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Microcontroller 8051

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    • 1. Microcontroller 8051
    • 2. Contents:
      • Introduction
      • Block Diagram and Pin Description of the 8051
      • Registers
      • Memory mapping in 8051
      • Stack in the 8051
      • I/O Port Programming
      • Timer
      • Interrupt
    • 3. Why do we need to learn Microprocessors/controllers?
      • The microprocessor is the core of computer systems.
      • Nowadays many communication, digital entertainment, portable devices, are controlled by them.
      • A designer should know what types of components he needs, ways to reduce production costs and product reliable .
    • 4. Different aspects of a microprocessor/controller
      • Hardware :Interface to the real world
      • Software :order how to deal with inputs
    • 5. The necessary tools for a microprocessor/controller
      • CPU: Central Processing Unit
      • I/O: Input /Output
      • Bus: Address bus & Data bus
      • Memory: RAM & ROM
      • Timer
      • Interrupt
      • Serial Port
      • Parallel Port
    • 6. Microprocessors:
      • CPU for Computers
      • No RAM, ROM, I/O on CPU chip itself
      • Example : Intel’s x86, Motorola’s 680x0
      CPU General-Purpose Micro-processor RAM ROM I/O Port Timer Serial COM Port Data Bus Address Bus General-Purpose Microprocessor System Many chips on mother’s board General-purpose microprocessor
    • 7.
      • A smaller computer
      • On-chip RAM, ROM, I/O ports...
      • Example : Motorola’s 6811, Intel’s 8051, Zilog’s Z8 and PIC 16X
      RAM ROM I/O Port Timer Serial COM Port Microcontroller CPU A single chip Microcontroller :
    • 8.
      • Microprocessor
      • CPU is stand-alone, RAM, ROM, I/O, timer are separate
      • designer can decide on the amount of ROM, RAM and I/O ports.
      • expansive
      • versatility
      • general-purpose
      • Microcontroller
      • CPU, RAM, ROM, I/O and timer are all on a single chip
      • fix amount of on-chip ROM, RAM, I/O ports
      • for applications in which cost, power and space are critical
      • single-purpose
      Microprocessor vs. Microcontroller
    • 9.
      • Embedded system means the processor is embedded into that application.
      • An embedded product uses a microprocessor or microcontroller to do one task only.
      • In an embedded system, there is only one application software that is typically burned into ROM.
      • Example : printer, keyboard, video game player
      Embedded System
    • 10.
      • meeting the computing needs of the task efficiently and cost effectively
        • speed, the amount of ROM and RAM, the number of I/O ports and timers, size, packaging, power consumption
        • easy to upgrade
        • cost per unit
      • availability of software development tools
        • assemblers, debuggers, C compilers, emulator, simulator, technical support
      • wide availability and reliable sources of the microcontrollers.
      Three criteria in Choosing a Microcontroller
    • 11. Block Diagram CPU On-chip RAM On-chip ROM for program code 4 I/O Ports Timer 0 Serial Port OSC Interrupt Control External interrupts Timer 1 Timer/Counter Bus Control TxD RxD P0 P1 P2 P3 Address/Data Counter Inputs
    • 12.  
    • 13. Pin Description of the 8051  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 40 39 38 37 36 35 34 33 32 31 30 29 28 27 26 25 24 23 22 21 P1.0 P1.1 P1.2 P1.3 P1.4 P1.5 P1.6 P1.7 RST (RXD)P3.0 (TXD)P3.1 (T0)P3.4 (T1)P3.5 XTAL2 XTAL1 GND (INT0)P3.2 (INT1)P3.3 (RD)P3.7 (WR)P3.6 Vcc P0.0(AD0) P0.1(AD1) P0.2(AD2) P0.3(AD3) P0.4(AD4) P0.5(AD5) P0.6(AD6) P0.7(AD7) EA/VPP ALE/PROG PSEN P2.7(A15) P2.6(A14) P2.5(A13) P2.4(A12) P2.3(A11) P2.2(A10) P2.1(A9) P2.0(A8) 8051
    • 14. Pins of 8051 ( 1/4 )
      • Vcc ( pin 40 ):
        • Vcc provides supply voltage to the chip.
        • The voltage source is +5V.
