Intel ’ s x86: 8086,8088,80386,80486, Pentium Motorola ’ s 680x0: 68000, 68010, 68020,68030,6040
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• The embedded system is a combination of computer hardware,software additional electrical & mechanical parts• A computer is used in such devices primarily as a means to simplifythe system design and to provide flexibility.• Embedded systems employ the use of a RTOS (Real-TimeOperating System).
Microcontroller• A smaller computer.• On-chip RAM, ROM, I/O ports...• Example:- Motorola’s 6811, Intel’s 8051 and PIC 16X CPU RAM ROM A single chip Serial I/O Timer COM Port Port Microcontroller
The 8051 Microcontroller :• The 8051 is the first microcontroller of the MCS-51 family introduced by Intel Corporation at the end of the 1970’s.• The 8051 family characteristics: ○ The 8051 family characteristics: ○ 4K Bytes ROM ○ 128 Bytes RAM ○ two timer/counters (16 bit) ○ A serial port ○ 32 input/output port ○ Interrupt controller
IC 8051 Pin Description External memoryreset Add. Latch enable Program Store Enablecrystal
IC 8051 Daily Applications Digital clockMoving message display 7 segment display Traffic Light
IC 8051 Addressing Modes •Immediate addressing modes ADD A, #23h (Add immediate data to Acc) •Register addressing modes ADD A, R2 (Add register to Accumulator) •Direct addressing modes ADD A, 40h (Add data at location 40h to Accumulator) •Register Indirect addressing modes ADD A,@R2 (Add indirect RAM to Acc)
Interrupts in 8051 An interrupt is an external or internal event that interrupts the microcontroller to inform it that a device needs its service The advantage of interrupts is that the microcontroller can serve many devices (not all at the same time) Program Program Interrupt service time
Interrupts in 8051 EA - ET2 ES ET1 EX1 ET0 EX0 Internal Interrupts EX0 Enables or disables external interrupt ET0 Enables or disables timer 0 overflow interrupt EX1 Enables or disables external interrupt 1 ET1 Enables or disables timer 1 overflow interrupt ES Enables or disables the serial port interrupt ET2 Enables or disables timer 2 overflow or capture interrupt -- Not implemented, reserved for future use EA Disables all interrupts External Interrupts P3.2 :INT0 (external interrupt 0) P3.3 :INT1 (external interrupt 1)
General PurposeMicroprocessor• CPU for Computers• No RAM, ROM, I/O on CPU chip itself• Example--Intel’s x86: 8086,8088,80386,80486, Pentium Data Bus Many chips on mother CPU board General- Purpose Serial Micro- RAM ROM I/O Timer COM processor Port Port Address Bus General-Purpose Microprocessor System
The 8085 Microprocessor :• The features of INTEL 8085 are :• It is an 8 bit processor.• It is a single chip N-MOS device with 40 pins.• It has multiplexed address and data bus.(AD0-AD7).• It works on 5 Volt dc power supply.• The maximum clock frequency is 3 MHz while minimum frequency is 500kHz.• It provides 74 instructions with 5 different addressing modes.
IC 8085 Pin Description •AD0-AD7: Multiplexed Address and data lines. •A8-A15: Tri-stated higher order address lines. •ALE: Address latch enable is an output signal.It goes high when operation is started by processor . •S0,S1: These are the status signals used to indicate type of operation. •RD¯: Read is active low input signal used to read data from I/O device or memory. •WR¯: Write is an active low output signal used write data on memory or an I/O device.
IC 8085 Pin Description • READY: This an output signal used to check the status of output device.If it is low, µP will WAIT until it is high. • TRAP: It is an Edge triggered highest priority , non mask able interrupt. After TRAP, restart occurs and execution starts from address 0024H. • RST 5.5,6.5,7.5: These are maskable interrupts and have low priority than TRAP. • INTR¯&INTA: INTR is a interrupt request signal after which µP generates INTA or interrupt acknowledge signal. •IO/M¯: This is output pin or signal used to indicate whether 8085 is working in I/O mode(IO/M¯=1) or Memory mode(IO/M¯=0 ).
IC 8085 Pin Description •HOLD&HLDA: HOLD is an input signal .When µP receives HOLD signal it completes current machine cycle and stops executing next instruction. In response to HOLD µP generates HLDA that is HOLD Acknowledge signal. •RESET IN¯: This is input signal. When RESET IN¯ is low µp restarts and starts executing from location 0000H. •SID: Serial input data is input pin used to accept serial 1 bit data . •X1 & X2 : These are clock input signals and are connected to external LC,or RC circuit.These are divide by two so if 6 MHz is connected to X1X2, the operating frequency becomes 3 MHz. •VCC & VSS: Power supply VCC=+ -5Volt& VSS=-GND reference.
Arithmetic and Logical Group Accumulator: It is 8 bit general purpose register. It is connected to ALU. So most of the operations are done in Acc. Temporary register: All the arithmetic and logical operations are done in the temporary register but user can’t access it. Flag: It is a group of 5 flip flops used to know status of various operations done. The Flag Register along with Accumulator is called PSW or Program Status Word.
Arithmetic and Logical Group Flag is given by :S Z - AC - P - CY S: Sign flag is set when result of an operation is negative. Z: Zero flag is set when result of an operation is 0. Ac: Auxiliary carry flag is set when there is a carry out of lower nibble or lower four bits of the operation. CY: Carry flag is set when there is carry generated by an operation. P: Parity flag is set when result contains even number of 1’s. Rest are don’t care flip flops.
