Lower 4bits are used for control operation of timer. A device which contains the microprocessor with integrated peripherals like memory, serial ports, parallel ports, timercounter, interrupt controller, data acquisition interfaces like adc, dac is called. Timers of 89c51 microcontroller microcontroller projects. Interrupts are the events that temporarily suspend the main program, pass the control to the external sources and execute their task.
The register a is located at the address e0h in the sfr memory space. Aug 08, 2019 now if we again want to run the timer make trx1. The at89s52 is a lowpower, highperformance cmos 8bit microcontroller with 8k bytes of insystem programmable flash memory. Pcon powersave control register tcon,tmod timer control registers tl0,th0 16bit timer register auxr aux.
Scribd is the worlds largest social reading and publishing site. An interrupt is a signal to the processor emitted by hardware or software indicating an event that needs immediate attention. Register bank select bits in the program status word psw. This register contain not only the mode selection bits but also the 9th data bit for transmit and receive tb8 and rb8 and the serial part interrupt bits ti and ri scon serial port control register smo serial port mode 0 shift register. In this tmod register, lower 4 bits are set aside for timer0 and the upper 4 bits are set. This bit in tmod register is used to know whether it is used as a delay generator or as an event counter. Timer registers tcon timer control register tcon is an 8bit register. Copy the byte in tcon to register r2 using at least 4 different methods. The serial port of 8051 microcontroller supports full duplex communication i. Digital potentiometers design guide microchip technology. The tcon register has a 1bit flag, tf for each timer to indicate the timer overflow or end of timing. Microprocessor microcontroller arithmetic and logic block diagram of microprocessor block diagram of microcontroller microprocessor contains alu, general purpose registers, stack pointer, program counter, clock timing circuit, interrupt circuit microcontroller contains the circuitry of microprocessor, and in addition it has built in. Port 2 also receives the highorder address bits and some control signals during flash programming and verification.
Pcon stands for power control intel 8051 microcontroller register. In this tutorial, we will take a look at the 8051 microcontroller special function registers or sfrs. Some of the operations where the accumulator is used are. Pcon power control intel 8051 microcontroller register. Reset initializes the stack pointer to location 07h, and it is incremented once to start from location 08h, which is the first register r0 of the second register bank. Cleared when processor vectors to execute interrupt service routine located at program address 001bh.
This is useful since rather than checking the exact value of the timer you can just check if the tfx bit is set. Creating time delay using timers in 8051 microcontroller. Its bits are used for generating interrupts internal or external. In the diagram you can see the sfr for tcon register, the bits used for interrupt handling and the timer run and timer over flow bits.
Since we can use them as counters so we can easily generate timedelays and baud rate for serial uart communication. Know about types of registers in 8051 microcontroller. Apr 20, 2019 timer registers tcon timer control register tcon is an 8bit register. Generation of time delay is most important concept in embedded systems. How many bit addressable location are placed in internal ram. Both can be configured to operate either as timers or as event counters. Tmod timer mode register and tcon timer control register, which are. Microcontroller timers counters tmod tcon microcontroller. B122 digital electronics and microprocessors, microcontroller applications 2. Tcon timer control register with its individual bits and sfr.
The clock source for the time delay is the crystal frequency of 8051. Quite often, in microcontroller programming, there is a need to generate accurate delays as well as execute certain events periodically. Tmod timer mode register and tcon timer control register, which are used for activating and configuring timers and counters. Ie register interrupt enable register this is an 8 bit register used for enabling or disabling the interrupts. Nov 02, 2011 this bit in tmod register is used to know whether it is used as a delay generator or as an event counter. Tcon is also a 8 bit register used for the direct control of the timer operation. Tmod and tcon registers are used for setting and using these timerscounters.
Multiple choice questions and answers on microcontrollers and applicationspart1. The tcon then, by a rsds compatible column driver such as a samsung ks066 or a sharp lh168m. Tmod is an 8bit register used for selecting timer or counter and mode of timers. The accumulator is used to hold the data for almost all the alu operations. Dec 08, 2012 8051 timers counters jose borges,patricio lima, marcos brito, marek mastylo, jakub nyk group 4 deec mpi slideshare uses cookies to improve functionality and performance, and to provide you with relevant advertising. Counters and timers in 8051 microcontroller contain two special function registers. Registers of 80518031 microcontroller a media to get all. Since the 8051 has an 8bit architecture, each 16bit is accessed as two. Nov 30, 2017 the 8051 microcontroller special function registers are used to program and control different hardware peripherals like timers, serial port, io ports etc. Objective questions and answers on microcontrollers and applications. Whenever a timer overflows from it is highest value back to 0, the microcontroller automatically sets the tfx bit in the tcon register. Tr timer run and tf timer overflow bits which we use in almost all over timer applications are in it. Kavitha page 14 8051 makes use of two registers to deal with interrupts.
