Module 3.pptx Microcontrollers for 4th sem

1. MICROCONTROLLERS BEC405A Gahan A V Assistant Professor Department of Electronics and Communication Engineering Bangalore Institute of Technology

2. DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING BANGALORE INSTITUTE OF TECHNOLOGY Syllabus

3. 3 DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING BANGALORE INSTITUTE OF TECHNOLOGY Module 3

4. BANGALORE INSTITUTE OF TECHNOLOGY DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING Counters and Timers What are Timers and Counters in 8051? In the 8051 microcontroller, timers and counters are hardware features used to measure time intervals or count external events. •Timer: Used to generate time delays by counting the internal clock pulses. •Counter: Used to count external events or signals, like how many times a switch is pressed.

5. BANGALORE INSTITUTE OF TECHNOLOGY DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING

9. BANGALORE INSTITUTE OF TECHNOLOGY DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING Timers and Counters in 8051 – Concept and Operation Many microcontroller applications require counting external events or generating precise internal time delays. For example: •Measuring the frequency of a pulse train (external events) •Creating accurate time delays between two computer actions (internal timing) These tasks can be done using software loops, but using software for timing or counting keeps the processor busy, preventing it from performing other important tasks. To handle these tasks more efficiently, the 8051 microcontroller provides two 16-bit up counters: •Timer 0 (T0) •Timer 1 (T1) These can be programmed to function in two modes: 1.Timer Mode – counts internal clock pulses 2.Counter Mode – counts external pulses

10. BANGALORE INSTITUTE OF TECHNOLOGY DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING Register Details Each counter is divided into two 8-bit registers: •Timer Low Byte: TL0, TL1 •Timer High Byte: TH0, TH1 Together, TL and TH form a 16-bit register for counting. Control Registers The behavior of the timers and counters is controlled using special function registers: •TMOD (Timer Mode Control Register): • Controls the mode of operation for both Timer 0 and Timer 1. • Can be thought of as two separate 4-bit sections, each for one timer. •TCON (Timer/Counter Control Register): • The upper nibble (4 bits) contains control bits and overflow flags for the timers. • The lower nibble is used for managing external interrupts.

16. BANGALORE INSTITUTE OF TECHNOLOGY DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING Timer/Counter Interrupts in 8051 The 8051 microcontroller includes timers and counters to take care of timing and counting tasks without burdening the processor. This allows the CPU to focus on more important operations while the timer or counter works in the background.

19. BANGALORE INSTITUTE OF TECHNOLOGY DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING Timing in 8051 Microcontroller When a counter is configured to operate as a timer, it counts the internal clock frequency of the 8051's oscillator, which is divided by 12. For example, if the crystal oscillator frequency is 6.0 MHz, the timer clock will have a frequency of 500 kHz (i.e., 6,000,000 / 12). The timer clock is gated to the timer circuit through control logic as illustrated in Figure 3.11. To allow oscillator clock pulses to reach the timer, the following conditions must be met: •The C/T bit in the TMOD register must be set to 0, selecting timer operation (as opposed to counter operation). •The TRx bit in the TCON register must be set to 1, which enables the timer to run. •The GATE bit in the TMOD register must be 0, or the external interrupt pin INTx must be high (logic 1).

21. BANGALORE INSTITUTE OF TECHNOLOGY DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING When a counter is programmed to work as a timer, it counts internal clock pulses generated by the microcontroller's oscillator.

24. BANGALORE INSTITUTE OF TECHNOLOGY DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING Timer Modes in 8051 Microcontroller (Using TMOD Register) The timers in 8051 can operate in four different modes. These modes are selected using the M1 and M0 bits in the TMOD register. The 8051 microcontroller has four different timer modes that allow you to control the timing and counting functions. These timers can be used for various tasks like generating delays, counting events, or producing PWM (pulse-width modulation) signals.

30. BANGALORE INSTITUTE OF TECHNOLOGY DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING In the 8051 microcontroller, counting and timing are conceptually similar, but they differ based on the source of clock pulses used for incrementing the timers or counters. When used as a timer: •The 8051 timer receives clock pulses from the internal oscillator, specifically via a divide-by-12 circuit. This means the clock frequency to the timer is reduced by a factor of 12, so the timer ticks slower than the system's actual clock frequency. •This mode is typically used for generating delays or measuring time intervals. When used as a counter: •The 8051's counter can receive external pulses as its clock source, rather than using the internal oscillator. The input pulse for the counter is provided by an external signal. •Pin T0 (P3.4) is used to feed pulses to counter 0, and Pin T1 (P3.5) is used for counter 1.

32. BANGALORE INSTITUTE OF TECHNOLOGY DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING Why Program the 8051 in C Programming the 8051 microcontroller in C is quite popular because it makes writing code easier and more readable than using Assembly. Compilers generate hex files that can be loaded onto microcontrollers for two main reasons: 1.Limited On-Chip ROM: Microcontrollers typically have limited on-chip ROM, which restricts the amount of program code that can be stored. 2.Code Space Limitation: The code space available for the 8051 microcontroller is limited to 64KB.

35. BANGALORE INSTITUTE OF TECHNOLOGY DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING DATA TYPES AND TIME DELAY IN 8051 C • To create smaller hex files, it is essential for 8051 C programmers to understand the specific C data types that work best with the 8051 microcontroller. • A good grasp of these data types helps optimize code size, which is crucial for efficient programming. In this section, we will focus on the C data types that are most commonly used and most effective for the 8051 microcontroller.

36. BANGALORE INSTITUTE OF TECHNOLOGY DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING C data types for the 8051

37. BANGALORE INSTITUTE OF TECHNOLOGY DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING Unsigned char The 8051 is an 8-bit microcontroller, so the unsigned char data type fits perfectly for most operations.