Register GroupTemporary registers (W,Z): These are not available for user. These are loaded only when there is an operation being performed.General purpose: There are six general purpose registers in 8085 namelyB,C,D,E,H,L These are used for various data manipulations.Special purpose : There are two special purpose registers in 8085:SP : (Stack Pointer) This is a temporary storage memory 16 bit register. Since there are only 6 general purpose registers, there is a need to reuse themPC: (Program Counter) It is 16 bit register used to point the location from which the next instruction is to be fetched.
IC 8085 Addressing modes Immediate addressing: Immediate data is transferred to address or register. Example : MVI A,20H Register addressing: Data is transferred from one register to other. Example : MOV A, C Indirect addressing: Data is transferred from address pointed by the data in a register to other register or vice-versa. Example: MOV A, M Implied addressing: These doesn’t require any operand. The data is specified in Opcode itself. Example: RAL: Rotate left with carry.
Interrupts in 8085 An interrupt is considered to be an emergency signal that may be serviced. The Microprocessor may respond to it as soon as possible.Interrupts can also be classified into: Maskable Interrupts (Can be delayed or Rejected) Non-Maskable Interrupts (Can not be delayed or Rejected)The 8085 has 5 interrupt inputs. The INTR input : INTR is mask-able using the EI/DI instruction pair. RST 5.5, RST 6.5, RST 7.5 : They are all mask-able. TRAP : is the only non-mask-able interrupt in the 8085
Interrupts in 8085The 8085 recognizes 8 RESTART instructions: RST0 - RST7 . Each of these would send the execution to a predetermined hard-wired memory location: Restart Instruction Equivalent to RST0 CALL 0000H RST1 CALL 0008H RST2 CALL 0010H RST3 CALL 0018H RST4 CALL 0020H RST5 CALL 0028H RST6 CALL 0030H RST7 CALL 0038H
Timing and State Diagram• The µP operates with reference to clock signal. The rise and fall of the pulse of the clock gives one clock cycle.• Each clock cycle is called a T state and a collection of several T states gives a machine cycle.• Important machine cycles are :5. Op-code fetch.6. Memory read.7. Memory write.8. I/Op-read.9. I/O write.
Timing and State Diagram Op-code fetch cycle :
Seven Segment Display Seven segments are electronic components that can be used to displaying alphanumeric characters, 7 LED are used (as shown in figure) and is designed from a dot-point with the size. pin configuration of seven segment
Seven Segment Display7 pins of the microcontroller are used to shape thecharacter of your LED display Port Relations Microcontroller with pin 7 Segment
Seven Segment Display Table 1. Configuring the Character 7 Segment Data
Software’s Used Top View ExpressKeil µVision Simulator PCB
Keil µVision IDE The µVision IDE from Keil combines project management, make facilities, source code editing, program debugging, and complete simulation in one powerful environment. The µVision development platform is easy-to-use and helping you quickly create embedded programs that work. The µVision editor and debugger are integrated in a single application that provides a seamless embedded project development environment.
Top View Simulator• Topview Simulator gives an excellent simulation environment for MCS 51 Microcontroller. A beginner can learn about 8051 based embedded solutions without any hardware. An experienced designer, you may find most of the required facilities built in the simulator that enabling you to complete your next project without waiting for the target hardware.
Express PCBExpress PCB allows you to designschematics and PCBs. It is idealfor those that are looking todesign anywhere from a two tofour layer circuit board.A drop and drag design allowsusers to pick the components ofthe circuit board and drop itonto the circuit board in thesoftware program. The designercan then place various pins in thecircuit board to show wherethings need to be connected.It also has the ability of theprogram to show the designerwhere there are flaws in theirdesign.
Express PCBThis way we can include resistors This way we can include different kind of IC’s
DC Motor interfacing withMicrocontrollersDC motors are always preffered over stepper motors.There are many things which we can do with our DC motor when interfaced with microcontroller.For example:we can control the speed of motor,we can control the direction of rotation,we can also do encoding of the rotation made by DC motor i.e. keeping track of how many turns are made by our motors etc. Usually H-bridge is preffered way of interfacing a DC motor.L293D is most used H-Bridge driver IC.
Working of H-Bridge The name "H-Bridge" is derived from the actual shape of the switching circuit which control the motion of the motor. It is also known as "Full Bridge". Basically there are four switching elements in the H-Bridge as shown
Truth Table For H-Bridge Truth Table High Left High Right Low Left Low Right Description Motor runs On Off Off On clockwise Motor runs Off On On Off anti- clockwise Motor stops On On Off Off or decelerates Motor stops Off Off On On or decelerates
Stepper MotorOf all motors, step motor is the easiest to control. Its handling simplicity is really hard to deny - all there is to do is to bring the sequence of rectangle impulses to one input of step controller and direction information to another input. Direction information is very simple and comes down to "left" for logical one on that pin and "right" for logical zero.Motor control is also very simple - every impulse makes the motor operating for one step and if there is no impulse the motor wont start. Pause between impulses can be shorter or longer and it defines revolution rate. This rate cannot be infinite because the motor wont be able to "catch up" with all the impulses (documentation on specific motor should contain such information)..