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. For example, once the serial port has been configured using scon, the program may read or write to the serial port using the sbuf register. It is an 8 bit register and each bit has a special function. The port 3 output buffers can sinksource four ttl inputs. The most important bits of the timer tr and tf are also in it. Tmod timer mode register and tcon timer control register, which are used for activating and configuring timers and counters timer mode control tmod. It then passes the control to the main program where it had left off. Each interrupt can be enabled or disabled by setting bits of the ie register. If you want to access the individual bits of the registers, you can access them by their names. A counter is a device that stores and sometimes displays the number of times a particular event or process occurred, with respect to a clock signal. Registers in 8051 math register indicates that each bit a of the register can be programmed. When the controller executes a subroutine, the tf flag is cleared.
How to use internal timer registers of 805189c51,89c52. Whenever the timercounter overflows, the tf flag is set to one. In the case of timers, register is incremented once every machine cycle. Tmod is an 8bit register where the lower 4 bits are set aside for timer 0 and the upper 4 bits are set aside for timer 1. Timercounter mode control tmod register, bits 2 and 6 respectively. Multiple choice questions and answers on microcontrollers and. The device is manufactured using atmels highdensity nonvolatile memory technology and is compatible with the industrystandard 80c51 instruction set and pinout. To select the operating mode and the timercounter operation of the timers we use tmod register. The tcon register has a 1bit flag, tf for each timer to indicate the timer overflow or. Tf is meant for denoting the end of each count 0000h to ffffh in the timer operation and set by the hardware on the timer overflow. Timer mode register set the various timer operation mode. You can also access whole register it self by its name.
As a result, microcontrollers are generally tailored for speci. Th1tl1 timer 1 16 bit register byte addressable only tcon. Operating mode selection register and tcon timercounter operation control register, higher and lower order bytes of individual timercounters. How is power control intel 8051 microcontroller register abbreviated. Most of the times, we need to generate precise time delay between two actions in any microcontroller applications. Tcon and tmod timer registers of 8051 microcontroller. In fact, by manipulating the 8051 microcontroller special function registers sfrs, you can assess or change the operating mode of the 8051 microcontroller. So you may have guessed something from the name itself special function registers known with an acronym sfr. Pcon is defined as power control intel 8051 microcontroller register very frequently. Both of these registers use the same register called tmod to set various timer operation modes. Microcontrollers notes for iv sem ecetce students saneesh. In this chapter, we will cover the details about the register configuration for the external interrupt in 8051 controllers.
On the other hand, the microcontroller incorporates all the features that are found in. Microchip offers digital potentiometer devices with typical endtoend resistances of 2. Dec 08, 2016 multiple choice questions and answers on microcontrollers and applicationspart1. Since costs are important, it is only logical to select the cheapest device that matches the applications needs. The second special function register is timer control register. It is used to count the events happening outside the microcontroller. So, upper nibble where there is for timer counter, lower nibble is for interrupt. Tcon timer control register 88h is sfr of tcon register tr0tr1. Serial port control and status register is the special function register scon.
The tcon register consists of timer overflow flags, timer run control bits, external interrupt flags and external interrupt type control bits. The tf flag is also used as an interrupt signal to initiate the execution of a subroutine. Then timer 0 will use tr1 timer1 register and tf1 timer1 flag i. The mcs51 architecture provides expansion in the form of a 64k external. Tcontimer control register 88h is sfr of tcon register tr0tr1. Special function registers ip, ie, tmod, tcon, scon, and pcon contain. A timer, when initiated, counts the internal clock pulses and thus the microcontroller can be made to execute something when it overflows. Shift registers are a type of sequential logic circuits that are mainly used for the storage of digital. In this project, i will discuss a little bit about timers in 8051 microcontroller and also how to generate a delay using 8051 timers. The 8051 has two counterstimers which can be used either as timer to generate a time delay or as counter to count events happening outside the microcontroller.
Cpu while a microcontroller is a single ic contains a cpu and much of remaining. How many io ports are placed in microcontroller 8051. Jun 26, 2018 quite often, in microcontroller programming, there is a need to generate accurate delays as well as execute certain events periodically. Timer 0 and timer 1 are two timer registers in 8051. Port 3 port 3 is an 8bit bidirectional io port with internal pullups.