815081695-CS3691-Embedded-Systems-and-IoT.pptx

To learn the internal architecture and programming of an embedded processor.
To introduce interfacing I/O devices to the processor.
To introduce the evolution of the Internet of Things (IoT).
To build a small low-cost embedded and IoT system using Arduino/Raspberry Pi/ open platform.
To apply the concept of Internet of Things in real world scenario.

1. CS3691 Embedded Systems and IoT

2. UNIT I 8-BIT EMBEDDED PROCESSOR   8-Bit Microcontroller – Architecture – Instruction Set and Programming – Programming Parallel Ports – Timers and Serial Port – Interrupt Handling. UNIT II EMBEDDED C PROGRAMMING   Memory And I/O Devices Interfacing –Programming Embedded Systems in C – Need For RTOS Multiple Tasks and Processes – Context Switching – Priority Based Scheduling Policies.

3. UNIT III : IOT AND ARDUINO PROGRAMMING   Introduction to the Concept of IoT Devices – IoT Devices Versus Computers – IoT Configurations – Basic Components – Introduction to Arduino – Types of Arduino – Arduino Toolchain – Arduino Programming Structure – Sketches – Pins – Input/Output From Pins Using Sketches – Introduction to Arduino Shields – Integration of Sensors and Actuators with Arduino. UNIT IV: IOT COMMUNICATION AND OPEN PLATFORMS IoT Communication Models and APIs – IoT Communication Protocols – Bluetooth – WiFi – ZigBee – GPS – GSM modules – Open Platform (like Raspberry Pi) – Architecture – Programming – Interfacing – Accessing GPIO Pins – Sending and Receiving Signals Using GPIO Pins – Connecting to the Cloud.

4. UNIT V: APPLICATIONS DEVELOPMENT   Complete Design of Embedded Systems – Development of IoT Applications – Home Automation– Smart Agriculture – Smart Cities – Smart Healthcare.

5. TEXTBOOK 1. Muhammed Ali Mazidi , Janice Gillispie Mazidi , Rolin D. McKinlay , “The 8051 icrocontroller and Embedded Systems”, Pearson Education, Second Edition, 2014 2. Robert Barton, Patrick Grossetete , David Hanes, Jerome Henry, Gonzalo Salgueiro , “ IoT Fundamentals: Networking Technologies, Protocols, and Use Cases for the Internet of Things”, CISCO Press, 2017. REFERENCES : 1. Michael J. Pont, “Embedded C”, Pearson Education, 2007. 2. Wayne Wolf, “Computers as Components: Principles of Embedded Computer System Design”, Elsevier, 2006. 3. Andrew N Sloss , D. Symes , C. Wright, “Arm System Developer’s Guide”, Morgan Kauffman/ Elsevier, 2006. 4. Arshdeep Bahga , Vijay Madisetti , “Internet of Things – A hands-on approach”, Universities Press, 2015

6. COURSE OBJECTIVES: To learn the internal architecture and programming of an embedded processor. To introduce interfacing I/O devices to the processor. To introduce the evolution of the Internet of Things ( IoT ). To build a small low-cost embedded and IoT system using Arduino /Raspberry Pi/ open platform. To apply the concept of Internet of Things in real world scenario.

7. What is a Microprocessor? It is a processing device that converts data into information based on some sets of instructions. It is a very compact electronic chip due to which it is referred to as the  microprocessor . OR A microprocessor is a computer processor for which the data processing logic and control is included on a single integrated circuit (IC), or a small number of Ics The microprocessor is used as the CPU ( Central Processing Unit ). A typical microprocessor consists of two major parts namely ALU ( Arithmetic Logic Unit ) and CU ( Control Unit ). Intel 8085 or 8086 processing chips are the examples of microprocessors.

8. What is a Microcontroller? A  microcontroller  is an electronic system which consists of a processing element, a small memory ( RAM ,  ROM ,  EPROM ), I/O ports, etc. on a single chip. In electronic systems such washing machines, air conditioners, refrigerators, etc., microcontrollers are used to automate the operation of the device based on user’s instructions.

9. S.No Microprocessor Microcontroller 1 Microprocessor acts as a heart of computer system. Microcontroller acts as a heart of embedded system. 2 It is a processor in which memory and I/O output component is connected externally. It is a controlling device in which memory and I/O output component is present internally. 3 Since memory and I/O output is to be connected externally. Therefore the circuit is more complex. Since on chip memory and I/O output component is available. Therefore the circuit is less complex. 4 It cannot be used in compact system. Therefore microprocessor is inefficient. It can be used in compact system. Therefore microcontroller is more efficient. 5 Microprocessor has less number of registers. Therefore most of the operations are memory based. Microcontroller has more number of registers. Therefore a program is easier to write. 6 A microprocessor having a zero status flag. A microcontroller has no zero flag. 7 It is mainly used in personal computers. It is mainly used in washing machines, air conditioners etc.

