Delay using 8. 05. Electronic Circuits and Diagram- Electronics Projects and Design. Delay using 8. 05. The 8. 05. 1 microcontroller has two independent 1. Timer 0 and Timer 1 and this article is about generating time delays using the 8. Generating delay using pure software loops have been already discussed here but such delays are poor in accuracy and cannot be used in sensitive applications. Delay using timer is the most accurate and surely the best method.
A timer can be generalized as a multi- bit counter which increments/decrements itself on receiving a clock signal and produces an interrupt signal up on roll over. When the counter is running on the processor’s clock , it is called a “Timer”, which counts a predefined number of processor clock pulses and generates a programmable delay. When the counter is running on an external clock source (may be a periodic or aperiodic external signal) it is called a “Counter” itself and it can be used for counting external events. In 8. 05. 1, the oscillator output is divided by 1. Timer as the clock signal.
That means for an 8. MHz, the timer clock input will be 1. MHz. That means the the timer advances once in every 1u. S and the maximum time delay possible using a single 8. Delays longer than this can be implemented by writing up a basic delay program using timer and then looping it for a required number of time. We will see all these in detail in next sections of this article.
Timer Program Of 8051 Microcontroller
Designing a delay program using 8. While designing delay programs in 8. TH and TL registers forms a very important thing. Let us see how it is done. Assume the processor is clocked by a 1.
MHz crystal. That means, the timer clock input will be 1. MHz/1. 2 = 1. MHz. That means, the time taken for the timer to make one increment = 1/1. MHz = 1u. SFor a time delay of “X” u. S the timer has to make “X” increments. Let TH be the value value that has to be loaded to TH registed and TL be the value that has to be loaded to TL register.
Then, THTL = Hexadecimal equivalent of (6. X) where (6. 55. 36- X) is considered in decimal. Example. Let the required delay be 1. S (ie; 1m. S). That means X = 1. X = 6. 55. 36 – 1. FC1. 8That means THTL = FC1. Therefore TH=FC and TL=1.
8051 microcontroller - Tutorial on internal architecture, 8051 pin diagram,packaging, program and data memory organization, 8051 reset circuit & system clock. 8051 Timer 1 Mode 2 Example Program. This example program shows how to configure timer/counter 1 as an 8-bit timer. An interrupt service routine (ISR) is invoked each. Introduction and Tutorial on Timers used in 8051 Microcontroller with Programming. Presented by : AKASH GUPTA 111257 ANKIT SAHA 111340 2. Introduction TMOD Register Modes. 8051 Counter 0 Example Program. This example program shows how to configure timer/counter 0 as a 16-bit counter taking input from Port 3.4. Each time P3.4 goes low.
Intro: Prop Bomb Count Down Timer - Project Geek #1. This is a simple one day project that i have made from 8051 microcontroller. The project can be easily ported to. Delay using 8051 timer. The 8051 microcontroller has two independent 16 bit up counting timers named Timer 0 and Timer 1 and this article is about generating time. 13-bit Time Mode (mode 0) Timer mode '0' is a 13-bit timer. This is a relic that was kept around in the 8051 to maintain compatability with its predecesor, the 8048.
Program for generating 1m. S delay using 8. 05. The program shown below can be used for generating 1m.
S delay and it is written as a subroutine so that you can call it anywhere in the program. Also you can put this in a loop for creating longer time delays (multiples of 1m. S). Here Timer 0 of 8.
MODE1 (1. 6 bit timer). DELAY: MOV TMOD,#0.
B // Sets Timer 0 to MODE1 (1. Timer 1 is not used. MOV TH0,#0. FCH // Loads TH0 register with FCH.
MOV TL0,#0. 18. H // LOads TL0 register with 1. H. SETB TR0 // Starts the Timer 0. HERE: JNB TF0,HERE // Loops here until TF0 is set (ie; until roll over).
CLR TR0 // Stops Timer 0. CLR TF0 // Clears TF0 flag. RETThe above delay routine can be looped twice in order to get a 2m. S delay and it is shown in the program below.
MAIN: MOV R6,#2. D. LOOP: ACALL DELAY. DJNZ R6,LOOP. SJMP MAIN. DELAY: MOV TMOD,#0.
B. MOV TH0,#0. FCH. MOV TL0,#0. 18. H. SETB TR0. HERE: JNB TF0,HERE. RETFew points to remember while using timers. Once timer flag (TF) is set, the programmer must clear it before it can be set again. The timer does not stop after the timer flag is set. The programmer must clear the TR bit in order to stop the timer.
Once the timer overflows, the programmer must reload the initial start values to the TH and TL registers to begin counting up from. We can configure the desired timer to create an interrupt when the TF flag is set. If interrupt is not used, then we have to check the timer flag (TF) is set using some conditional branching instruction. Maximum delay possible using a single 8. The technique is very simple. Write up a delay subroutine with delay equal to half the time period of the square wave.
Make any port pin high and call the delay subroutine. After the delay subroutine is finished, make the corresponding port pin low and call the delay subroutine gain. After the subroutine is finished , repeat the cycle again. The result will be a square wave of the desired frequency at the selected port pin.
The circuit diagram is shown below and it can be used for any square wave, but the program has to be accordingly. Programs for different square waves are shown below the circuit diagram. Square wave generation using 8. KHz Square wave using 8. MOV P1,#0. 00. 00. B. MOV TMOD,#0. 00. B. MAIN: SETB P1.
ACALL DELAY. ACALL DELAY. SJMP MAIN. DELAY: MOV TH0,#0.
FEH. MOV TL0,#0. 0CH. SETB TR0. HERE: JNB TF0,HERE. SETB P1. 0. END 2 KHz Square wave using 8. MOV P1,#0. 00. 00. B. MOV TMOD,#0. 00. B. MAIN: SETB P1. ACALL DELAY. ACALL DELAY.
SJMP MAIN. DELAY: MOV TH0,#0. FCH. MOV TL0,#0. 18. H. SETB TR0. HERE: JNB TF0,HERE. END1. 0 KHz square wave using 8. MOV P1,#0. 00. 00. B. MOV TMOD,#0. 00.
B. MAIN: SETB P1. ACALL DELAY. ACALL DELAY. SJMP MAIN. DELAY: MOV TH0,#0. FFH. MOV TL0,#0. CEH. SETB TR0. HERE: JNB TF0,HERE.
Counter 0 Example Program. Home / File Download Area.
This example program shows how to configure timer/counter 0 as a 1. Port 3. 4. Each time P3.