39. BANGALORE INSTITUTE OF TECHNOLOGY DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING Signed Char

41. BANGALORE INSTITUTE OF TECHNOLOGY DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING Unsigned int

43. BANGALORE INSTITUTE OF TECHNOLOGY DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING Signed int

45. BANGALORE INSTITUTE OF TECHNOLOGY DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING sbit (Single Bit)

48. BANGALORE INSTITUTE OF TECHNOLOGY DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING Bit and sfr

52. BANGALORE INSTITUTE OF TECHNOLOGY DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING 8051 C program to send the ASCII hex values for characters 0, 1, 2, 3, 4, 5, A, B, C, D to Port P1 one by one

53. BANGALORE INSTITUTE OF TECHNOLOGY DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING Program to toggle Port P1 forever using the 8051 in C:

54. BANGALORE INSTITUTE OF TECHNOLOGY DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING 8051 C Program to Send Values of -4 to +4 to Port P1

55. BANGALORE INSTITUTE OF TECHNOLOGY DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING 8051 C Program to Toggle Bit 0 of Port P1 (50,000 times)

56. BANGALORE INSTITUTE OF TECHNOLOGY DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING Timing Delay

58. BANGALORE INSTITUTE OF TECHNOLOGY DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING 8051 C program to toggle bits of p1 continuously forever without delay

60. BANGALORE INSTITUTE OF TECHNOLOGY DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING Write an 8051 C program to toggle the bits of P1 port continuously with a 250 ms delay.

62. BANGALORE INSTITUTE OF TECHNOLOGY DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING Program to toggle bits of Port P0 and Port P2 continuously with a 250 ms delay.

64. BANGALORE INSTITUTE OF TECHNOLOGY DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING PROGRAMMING 8051 TIMERS The 8051 microcontroller has two 16-bit timers: Timer 0 and Timer 1. These timers can be used either as timers to generate time delays or as event counters.

77. BANGALORE INSTITUTE OF TECHNOLOGY DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING Mode 1 Programming

82. BANGALORE INSTITUTE OF TECHNOLOGY DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING Solution Explanation: The program you've written toggles Pin P1.5 using Timer 0 in Mode 1 (16-bit mode) to create a delay. Here's the breakdown of the steps that happen in the program: 1.TMOD Register Loading The TMOD register is loaded with #01H, configuring Timer 0 for Mode 1 (16-bit timer mode). This means Timer 0 will count from 0000H to FFFFH before it overflows back to 0000H. 2.Timer Load Values The values #0F2H and #FFH are loaded into the TL0 (low byte) and TH0 (high byte) registers, respectively. These initial values define the start count for Timer 0. The timer will begin counting from FFF2H and overflow to FFFFH. 3.Pin Toggle The P1.5 pin is toggled using the CPL P1.5 instruction. This flips the state of the pin (from high to low or low to high), producing a pulse at that pin. 4.Delay Subroutine Call The ACALL DELAY instruction calls the delay subroutine. This subroutine uses Timer 0 to generate the delay. After the subroutine completes, the program continues by jumping back to the main loop (SJMP MAIN).

83. BANGALORE INSTITUTE OF TECHNOLOGY DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING 5.Starting the Timer (DELAY Subroutine) In the DELAY subroutine, Timer 0 is started with the SETB TR0 instruction. This sets the TR0 bit, which begins the timer counting process. The timer counts clock pulses from the system's crystal oscillator. 6.Timer Counting and Overflow As Timer 0 counts, it moves through successive values, starting from FFF2H and counting up. When the timer reaches FFFFH, the next clock pulse causes the timer to roll over to 0000H, which sets the TF0 flag. 7.Waiting for Overflow (JNB TF0) The program uses the JNB TF0, WAIT_LOOP instruction to monitor the TF0 (Timer 0 Overflow) flag. This instruction causes the program to stay in the WAIT_LOOP until TF0 becomes 1, signaling that Timer 0 has overflowed. 8.Stopping the Timer and Clearing Flags Once the overflow occurs, Timer 0 is stopped using the CLR TR0 instruction, which clears the TR0 bit. The overflow flag TF0 is cleared with the CLR TF0 instruction to reset the timer and prepare it for the next cycle. 9.Repeating the Process The process is repeated. The TH0 and TL0 registers are reloaded with the same values (F2H and FFH), the timer is started again, and P1.5 continues to toggle with the delay.

94. BANGALORE INSTITUTE OF TECHNOLOGY DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING To generate a large time delay using the 8051 timer and calculate the values for Timer 0 in Mode 1, we need to break the delay into smaller steps. Let's go through the steps you outlined with more detailed explanations, assuming we want a time delay based on 35,000 clock cycles.

97. BANGALORE INSTITUTE OF TECHNOLOGY DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING Mode 2 Programming

114. BANGALORE INSTITUTE OF TECHNOLOGY DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING The Case of Gate = 1 in TMOD

117. BANGALORE INSTITUTE OF TECHNOLOGY DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING Serial Data Input/output • In modern multiprocessor and distributed systems, it is essential for computers to communicate with one another. • A cost-effective method of achieving this communication is through serial data transmission, where data is sent and received bit by bit.

156. BANGALORE INSTITUTE OF TECHNOLOGY DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING MAX232 Chip Overview for 8051 to RS232 Communication • The MAX232 chip from Maxim Integrated is used for converting RS232 signals to TTL voltage levels and vice versa, making it ideal for interfacing the 8051 microcontroller with RS232 connectors. • Since the RS232 standard uses voltage levels that are incompatible with modern microcontrollers like the 8051, the MAX232 ensures that the data can be properly transmitted and received by converting the voltage levels appropriately.

Module 3.pptx Microcontrollers for 4th sem

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