10. On the basis of architecture the types of microcontroller are:

11. Von Neumann architecture: In a Von Neumann architecture, instructions and data are stored in a single memory system . This memory is usually implemented as random access memory (RAM) and is connected to the CPU and I/O devices through a common bus. 

12.   Havard Architecture : Harvard architecture is a type of computer architecture that has separate memory spaces for instructions and data. In a Harvard architecture system, the CPU accesses instruction and data memory spaces separately, which can lead to improved performance.

13. Types of Microcontroller on the basis of Service Provider AVR microcontroller is developed by Atmel service provider. Peripheral Interface Controller

14. 8051 Microcontroller Architecture: 4 KB on-chip ROM (Program memory). 128 bytes on-chip RAM (Data memory). The 8-bit data bus (bidirectional). 16-bit address bus (unidirectional). Two 16-bit timers. Instruction cycle of 1 microsecond with 12 MHz crystal. Four 8-bit input/output ports. 128 user-defined flags. Four register banks of 8 bit each. 16-byte bit-addressable RAM. The general purpose registers are 32 each is 8-bit. 8051 has two external and three internal interrupts. 8051 microcontroller specifies some special function features like UARTs, ADC, Op-amp, etc. It has a 16-bit program counter and data pointer. Key features of the 8051 Microcontroller:

15. Arithmetic and Logic Unit (ALU): All arithmetic and logical functions are carried out by the ALU. Addition, subtraction with carry, and multiplication come under arithmetic operations. Logical AND, OR and EXOR come under logical operations. Program Counter(PC): A program counter is a 16-bit register . The basic function of program counter is to fetch the next instruction to be executed. The PC increments automatically, holding the address of the next instructio n. Accumulator (A) and B Registers: Registers are usually known as data storage devices. 8051 microcontroller has 2 registers, namely Register A and Register B. These registers are used to store the output of mathematical and logical operations. B register is mainly used for multiplication and division operation along with A register.

16. The Accumulator or Register A: is the most important and most used 8051 Microcontroller SFRs. The Accumulator is used to hold the data for almost all the ALU Operations. Some of the operations where the Accumulator is used are: Arithmetic Operations like Addition, Subtraction, Multiplication etc. Logical Operations like AND, OR, NOT etc. Data Transfer Operations (between 8051 and External Memory)

17. Stack pointer (SP): The stack pointer in the 8051 holds the 8-bits address at the top of the stack, it supports the LIFO(Last In First Out) and it can take a value of 00 to FFH. The stack can be accessed using PUSH and POP instructions. DPTR (Data pointer) Register: DPTR is a 16 bit register used to hold the 16 bit address of data memory. The 16 bit data pointer can also be used as two 8 bit data pointer namely DPH, DPL. 8 bit data pointer used to accessing RAM and SFR.

18. Bus  : Bus is a group of wires which uses as a communication canal or acts as means of data transfer. The different bus configuration includes 8, 16 or more cables. Therefore, a bus can bear 8 bits, 16 bits all together. Types of buses in 8051 Microcontroller: Let's see the two types of bus used in 8051 microcontroller: Address Bus : 8051 microcontrollers is consisting of 16 bit address bus. It is generally be used for transferring the data from Central Processing Unit to Memory. Data bus : 8051 microcontroller is consisting of 8 bits data bus. It is generally be used for transferring the data from one peripherals position to other peripherals.

19. Program Status Word Register (PSW): Program Status Word Register is also called as Flag Register and is one of the important Special function Register (SFRs). The PSW Register consists of Flag Bits, which help the programmer in checking the condition of the result and also make decisions. Flags are 1-bit storage elements that store and indicate the nature of the result that is generated by execution of certain instructions. The following image shows the contents of the PSW Register.

