As mentioned earlier, the timer can count till 65536; therefore, the total number of counts by the timer are 65536-264=65272. What this means is that the timer gets a pulse every 1.08 microseconds and counts up for each pulse. The Program Counter (PC) is a 2-byte address which tells the 8051 where the next instruction to execute can be found in the memory. Note: To use the timers as counters you have to place 1 in the C/T bit and it will act as a counter. The TCON register is bit addressable and is places at the address 88H in the ROM. Isn’t it amazing how we humans have managed to alter everything around us, including the complexities of the human body, making us wonder will we be able to conquer the abstract concept of time? Working and Usage of JTAG? Extract the downloaded f... What is I2C: - Inter Integrated Circuit - Bidirectional Data Transfer - Half duplex (have only one data line) - Synchronous bus so dat... We strongly recommed you to see the previous tutorial to understand the basics of I2C bus communication. (b) The predecessor of the 8051 was the 8048, introduced in 1976. Step 5: Reset all the flags as the software does not reset them, Step 6: Redo all the steps to generate a delay of 14 seconds. What is trouble shooting ? Once it reaches this value, it overflows and tells the system that a specific time has elapsed. What is a Binary Coded Decimal (BCD... 1. It is an 8-bit special function register that is placed at the address 89H in the ROM space and is not bit addressable. Led’s Binary counter with 8051 (89c51,89c52) microcontroller The code for 8-bit counter is below only the change is in count variable because 8-bit counter can count up to 255. # include When it is executed, the next address of the program counter is popped from the stack top, and the value of SP is decremented by 2. Everything is taught from the basics in an easy to understand manner. We will be talking about the TCON register in great detail later. This loop repeats 200 times thanks to register R3 giving a total delay of 200 x 70.820 milliseconds= 14.16 seconds. Start from the basic concepts related to the working of general microprocessors and work upto coding the 8085 and 8086. The 8051 has no direct way to read the program counter. When using the timer/counter as a timer the registers THx and TLx increments... TMOD REGISTER:. Keeping time is important for humans, but what might come as a shock to you is that even machines need to monitor time to function correctly. A bibliophile who loves to travel and experience new cultures. Object Oriented Programming Interview Questions - ... Embedded C interview questions On C or C++. One of these registers is TMOD. A pre-scaler scales the clock pulses from the master clock that are sent into the timer. Timer/Counter Calculations and Program using 8051 M icrocontroller: The delay is the one of the important factors in the application software development. A free course on digital electronics and digital logic design for engineers. As mentioned earlier, the timer registers in 8051 are upward counters, increasing the value stored in them on each input clock signal. The primary use of this mode is to provide backward compatibility with older microcontrollers like 8048. Here is a big list of 8051 simulators available. When an overflow condition is reached, the value is changed to 1 from 0. Mode 3: In this mode, both T0 and T1 behave differently. The timers and counters are hardware components of the microcontroller , that are used in many applications to provide the accurate time delay with count pulses . Due to this, each loop generated a delay of 655272 x 1.085 microseconds=70.820 milliseconds. What this means is that each value in the 8-bit register can’t be changed independently. 3. In the case of the 8051 microcontrollers, the master clock frequency is divided by 12 and then fed into the timer. Why microcontroller used more than the microproces... What is Bit addressability in 8051 or any other mi... What does the size of address bus affect ? Always points to the address of the next instruction to be executed. We hope that reading this article helped you gain more insights on how timers/counters work and how to program them. Mode 2: This mode comes with an auto-reload function, which helps deal with the software overhead issue in mode 2. The Program Counter (PC) is a 2-byte address which tells the 8051 where the next instruction to execute can be found in the memory. When a value 1 loads into these registers, the timers start counting from the values which are inside them. 304 views This mode is beneficial when two timers and baud rate generation are required simultaneously. The 8051 Microcontroller