or an address pointing to the data which is to be fetched.
Most popular in the 1980s and early 1990s, today superseded by enhanced devices with 8051. What is special function register for 8051 microcontroller. This document is, essentially, a compilation of all the tutorial information found on. Special function registerssfrs of 8051 microcontroller brainkart. These two registers th and tl are timer high byte and timer low byte, 0 and 1 are the timers numbers.
When an 8051 microcontroller power up, the stack pointer contained value is 07, by default, as shown in the above figure. Your program may inspect andor change the operating mode of the 8051 by manipulating the values of the 8051s special function registers sfrs. Table 51 8051 special function register sfr addresses the 8051 microcontroller and embedded systems, 2e by muhammad ali mazidi, janice gillispie mazidi, and rolin d. In 8051 microcontroller there certain registers which uses the ram addresses from 80h to ffh and they are meant for certain specific operations. General purpose registers byte addressable registers special function registers bit addressable registers the 8051 microcontroller consists of 256 bytes of ram memory, which is divided into two ways, such as 128 bytes for general purpose and 128 bytes for special function registers sfr memory. With 8bit data type, any data type larger than 8bits. The 8051 microcontroller kenneth j ayala 3rd edition.
Write an 8051 c program to toggle bits of p1 continuously with a 250 ms delay. An sfr can be accessed by its name or by its address. Microcontroller program to generate a square wave of 10 hz at pin p1. Architecture of 8051 microcontroller pdf book manual. Here we use at89c51, in which at mean atmel, c mean cmos technology. Your program may inspect andor change the operating mode of the 8051 by manipulating the values of the 8051 s special function registers sfrs. Each register is 16 bit register divide into lower and. Each register is 16 bit register divide into lower and higher byte register as shown below. The 8051 supports a special feature which allows access to bit variables. Pic 16f84 special function registers pic microcontroller. In the 8051, register a, b, dptr, and psw are a part of the group of registers commonly referred to as sfr special function registers. The 8051 instruction set atmel 8051 microcontrollers hardware manual 4316e80510107 1.
The special function register sfr is the upper area of addressable memory, from address 0x80 to 0xff. Sfrsspecial function registers of 8051 timer registers sfr are registers which contains address of different registers also the main or core functions of microprocessor architecture. Follow this link if you are interested in knowing about differences between a microprocessor and microcontroller. Instead, some special registers in some processor architectures require special instructions to modify them. Every microcontroller has a data memory which is divided into two parts gpr general purpose ram and sfr special function registers. The a and b registers are special function registers which hold the resultsof many arithmetic and logical operations of 8051. In fact, by manipulating the 8051 microcontroller special function registers sfrs, you can assess or change the operating mode of the 8051 microcontroller. The 8051 microcontroller memory is separated in program memory rom and data memory ram. The 8051 architecture 8051 microcontroller hardware, the 8051 oscillator and clock, program counter and data pointer, a and b cpu registers, flags and the program status word psw, internal memory, internal ram, the stack and the stack pointer, special function registers, internal rom, inputoutput pins, ports, and circuits, port 0, port 1. Know about types of registers in 8051 microcontroller. Composed of alu, 16bit program counter and data pointer, 8bit stack pointer, special function or special purpose registers. The memory which is used for general purpose is called as ram memory, and the memory used for sfr contains all the peripheral related registers like accumulator, b register, timers. As shown in the figure below, there are four ports namely p0,p1,p2 and p3, each uses 8 pins, making them 8bit ports. Each special function register is nothing but set of 8 ffs 1 ff1 bit.
The psw is the program status word and controls register banking and. There are 21 unique locations for these 21 special function. T0 and t1 two external and three internal vectored interrupts one full duplex serial io 4. For more information about special function registers, refer to the intel 8bit embedded. The 80518052 microcontroller architecture, assembly language, and hardware interfacing craig steiner universal publishers boca raton, florida. The 8051 family of microcontrollers provides a distinct memory area for accessing special function registers sfrs. Table 51 8051 special function register sfr addresses.
Flag register in 8051 is called as program status word psw. The program memory of the 8051 microcontroller is used for storing the program to be executed i. How to use internal timer registers of 805189c51,89c52. The 8051 microcontroller special function registers are used to program and control different hardware peripherals like timers, serial port, io. Memory locations and registers in the 8051 are, for the most part, eight bits wide. Several of these companies have over fifty versions of the 8051. Special function registers sfrs of 128 bytes 32 io pins arranged as four 8bit ports p0 p3 two 16bit timercounters. Timers and counters in 8051 microcontroller microcontroller and its.
Architecture of 8051 microcontroller the various components of 8051 microcontroller are as follows. The 16f84 special file registers set is organized in two banks, with the most commonly used registers in the default bank 0. If we perform push operation, then the stack pointer address will be increased and shifted to another register. This sfr indicates where the next value to be taken from the. These registers contain all peripherally related registers like p0, p1, p2, p3, timers or. Special function registerssfrs of 8051 microcontroller. Every microcontroller has a data memory which is divided into two parts gpr general purpose ram and sfrspecial function registers. Sfrs are used in your program to control timers, counters, serial ios, port ios, and peripherals. Registers of 80518031 microcontroller timer control register tcon. Special function registers ip, ie, tmod, tcon, scon, and pcon contain control and status bits for the interrupt system, the timercounters, and the serial port. Sfrs reside from address 0x80 to 0xff and can be accessed as bits, bytes, and words. The alu is composed of alu, accumulator, bregister and two temporary.
Serial port control register scon of 80518031 microcontroller the format of scon register is shown. One feature of the 8051 core is the inclusion of a boolean processing engine which allows bitlevel boolean logic operations to be carried out directly and efficiently on select internal registers, ports and select ram locations. There are 21 unique locations for these 21 special function registers and each of these register is of 1 byte size. For example, the p0mdin is a special function register responsible for io pin control. So you may have guessed something from the name itself special function registers known with an acronym sfr. The intel 80196 class microcontroller has 24 sfrs, each 1 byte in size. The registration area or special functions sfr is between 80h and ffh address the internal memory of the microcontroller this memory area can not be used as data memory, it is clear that if we write out of control in the memory allocated to a special register, modify the behavior of the microcontroller, resulting in. The 8051 microcontroller special function registers are used to program and control different hardware peripherals like timers, serial port, io ports etc. Special function registers are upper ram in the 8051 microcontrollers. The 8051 is a flexible microcontroller with a relatively large number of modes of operations. Microcontroller 8051 is basic among all the mcus and excellence for beginners.
Almost all microcontrollers, including 8051 microcontroller implement harvard architecture. Each consists of a latch an output driver, and an input buffer. In 8051, there is one data type is of 8bits, from the msb most significant bit d7 to the lsb least significant bit d0. The tcon register consists of timer overflow flags, timer run control bits, external interrupt flags and external interrupt type control bits. We can access the registers directly or by their addresses. The 8051 microcontroller consists of 256 bytes of ram memory, which is divided into two ways, such as 128 bytes for general purpose and 128 bytes for special function registers sfr memory. Registers in 8051 math register indicates that each bit a of the register can be programmed. These registers are called special function registers sfrs.
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