20. Parity Bit (P) This parity flag bit is used to show the number of 1s in the accumulator only. If the accumulator register contains an odd number of 1s, then this flag set to 1. If accumulator contains even number of 1s, then this flag cleared to 0. Overflow Flag (OV) This flag is set during ALU operations, to indicate overflow in the result. It is set to 1 if there is a carry out of either the D7 bit or the D6 bit of the accumulator. Overflow flag is set when arithmetic operations such as add and subtract result in sign conflict. Register Bank Select Bits (RS1 And RS0) These two bits are used to select one of four register banks of RAM. By setting and clearing these bits, registers R0-R7 are stored in one of four banks of RAM as follows. Program Status Word Register (PSW)…

21. General-Purpose Flag (F0) This is a user-programmable flag; the user can program and store any bit of his/her choice in this flag , using the bit address. Auxiliary Carry Flag (AC) It is used in association with BCD arithmetic. This flag is set when there is a carry out of the D3 bit of the accumulator. Carry Flag (CY) This flag is used to indicate the carry generated after arithmetic operations. It can also be used as an accumulator, to store one of the data bits for bit-related Boolean instructions. Program Status Word Register (PSW)…

22. Input/Output (I/O) Ports: The I/O ports of the 8051 microcontroller are used to interface with the outside world. The 8051 microcontroller has four ports, each of which can be configured as either input or output. The ports are named Port 0, Port 1, Port 2, and Port 3. Port 0 is an 8-bit bidirectional port that can be used to interface with external devices. Port 1 is also an 8-bit bidirectional port that can be used to interface with external devices . Port 2 is an 8-bit port that is used to interface with external memory devices. Port 3 is an 8-bit port that is used to interface with external interrupt sources. In addition to the four I/O ports, the 8051 microcontroller also has several other I/O pins, including the Reset pin, the XTAL1 and XTAL2 pins, and the ALE (Address Latch Enable) pin . These pins are used for various purposes, such as system reset, clock input, and address bus control.

23. Data Memory: The data memory of the 8051 microcontroller is used to store data that is used by the microcontroller during operation. The data memory can be either internal RAM or external RAM. The size of the data memory varies from 128 bytes to 256 bytes for internal RAM, and up to 64K bytes for external RAM. The data memory is divided into two sections: the general-purpose registers and the SFRs (special function registers). The general-purpose registers are used to store data during program execution, while the SFRs are used to control the operation of the microcontroller and to interface with external devices. Program Memory: The program memory of the 8051 microcontroller is used to store the program code that the microcontroller executes. The program memory can be either ROM or Flash memory. The size of the program memory varies from 2K to 64K bytes , depending on the specific model of the microcontroller.

24. SCON (Serial Control) Register: The Serial Control or SCON SFR is used to control the 8051 Microcontroller’s Serial Port. It is located as an address of 98H. SCON, control the Operation Modes of the Serial Port. SCON Register also consists of bits that are automatically SET when a byte of data is transmitted or received .

25. Power Control (PCON) Register: IDLE MODE: In this mode the clock is cut from the processor only, other parts of the microcontroller such as timers. In this mode 80% of power is saved. The 20% power is used to get the microcontroller from idle mode to normal mode.  POWER DOWN MODE: In this mode, clock supply is cut from the whole system. In this power saving mode maximum amount of power is saved.  The PCON register is used for power control and baud rate selection.It also consists of general purpose user flags.

26. TCON (Timer Control register): TCON is an 8-bit register. Its bits are used for generating interrupts internal or external. The most important bits of the timer TR and TF are also in it. TR (timer run) and TF (timer overflow) bits which we use in almost all over timer applications are in it.

27. TMOD (Timer Mode register): 8-bit register used to select timer mode. There are 4 modes in which timer can be loaded. 1. Mode 0 : 13-bit timer 2. Mode 1: 16-bit timer 3. Mode 2 : 8-bit auto reload 4. Mode 3 : Split timer mode TH0/TL0->Timer 0 :16 bit register (byte addressable only) 8 bits can be send at a time. TH1/TL1-> Timer 1: 16 bit register (byte addressable only) 8 bits can be send at a time. The TMOD register is used to select the operating mode and the timer/Counter operation. The Lower 4 bits used to control timer 0 and the upper two bits used to control timer 1. C/T – 0 TIMER - 1 Counter

28. IE (Interrupt Enable) Register: This register is responsible for enabling and disabling the interrupt. EA register is set to one for enabling interrupts and set to 0 for disabling the interrupts. Its bit sequence and their meanings are shown in the following figure.

29. IP (Interrupt Priority) Register: We can change the priority levels of the interrupts by changing the corresponding bit in the Interrupt Priority (IP) register as shown in the following figure.

30. A low priority interrupt can only be interrupted by the high priority interrupt, but not interrupted by another low priority interrupt. If two interrupts of different priority levels are received simultaneously, the request of higher priority level is served. If the requests of the same priority levels are received simultaneously, then the internal polling sequence determines which request is to be serviced.