and Embedded Systems Using Assembly and C | Muhammad Ali Mazidi, Janice Gillispie Mazidi, Rolin D. McKinlay | download | Z-Library. The only difference being this timer can only keep time till 70.7 milliseconds. T0 works as a two 8 bit counters. Mode 0: In this mode, both the timers act as 13-bit counters. This site uses Akismet to reduce spam. 8051 Program Counter Program Counter (PC) The only register that is not memory mapped in 8051. What is the danger in using shared memory? Related courses to Timers and Counters in 8051. Read our privacy policy and terms of use. Program counter (PC): The Program Counter (PC) is a 2-byte address which tells the 8051 where the next instruction to execute is found in memory. As it is an 8 bit counter, it counts from 00 to FFH. What’s the purpose of the TMOD and TCON registers in 8051? Note that the address in the program counter is a 16-bit value. Download the MPLab IDE and Compiler by clicking the link below for free Click here to download the MPLAB 2. The 8051 uses two registers to handle and control the working of the Timer registers. These timers, play the dual functions of being timers and counters. Step 2: Insert the values in timer 0 or timer 1 from where you want them to should start up counting. So you might be thinking if this timer is just counting pulses, how does it keep time? Then we swap nibbles of r7 and make OR operation with r6 so the upper and lower nibbles are duplicated Mov a, r7 ; get the content in acc Anl a, #0F0h ; mask lower bit Mov r6, a ; send it to r6 Swap a ; xchange upper and lower nibbles of acc Orl a, r6 ; OR operation Mov r6, a ; finally load content in r6 Statement 3: –treat r6-r7 and r4-r5 as two 16 bit registers. Whereas in the case of a counter, this signal is given by any input value. The other is TCON. PC is not always incremented by 1. This helps to increase the accuracy of time kept but decreases the range at the same time. (a) RAM (random access memory) and ROM (read-only memory). 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. This 8-bit register is divided into two 4-bit registers to manage T0 and T1, respectively. Now that the clock signal to the register is given by an external stimulus, it counts upwards for each clock pulse given by the external peripheral. In order place the Program and Data anywhere in the Address Space of the 8051 Microcontroller, you can use the ORG Directive. Since the 8051 microcontroller has an 8-bit architecture, these registers are divided into two parts TL (Lower 8-bits) and TH (Upper 8-bits) . It is important to note that PC isn’t always incremented by one. Its an easy to use tool. The 8051 has two timers: timer0 and timer1. The PIC family 16F has 14-bit program counters. Address bus in 8051 is 16 bit width so that to hold the address it needs to be 16 bit. We’ll take a detailed look into each of these modes after we cover the TCON register. Most people think that assemble level language is difficult; well it is, there is no doubt in that. A bibliophile who loves to travel and experience new cultures. Both these timers are 16-bit registers. The lower 4 bits manage the modes for Timer 0, and the higher four bits manage Timer 1. This is also the address from which the 8051 Microcontroller will start executing the code. Why do we have to use the 8051? Here’s another analogy to break down the concept even more. Step 4: Wait for the overflow condition by monitoring the TF flag in the TCON register. Unit Test Tools are in use today - Embedded C inte... Trade off - Embedded C interview Question. Since the PC is 16-bit width, 8051 can access program addresses from 0000H to FFFFH, a total of 6kB of code. Now that we have got TMOD out of the way lets go to the next control SFR which is used by timers, TCON. PC is not always incremented by 1. Decimal to Binary Coded Decimal (BCD) Conversion in C or C++, Download Install Setup MPLAB IDE and Compiler for FREE, I2C Bus Communication Protocol Tutorial with Example. In the case of the above program the first opcode is 7D, which is the code for moving an operand to R5. The 8051 Microcontroller program status word register, also referred to as the flag register, is an 8-bit register Not only this, but these timers also help optimize CPU utilization as they can generate delays independently. In this tutorial we will see how to convert the decimal number to a BCD and BCD to a decimal number. PC starts at 0000h when the 8051 initializes and is incremented every time after an instruction is executed. In the case of timers, this clock frequency is given by the pre-scaler (making it count upwards every 1.08 millisecond). Program counter contains the address of the next