      • GND ( pin 20 ): ground
      • XTAL1 and XTAL2 ( pins 19,18 )
    • 15. Figure (a). XTAL Connection to 8051
      • Using a quartz crystal oscillator
      • We can observe the frequency on the XTAL2 pin.
       C2 30pF C1 30pF XTAL2 XTAL1 GND
    • 16. Pins of 8051 ( 2/4 )
      • RST ( pin 9 ): reset
        • It is an input pin and is active high ( normally low ) .
          • The high pulse must be high at least 2 machine cycles.
        • It is a power-on reset.
          • Upon applying a high pulse to RST, the microcontroller will reset and all values in registers will be lost.
          • Reset values of some 8051 registers
    • 17. Figure (b). Power-On RESET Circuit 30 pF 30 pF 8.2 K 10 uF + Vcc 11.0592 MHz EA/VPP X1 X2 RST 31 19 18 9 
    • 18. Pins of 8051 ( 3/4 )
      • / EA ( pin 31 ): external access
        • There is no on-chip ROM in 8031 and 8032 .
        • The /EA pin is connected to GND to indicate the code is stored externally.
        • /PSEN & ALE are used for external ROM.
        • For 8051, /EA pin is connected to Vcc.
        • “ /” means active low.
      • /PSEN ( pin 29 ): program store enable
        • This is an output pin and is connected to the OE pin of the ROM.
    • 19. Pins of 8051 ( 4/4 )
      • ALE ( pin 30 ): address latch enable
        • It is an output pin and is active high.
        • 8051 port 0 provides both address and data.
        • The ALE pin is used for de-multiplexing the address and data by connecting to the G pin of the 74LS373 latch.
      • I/O port pins
        • The four ports P0, P1, P2, and P3.
        • Each port uses 8 pins.
        • All I/O pins are bi-directional .
    • 20. Pins of I/O Port
      • The 8051 has four I/O ports
        • Port 0 ( pins 32-39 ): P0 ( P0.0 ~ P0.7 )
        • Port 1 ( pins 1-8 ) : P1 ( P1.0 ~ P1.7 )
        • Port 2 ( pins 21-28 ): P2 ( P2.0 ~ P2.7 )
        • Port 3 ( pins 10-17 ): P3 ( P3.0 ~ P3.7 )
        • Each port has 8 pins.
          • Named P0.X ( X=0,1,...,7 ) , P1.X, P2.X, P3.X
          • Ex : P0.0 is the bit 0 ( LSB ) of P0
          • Ex : P0.7 is the bit 7 ( MSB ) of P0
          • These 8 bits form a byte.
      • Each port can be used as input or output (bi-direction).
    • 21. Hardware Structure of I/O Pin
      • Each pin of I/O ports
        • Internal CPU bus : communicate with CPU
        • A D latch store the value of this pin
          • D latch is controlled by “Write to latch”
            • Write to latch = 1 : write data into the D latch
        • 2 Tri-state buffer : 
          • TB1: controlled by “Read pin”
            • Read pin = 1 : really read the data present at the pin
          • TB2: controlled by “Read latch”
            • Read latch = 1 : read value from internal latch
        • A transistor M1 gate
          • Gate=0: open
          • Gate=1: close
    • 22. D Latch :
    • 23. A Pin of Port 1 8051 IC  P0.x D Q Clk Q Vcc Load(L1) Read latch Read pin Write to latch Internal CPU bus M1 P1.X pin P1.X TB1 TB2
    • 24. Writing “1” to Output Pin P1.X 8051 IC 2. output pin is Vcc 1. write a 1 to the pin 1 0 output 1 TB1 TB2 D Q Clk Q Vcc Load(L1) Read latch Read pin Write to latch Internal CPU bus M1 P1.X pin P1.X
    • 25. Writing “0” to Output Pin P1.X 8051 IC 2. output pin is ground 1. write a 0 to the pin 0 1 output 0 TB1 TB2 D Q Clk Q Vcc Load(L1) Read latch Read pin Write to latch Internal CPU bus M1 P1.X pin P1.X
    • 26. Reading “High” at Input Pin 8051 IC 2. MOV A,P1 external pin=High
      • write a 1 to the pin MOV P1,#0FFH
      1 0 3. Read pin=1 Read latch=0 Write to latch=1 1 TB1 TB2 D Q Clk Q Vcc Load(L1) Read latch Read pin Write to latch Internal CPU bus M1 P1.X pin P1.X
    • 27. Reading “Low” at Input Pin 8051 IC 2. MOV A,P1 external pin=Low
      • write a 1 to the pin
      • MOV P1,#0FFH
      1 0 3 . Read pin=1 Read latch=0 Write to latch=1 0 TB1 TB2 D Q Clk Q Vcc Load(L1) Read latch Read pin Write to latch Internal CPU bus M1 P1.X pin P1.X
    • 28. Other Pins
      • P1, P2, and P3 have internal pull-up resisters.