31. Timer and Control Unit : The main function of a timer is to make a delay otherwise time gap among two events. This microcontroller includes two timers where each timer is 16-bit where the system can generate two delays concurrently to produce the suitable delay. The delay can be generated through the timer based on the requirement of the processor & transmits the signal to the processor whenever the particular delay gets generated.

32. Types of interrupt in 8051 Microcontroller: Timer 0 overflow interrupt - TF0 Timer 1 overflow interrupt - TF1 External hardware interrupt - INT0 External hardware interrupt - INT1 Serial communication interrupt - RI/TI

33. 8051 microcontroller Pin Diagram : 8051 microcontroller  is a 40 pin Dual Inline Package (DIP). These 40 pins serve different functions like read, write, I/O operations,  interrupts  etc., 8051 has four I/O ports wherein each port has 8 pins which can be configured as input or output depending upon the logic state of the pins. Therefore, 32 out of these 40 pins are dedicated to I/O ports. The rest of the pins are dedicated to VCC, GND, XTAL1, XTAL2, RST, ALE, EA’ and PSEN

34. Port 0 (P0.1 – P0.7) - Pin 32 to Pin 39 :  This is an 8-bit bidirectional input/output pins. The output drives and inputs buffers of port 0 are used to access external memory . Port 1 (P1.0-P0.7) - Pin 1 to Pin 8 –  Pin 1 to Pin 8 are assigned to Port 1 for simple I/O operations. They can be configured as input or output pins depending on the logic control i.e. if logic zero (0) is applied to the I/O port it will act as an output pin and if logic one (1) is applied the pin will act as an input pin . These pins are also referred to as P1.0 to P1. 7 // (where P1 indicates that it is a pin in port 1 and the number after ‘.’ tells the pin number i.e. 0 indicates first pin of the port. So, P1.0 means first pin of port 1, P1.1 means second pin of the port 1 and so on). These pins are bidirectional pins.// Port 2 (Pin 21 to Pin 28) –  Pin 21 to pin 28 are port 2 pins also referred to as P2.0 to P2.7. When additional external memory is interfaced with the 8051 microcontroller, pins of port 2 act as higher-order address bytes . These pins are bidirectional.

35. Port 3 (Pin 10 to Pin 17)–  Pin 10 to pin 17 are port 3 pins which are also referred to as P3.0 to P3.7. These pins are similar to port 1 and can be used as universal input or output pins. These pins are bidirectional pins. These pins also have some additional functions which are as follows: P3.0 (RXD) :   10th pin is RXD (serial data receive pin) which is for serial input. Through this input signal microcontroller receives data for serial communication. P3.1 (TXD) :  11th pin is TXD (serial data transmit pin) which is serial output pin. Through this output signal microcontroller transmits data for serial communication. P3.2 and P3.3 (INT0′, INT1′ ) :  12th and 13th pins are for External Hardware Interrupt 0 and Interrupt 1 respectively. When this interrupt is activated (i.e. when it is low), 8051 gets interrupted in whatever it is doing and jumps to the vector value of the interrupt (0003H for INT0 and 0013H for INT1) and starts performing Interrupt Service Routine (ISR) from that vector location. P3.4 and P3.5 (T0 and T1) :  14th and 15th pin are for Timer 0 and Timer 1 external input. They can be connected with 16 bit timer/counter. P3.6 (WR’) :  16th pin is for external memory write i.e. writing data to the external memory. P3.7 (RD’) :  17th pin is for external memory read i.e. reading data from external memory.

36. Pin 9 (RST) –  Reset pin. It is an active-high, input pin. Therefore if the RST pin is high for a minimum of 2 machine cycles , the microcontroller will reset i.e. it will close and terminate all activities. It is often referred as “power-on-reset” pin because it is used to reset the microcontroller to it’s initial values when power is on (high). Pin 18 and Pin 19 (XTAL2 And XTAL1) –  These pins are connected to an external oscillator which is generally a quartz crystal oscillator. They are used to provide an external clock frequency of 4MHz to 30MHz. Pin 20 (GND) –  This pin is connected to the ground. It has to be provided with 0V power supply. Hence it is connected to the negative terminal of the power supply. Pin 29 (PSEN) –  PSEN stands for Program Store Enable. It is output, active-low pin. This is used to read external memory . In 8031 based system where external ROM holds the program code, this pin is connected to the OE pin of the ROM.