instruction. Each time P3.4 goes low, the 16-bit counter increments by 1. The most widely used registers of the 8051 are A (accumulator), B, R0-R7, DPTR (data pointer), and PC (program counter). Bit Manipulation and Byte Manipulation Embedded C ... Embedded C interview question - Write an iterative... Embedded C interview Question - TCB (w.r.t real-ti... Embedded C interview Questions - features supporte... Embedded C interview questions - How to switch fro... Embedded C interview question - What is Instructio... Embedded C interview question - What is the Main p... Interview Question - What are the various modes in... Interview Question - What is a start-up routine fo... Embedded C interview question - how to initialize ... Embedded C interview Questions - How to initialize... Embedded C Interview Question - What is the functi... What makes an OS a RTOS ? After execution of one instruction PC is incremented to point to the address of the next instruction to be executed. The timer starts at 0000H or any value inserted into the timer registers and begins counting up till FFFFH, which is 65536 in decimal. A directory of Objective Type Questions covering all the Computer Science subjects. Now this change in the value of TF1/TF0 flag will occur at regular intervals of time and can be used to generate accurate time delays. Now the for loop runs from 0 to 255 and statement P1=count outputs the counter value on the led’s connected at output. 00 to 99 counter programming by using 7 segment interfacing with 8051 and output simulation with Keil Embedded C program Proteus simulation. About the authorNischay KhannaAn Engineering Graduate with a specialization in Embedded systems, who loves to dabble with IoT automation cause switching lights on with switches is to mainstream. (c) The term "non-volatile" describes this property of ROM. We’ll get to that in this post too. Let us say the 8051 microcontroller runs on a frequency of 11.0592 MHz; this is divided by 12 and then fed to the timer. The program counter is 16 bits wide; This means that it can access program addresses 0000 to FFFFH, a total of 64k bytes of code; 8051 Microcontroller Program status word (PSW )Register. It is an 8-bit register that starts the timer and also contains the flag which gets updated when the timer overflows.Structure of TCON register (Located at 88H-SFR space). Input signals are taken from port 3.4 for timer 0 and port 3.5 for timer 1. TF1 and TF0 are timer flags that indicate overflow condition in timers 1 and timer 0 respectively. Embedded C interview ... Reentrant routines and what is their use ? In the case of a 16-bit program counter, the code space is 64K, 2 16 = 64K, which occupies the 0000 - FFFFH address range. PC starts at 0000h when the 8051 initializes and is incremented every time after an instruction is executed. So to make things easy, we will first list the steps which need to be done to configure the timer and then write the code for it. Step 3: Start the timer by setting the TR flag in the TCON register. | Boundary scans | Test... What are multicast, broadcast and point-to-point? When the 8051 is initialized PC always starts at 0000h and is incremented each time an instruction is executed. 3. Here’s how the entire process of generating delays or counting events takes place in the 8051 microcontrollers. (b) ROM retains its contents even when powered-off. And, the program counter … This is … Mode 1: In this mode, both the timers act as 16-bit timers, enabling them to count from 0000 to FFFFH.Most programmers use this mode due to its high counting capacity. You can unders... How do you troubleshoot timing based requirements ? This mode offers a smaller counter size and is similar to mode one discussed next. It is used to hold 16 bit address of internal RAM, external RAM or external ROM locations. The Digital counter with 8051 is achieved by programming the microcontroller as discussed above and by attaching a sensor system to it. You can test your program using an 8051 simulator. Programming the timers in the 8051 microcontroller. Perform subtraction between th… making it act as a counter. ANSWER. Let’s dive into their functions in more detail. The answer to this question is simple: As mentioned earlier the timers on the 8051 microcontroller are 16 bit in size. Hence, the timer receives a frequency of 11.0592/12= 921.6 kHz which is 0.00108 milliseconds or 1.08 microseconds. When the 8051 is powered up, the PC (program counter) has 0000 and starts to fetch the first opcode from location 0000 of the program ROM. Both timers are 16 bits wide. One issue of this mode is that the start value has to be put in the timer registers after each cycle increasing software overhead. Program counter contains the address of the next instruction. The higher bit (TH1/TH0) acts as a storage element that stores and inputs the value to the lower bits when they reset. When the 8051 is initialized PC always starts at 0000h and is incremented each time an instruction is executed. Whereas in the case of a counter, this signal is given by any input value. (a) The 8051 was introduced in 1980. All this theory might be making you feel a little lazy so let’s get down to some coding and spice things up. Note: due to the 16-bit size of timer registers the maximum value you can count up to is 65536 after which the timer is reset. 