        • P1, P2, and P3 are not open drain.
      • P0 has no internal pull-up resistors and does not connects to Vcc inside the 8051.
        • P0 is open drain.
        • Compare the figures of P1.X and P0.X. 
      • However, for a programmer, it is the same to program P0, P1, P2 and P3.
      • All the ports upon RESET are configured as output.
    • 29. A Pin of Port 0 8051 IC  P1.x D Q Clk Q Read latch Read pin Write to latch Internal CPU bus M1 P0.X pin P1.X TB1 TB2
    • 30. Port 0 with Pull-Up Resistors P0.0 P0.1 P0.2 P0.3 P0.4 P0.5 P0.6 P0.7 DS5000 8751 8951 Vcc 10 K Port 0
    • 31. Port 3 Alternate Functions  17 RD P3.7 16 WR P3.6 15 T1 P3.5 14 T0 P3.4 13 INT1 P3.3 12 INT0 P3.2 11 TxD P3.1 10 RxD P3.0 Pin Function P3 Bit
    • 32. RESET Value of Some 8051 Registers: 0000 DPTR 0007 SP 0000 PSW 0000 B 0000 ACC 0000 PC Reset Value Register RAM are all zero. 
    • 33. Registers A B R0 R1 R3 R4 R2 R5 R7 R6 DPH DPL PC DPTR PC Some 8051 16-bit Register Some 8-bitt Registers of the 8051
    • 34. Memory mapping in 8051
      • ROM memory map in 8051 family
      4k DS5000-32 8k 32k from Atmel Corporation from Dallas Semiconductor 0000H 0FFFH 0000H 1FFFH 0000H 7FFFH 8751 AT89C51 8752 AT89C52
    • 35.
      • RAM memory space allocation in the 8051
      7FH 30H 2FH 20H 1FH 17H 10H 0FH 07H 08H 18H 00H Register Bank 0 (Stack) Register Bank 1 Register Bank 2 Register Bank 3 Bit-Addressable RAM Scratch pad RAM
    • 36. Stack in the 8051
      • The register used to access the stack is called SP (stack pointer) register.
      • The stack pointer in the 8051 is only 8 bits wide, which means that it can take value 00 to FFH. When 8051 powered up, the SP register contains value 07.
      7FH 30H 2FH 20H 1FH 17H 10H 0FH 07H 08H 18H 00H Register Bank 0 (Stack) Register Bank 1 Register Bank 2 Register Bank 3 Bit-Addressable RAM Scratch pad RAM
    • 37. Timer :
    • 38.  
    • 39. TMOD Register :
      • Gate : When set, timer only runs while INT(0,1) is high.
      • C/T : Counter/Timer select bit.
      • M1 : Mode bit 1 .
      • M0 : Mode bit 0.
    • 40. TCON Register:
      • TF1: Timer 1 overflow flag.
      • TR1: Timer 1 run control bit.
      • TF0: Timer 0 overflag.
      • TR0: Timer 0 run control bit.
      • IE1: External interrupt 1 edge flag.
      • IT1: External interrupt 1 type flag.
      • IE0: External interrupt 0 edge flag.
      • IT0: External interrupt 0 type flag.
    • 41. Interrupt :
    • 42. Interrupt Enable Register :
      • EA : Global enable/disable .
      • --- : Undefined .
      • ET2 : Enable Timer 2 interrupt.
      • ES : Enable Serial port interrupt.
      • ET1 : Enable Timer 1 interrupt.
      • EX1 : Enable External 1 interrupt.
      • ET0 : Enable Timer 0 interrupt.
      • EX0 : Enable External 0 interrupt .

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