37. Pin 30 (ALE/ PROG) –  ALE stands for Address Latch Enable. It is input, active-high pin. This pin is used to distinguish between memory chips when multiple memory chips are used . It is also used to de-multiplex the multiplexed address and data signals available at port 0 . During flash programming i.e. Programming of EPROM, this pin acts as program pulse input (PROG). Pin 31 (EA/ VPP) –  EA stands for External Access input. It is used to enable/disable external memory interfacing . In 8051, EA is connected to VCC as it comes with on-chip ROM to store programs. Pin 40 (VCC) –  This pin provides power supply voltage i.e. +5 Volts to the circuit.

38. Addressing modes of 8051 Immediate Addressing Mode Register Addressing Mode Direct Addressing Mode Register Indirect Addressing Mode Indexed Addressing Mode Implied Addressing Mode The way in which an operand is given to an instruction is known as addressing modes. Different addressing modes of the  8051 microcontrollers . In 8051 there are 1-byte, 2-byte instructions and very few 3-byte instructions are present. The opcodes are 8-bit long. As the opcodes are 8-bit data, there are 256 possibilities.

39. Immediate addressing mode : In this Immediate Addressing Mode, the data is provided in the instruction itself. The data is provided immediately after the opcode. These are some examples of Immediate Addressing Mode. MOV A, #0AFH; MOV R3, #45H; MOV DPTR, #FE00H In these instructions, the # symbol is used for immediate data. In the last instruction, there is DPTR. The DPTR stands for Data Pointer. Using this, it points the external data memory location

40. Register addressing mode : In the register addressing mode the source or destination data should be present in a register (R0 to R7). These are some examples of Register Addressing Mode. ADD A, Rn (This is general instruction). ADD A, R5 (This instruction will add the contents of register R5 with the accumulator contents). MOV A, R5; MOV R2, #45H;

41. Direct Addressing Mode : In the Direct Addressing Mode, the source or destination address is specified by using 8-bit data in the instruction. Only the internal data memory can be used in this mode. Here some of the examples of direct Addressing Mode. MOV A, 25H (This instruction will read/move the data from internal RAM address 25H and store it in the accumulator.) MOV R2, 45H

42. Register indirect addressing Mode In this mode, the source or destination address is given in the register. By using register indirect addressing mode, the internal or external addresses can be accessed . The R0 to R7 are used for 8-bit addresses, and DPTR is used for 16-bit addresses, no other registers can be used for addressing purposes. Let us see some examples of this mode. The instruction specifies the name of the register in which address of data is available MOV A,@R0 This instruction moves the data from the register whose address is in the R0 register into the accumulator. MOV 0E5H , @R0 ; MOV @R1 , 80H In the instructions, the @ symbol is used for register indirect addressing.

43. Indexed addressing mode: Offset (from accumulator) is added to the base index register (DPTR OR Program Counter) to form the effective address of the memory location. In this case; this mode is made for reading tables in the program memory. MOVC A, @ A + DPTR ( This instruction moves the data from the memory to accumulator; whose address is computed by adding the contents of accumulator and DPTR) MOVC A , @A + PC ;

44. Implied Addressing Mode: In the implied addressing mode, there will be a single operand. These types of instruction can work on specific registers only. These types of instructions are also known as register specific instruction. Here are some examples of Implied Addressing Mode. RLA ; SWAP A ;

45. Types of instructions:- Depending on operation they perform, all instructions are divided in several groups: Data Transfer Instructions Arithmetic Instructions Logic Instructions Data exchange Push and Pop Instructions Rotate and Swap Instructions Bit-oriented Instructions Branch Instructions

46. Data Transfer Instructions:- Data transfer instructions move the content of one register to another. The register the content of which is moved remains unchanged. Data can be transferred within the internal Memory/to and from external RAM. If they have the suffix “X” (MOVX), the data is exchanged with external memory.