4. It is used to hold 16 bit address of internal RAM, external RAM or external ROM locations. The 8051 micro-controllers have a 16-bit program counter. Difference between 8 bit 16 bit and 32 bit micro c... 8051 Architecture - Features and Memory organization. The stack of the 8051 plays a crucial role in the transfer of control when it comes to call instructions. The 8051 Microcontroller Assembly Language Program will start assembling from the Program Memory Address 0000H. 5. The program counter in PIC12F is 12-bit. What this means is that they can count up from 0000 to 1FFFH. In the example mentioned below, we will try to generate a time delay of 14 seconds using mode 1, Now you might be wondering how do we know how much time delay this code generated? Hence, you get a timer that can keep time for a maximum time of 70.7 milliseconds and signals the programmer (via updating TF0/TF1 in TCON register) when it gets over. They can be used either as timers or as counters. Once the pulses reach the timer, it starts counting up from 0000 to FFFFH. Read the privacy policy for more information. Now that you have a basic understanding of how timers function on the 8051 microcontrollers let us dig deep into the various modes it has to offer. Each of these pulses from the pre-scaler increases the value in the register until it reaches its upper limit of FFFFH. This update occurs every 70.7 (65536x 1.08 milliseconds) millisecond when counting from 0000 to FFFFH. All rights reserved. The program counter in the PIC18 family is 21-bit. TCON stands for timer control and is used to send the control signals for the functioning of the timer. You will control the the counter using a DIP switch which is also interfaced to the 8051 chip. These four bits are Gate, C/T, M1, and M0.Structure of TMOD register (Located at 89H-SFR space). This is to alert the programmer that the overflow has taken place. Difference between continue and break keyword in C... Is it possible to declare a variable inside switch... Decimal to Binary Coded Decimal (BCD) Conversion i... Swap two numbers without third (aka) temporary var... What is volatile keyword and explain about it ? Multiple choice questions on Microprocessor topic Microcontroller 8051. To understand the functioning of timers, only the higher 4 bits need to be understood. 3.Program counter(PC): The Program Counter (PC) is a 2-byte address which tells the 8051 where the next instruction to execute is found in memory. The Program Counter (PC) The Program Counter (PC) is a 2-byte address which tells the 8051 where the next instruction to execute is found in memory. Labels: 8051 tutorials, embedded basics, embedded c, Embedded C interview questtions, embedded interview questions, Information Technology, theory Newer Post Older Post Home SoCs and microcontrollers have an independent timer in tandem with a clock on board. Contents of PC are placed on address bus to find and fetch the desired instruction. The contents of the program counter are pushed into the stack (lower byte first). Programming Counters in 8051 Microcontroller and displaying the counts in LCD DIFFERENCE BETWEEN TIMERS AND COUNTERS:. Lets move to I2C bus arbitratio... What is Delay function? and why is trouble shoo... What is end-to-end checksum and, why & where is it... What are the ways to achieve shared memory? Interrupt Service Routine (ISR) - Embedded C inter... Cache Memory Embedded C interview Question, What is concurrency - Embedded C interview Question. We will discuss how to set these modes in the next section. As mentioned earlier, the timer registers in 8051 are upward counters, increasing the value stored in them on each input clock signal. To give you an example we will be writing an assembly language code to count values on port 3.5 and show them on port 2. The 8051 microcontroller provides four different modes of operation, and a programmer can decide which mode to use according to their needs. But now that you have an idea of how timers work programming will be much easier.