47. Data Transfer Instructions…

48. Instruction to Access External Data Memory:

49. Arithmetic Instructions:

50. Mnemonics Description Bytes Instruction Cycles ADD A, Rn A A + Rn (Add register to Accumulator) 1 1 ADD A, direct A A + (direct) (Add direct byte to Accumulator) 2 1 ADD A, @Ri A A + @Ri(Add indirect RAM to Accumulator) 1 1 ADD A, #data A A + data (Add immediate data to Accumulator) 2 1 ADDC A, Rn A A + Rn + C (Add register to Accumulator with Carry) 1 1 ADDC A, direct A   A + (direct) + C (Add direct byte to Accumulator with Carry) 2 1 ADDC A, @Ri A A + @Ri + C (Add indirect RAM to Accumulator with Carry) 1 1 ADDC A, #data A A + data + C (Add immediate data to Acc with Carr) 2 1 SUBB A, Rn A A - Rn - C (Accumulator Subtract Register from Acc with borrow) 1 1 SUBB A, direct A A - (direct) - C (Subtract direct byte from Acc with borrow) 2 1 SUBB A, @Ri A A - @Ri - C (Subtract indirect RAM from ACC with borrow) 1 1 SUBB A, #data A A - data - C (Subtract immediate data from Acc with borrow) 2 1 DIV AB Divide A by B ( Divide A by B) A quotient B remainder 1 4 MUL  AB Multiply A by B ( Multiply A & B) A low byte (A*B) B high byte (A* B) 1 4 INCREMENT & DECREMNT INSTRUCTIONS INC A A A+1 ( Increment Accumulator) 1 1 INC Rn Rn Rn + 1 ( Increment register) 1 1 INC direct (direct) (direct) + 1 ( Increment direct byte) 2 1 INC @Ri @Ri @Ri +1 ( Increment direct RAM) 1 1 INC DPTR DPTR DPTR +1 ( Increment Data Pointer) 1 2 DEC A A A -1 ( Decrement Accumulator) 1 1 DEC Rn Rn Rn - 1 ( Decrement Register) 1 1 DEC direct (direct) (direct) - 1 ( Decrement direct byte) 2 1 DEC @Ri @Ri @Ri - 1 ( Decrement indirect RAM) 1 1 DA A Decimal Adjust (Decimal Adjust Accumulator) 1 1

51. Logic Instructions :

52. Bit Level Logical Instructions: Push and Pop Instructions:

53. Data Exchange instructions:

54. Programming Parallel Ports The 8051 microcontroller has four parallel I/O ports, each of 8-bits. So, it provides the user 32 I/O lines for connecting the microcontroller to the peripherals. The four ports are P0 (Port 0), P1(Port1),P2(Port 2) and P3 (Port3). Upon reset all the ports are output ports.

55. In order to make them input , all the ports must be set i.e a high bit must be sent to all the port pins. This is normally done by the instruction “SETB”. Ex: MOV A,#0FFH ; A = FF MOV P0,A ; make P0 an input port

56. PORT 0: Port 0 is an 8-bit I/O port with dual purpose. If external memory is used, these port pins are used for the lower address byte address/data (AD0-AD7), otherwise all bits of the port are either input or output. Unlike other ports, Port 0 is not provided with pull-up resistors internally ,so for PORT0 pull-up resistors of nearly 10k are to be connected externally as shown. ALE indicates whether P0 has address or data. When ALE = 0, it provides data D0-D7 and when ALE =1 it provides address and data

57. Port 1: Port 1 occupies a total of 8 pins (pins 1 through 8). It has no dual application and acts only as input or output port. In contrast to port 0, this port does not need any pull-up resistors since pull-up resistors connected internally. Upon reset, Port 1 is configured as an output port. To configure it as an input port, port bits must be set i.e a high bit must be sent to all the port pins. This is normally done by the instruction “SETB”. Ex: MOV A, #0FFH; A=FF HEX MOV P1, A; make P1 an input port by writing 1’s to all of its pins

58. Port 2: Port 2 is also an eight-bit parallel port. (pins 21- 28). It can be used as input or output port. As this port is provided with internal pull-up resistors it does not need any external pull-up resistors. Upon reset, Port 2 is configured as an output port. If the port is to be used as input port, all the port bits must be made high by sending FF to the port. For Ex: MOV A, #0FFH ; A=FF hex MOV P2, A ; make P2 an input port by writing all 1’s to it

59. PORT 3: Port3 is also an 8-bit parallel port with dual function. (pins 10 to 17). The port pins can be used for I/O operations as well as for control operations. The details of these additional operatio ns are given below in the table. Port 3 also do not need any external pull-up resistors as they are provided internally similar to the case of Port2 & Port 1. Upon reset port 3 is configured as an output port. If the port is to be used as input port, all the port bits must be made high by sending FF to the port. MOV A, #0FFH ; A= FF hex MOV P3, A ; make P3 an input port by writing all 1’s to it

60. TIMER’S CLOCK FREQUENCY AND ITS PERIOD In 8051-based system, the crystal oscillator has a frequency of 11.0592 MHz when C/T bit of TMOD is 0. Each machine cycle is made up of 12 clock cycles . Hence for a single machine cycle, the frequency becomes 1/12 × 11.0529 MHz = 921.6 KHz. For a single machine cycle, the time taken is T = 1/921.6 KHz = 1.085 us so the oscillator takes 1.085us for completing a single machine cycle.

61. MODE 0 : Mode 0 is exactly same like mode 1 except that it is a 13-bit timer instead of 16-bit. The 13- bit counter can hold values between 0000 to 1FFFH in TH-TL. Therefore, when the timer reaches its maximum of 1FFH, it rolls over to 0000, and TF is raised.

62. MODES OF OPERATION: MODE 1 : It is a 16-bit timer; therefore it allows values from 0000 to FFFFH to be loaded into the timer’s registers TL and TH as shown in Fig. After TH and TL are loaded with a 16-bit initial value, the timer must be started. We can do it by “SETB TR0 ” for timer 0 and “ SETB TR1 ” for timer 1. After the timer is started, it starts count up until it reaches its limit of FFFFH. When it rolls over from FFFF to 0000H , it sets high a flag bit called TFx (timer flag).

63. This timer flag can be monitored. When this timer flag is raised , one option would be stop the timer with the instructions “CLR TR0“ or CLR TR1 for timer 0 and timer 1 respectively. Again, it must be noted that each timer flag TF0 for timer 0 and TF1 for timer1. After the timer reaches its limit and rolls over, in order to repeat the process the registers TH and TL must be reloaded with the original value and TF must be reset to 0.

64. MODE 2 : It is an 8 bit timer that allows only values of 00 to FFH to be loaded into the timer’s register TH as shown in Figure. After THx is loaded with 8 bit value, the 8051 gives a copy of it to TLx . Then the timer must be started. It is done by the instruction “SETB TR0” for timer 0 and “SETB TR1” for timer1. This is like mode 1.

65. After timer is started, it starts to count up by incrementing the TLx register. It counts up until it reaches its limit of FFH. When it rolls over from FFH to 00, it sets high the TFx (timer flag). If we are using timer 0, TF0 goes high; if using TF1 then TF1 is raised. When TLx register rolls from FFH to 00 and TF is set to 1 , TLx is reloaded automatically with the original value kept by the THx register. To repeat the process, we must simply clear TFx and let it go without any need by the programmer to reload the original value . This makes mode 2 auto reload , in contrast in mode 1 in which programmer has to reload THx and TLx . MODE 2 …

66. MODE 3: Mode 3 is also known as a split timer mode . Timer 0 and 1 may be programmed to be in mode 0, 1 and 2 independently of similar mode for other timer. This is not true for mode 3 . Timers do not operate independently if mode 3 is chosen for timer 0. Placing timer 1 in mode 3 causes it to stop counting; the control bit TR1 and the timer 1 flag TF1 are then used by timer 0.

67. Example: Generate Delay =10ms with Clock frequency= 11.0592 MHz, using Timer 0 in mode1. Solution: Time delay=10ms; Clock frequency=11.0592 MHz Step 1: Divide the desired time delay by 1.085 us Count =10 ms /1.085 us= 9216 Step 2: Perform 65536 – n 65536-9216=56320= DC00H Step 3: Set TL = xx and TH = yy Here xx=DC and yy =00, Hence, TH0=DC and TL0=00.

68. The assembly code program to generate a delay of 10ms MOV TMOD, #01 ;Timer 0, mode 1, 16-bitmode HERE: MOV TL0, #00 ;TL0=0, the low byte MOV TH0,#0DCH ;TH0=DC, the high byte SETB TR0 ;Start timer 0 AGAIN: JNB TF0,AGAIN ;Monitor timer flag 0 CLR TR0 ;Stop the timer 0 CLR TF0 ;Clear timer 0 flag

69. Program to generate a square wave of 5 kHz frequency on pin P1.0, clock frequency =11.0592 MHz Given: Square wave frequency=5 kHz Clock frequency=11.0592 MHz Step 1: Calculate the Time delay T=1/f=1/5 kHz =0.2 ms T=0.2 ms which is the period of square wave T/2 =0.2/2=0.1 ms delay for high and low Step 2: Divide the desired time delay by 1.085 us Count=0.1ms/1.085 us = 92 Step 3: Perform 65536 – n TH0-TL0= 65536-92=65444= FFA4 H

70. MOV TMOD,#10 ;Timer 1, mode 1, 16-bitmode AGAIN : MOV TL1,#A4H ;TL1=A4, low byte of timer MOV TH1,#0FFH ;TH1=FF, the high byte SETB TR1 ; Start timer BACK: JNB TF1,BACK ;until timer rolls over CPL P1.0 ; compliment P1.0 CLR TR1 ;Stop the timer 1 CLR TF1 ;Clear timer 1 flag SJMP AGAIN ;Reload timer

71. Toggle LED connected at P1.0 with 5 microsec delay using timer1 and mode 2 MOV TMOD,#20 ;Timer 1 mode 2, 8-bit auto reload AGAIN: MOV TH1,#-5 ;TL1=256-5, low byte of timer SETB TR1 ;Start timer 1 BACK: JNB TF1, BACK ;until timer rolls over CPL P1.0 ; compliment P1.0 toggle LED CLR TF1 ; Stop the timer 1 SJMP BACK

72. Serial Ports in 8051 Microcontroller Microcontrollers can communicate data in either parallel form or serial form. In parallel communication, data is transferred over more than one wire for example if 8 wires of one microcontroller are connected to any other peripheral device or another microcontroller then at a particular time 8 data bits are transferred . On the other hand, in serial communication, data is transferred in bit by bit manner over a single wire. Serial communication is preferred when the distance between transmitter and receiver is large and it is required to save the cabling cost and reduce hardware complexity but definitely this comes at the cost of reduced speed of data transfer.

73. Fig. shows parallel data transmission Fig. shows serial data transmission In 8051 in built UART (Universal Asynchronous Receiver Transmitter) module performs the job of serial communication of data.

74. In 8051 microcontroller serial communication of data is performed with the help of following special purpose registers: SBUF (Serial buffer register) SCON (serial control register) TMOD (Timer mode register) TCON (Timer control register) TH1 (Timer1 register higher byte)

75. SBUF (Serial buffer register) : It is an 8-bit register and is used for serial communication of data in 8051 microcontroller. Whatever data is required to be transmitted via TXD line must be placed in the SBUF register. Similarly, the received data via RXD line is saved in SBUF register . When data is written to SBUF register then it is framed in between start and stop bit before it is transmitted via TXD line and similarly during reception of data start and stop bits are removed and actual data bits are extracted from the received frame and then it is placed in the SBUF register.

76. SCON (Serial Control) Register: The Serial Control or SCON SFR is used to control the 8051 Microcontroller’s Serial Port. It is located as an address of 98H. SCON, control the Operation Modes of the Serial Port. SCON Register also consists of bits that are automatically SET when a byte of data is transmitted or received .

77. Example: set baud rate at 9600 MOV TMOD, #20H ; timer 1,mode 2(auto reload) MOV TH1, #-3 ; To set 9600 baud rate SETB TR1 ; start timer 1 For the crystal oscillator frequency of 11.0592MHz the below given table can be used as a reference for getting the value that is required to be loaded into TH1 register for the desired baud rate generation. Baud Rate TH1 (Decimal) TH1 (Hex) 9600 -3 FD 4800 -6 FA 2400 -12 F4 1200 -24 E8

78. Write a program for the 8051 to transfer letter ‘A’ serially a 4800 baud rate continuously. MOV TMOD, #20H ; Timer 1, Mode 2 (Auto reload) MOV TH1, #-6 ; 4800 baud rate MOV SCON, #50H ; 8-bit, 1 stop, REN enabled SETB TR1 ; Star Timer 1 AGAIN: MOV SBUF, # “A” ; Letter A to be transferred HERE: JNB TI HERE CLR T1 ; Clear TI for next char SJMP AGAIN

79. Write a program to transfer the message “YES” serially at 9600 baud rate, 8-bit data, 1 stop bit. Do this continuously. MOV TMOD, #20H ;Timer 1, Mode 2 (Auto reload) MOV TH1, #FD ; 9600 baud rate MOV SCON, #50H ; 8-bit, 1 stop, REN enabled SETB TR1 ; Star Timer 1 AGAIN: MOV A, #”Y” ; transfer Y ACALL TRANS MOV A, #”E” ; transfer E ACALL TRANS MOV A, #”S” ; transfer S ACALL TRANS SJMP AGAIN TRANS: MOV SBUF, A ; Load SBUF HERE: JNB TI, HERE ; wait for last bit to transfer RET

80. Write a program for the 8051 to receive byte of data serially, and put them in P1. Set the 4800 baud rate, 8-bit data and 1 stop bit. MOV TMOD, #20H ;Timer 1, Mode 2 (Auto reload) MOV TH1, #-6 ; 4800 baud rate MOV SCON, #50H ; 8-bit, 1 stop, REN enabled SETB TR1 ; Star Timer 1 HERE: JNB RI, HERE ; wait for char to come MOV A, SBUF ;save incoming byte in A MOV P1, A ;sent to port 1 CLR RI ;get ready to receive next byte SJMP HERE