Nothing Special   »   [go: up one dir, main page]
Scribd Logo
Upload

Welcome to Scribd!

  • 40 views

    8051 Interrupts

    Uploaded by

    Bharath
    An interrupt is an external or internal event that interrupts the microcontroller to request service from a device. A microcontroller can service multiple devices through interrupts or polling. With interrupts, when a device needs service it sends a signal, the microcontroller interrupts its current task and services the device by running an interrupt service routine. With polling, the microcontroller continuously monitors devices for requests and services them in turn. Executing an interrupt involves saving state, jumping to an interrupt vector table to find the ISR, running the ISR, then returning to the interrupted task.

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd

    8051 Interrupts

    Uploaded by

    Bharath
    40 views16 pages
    An interrupt is an external or internal event that interrupts the microcontroller to request service from a device. A microcontroller can service multiple devices through interrupts or polling. With interrupts, when a device needs service it sends a signal, the microcontroller interrupts its current task and services the device by running an interrupt service routine. With polling, the microcontroller continuously monitors devices for requests and services them in turn. Executing an interrupt involves saving state, jumping to an interrupt vector table to find the ISR, running the ISR, then returning to the interrupted task.

    Original Description:

    Unit 5

    Copyright

    © © All Rights Reserved

    Available Formats

    PDF, TXT or read online from Scribd

    Did you find this document useful?

    Is this content inappropriate?

    An interrupt is an external or internal event that interrupts the microcontroller to request service from a device. A microcontroller can service multiple devices through interrupts or polling. With interrupts, when a device needs service it sends a signal, the microcontroller interrupts its current task and services the device by running an interrupt service routine. With polling, the microcontroller continuously monitors devices for requests and services them in turn. Executing an interrupt involves saving state, jumping to an interrupt vector table to find the ISR, running the ISR, then returning to the interrupted task.

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    40 views16 pages

    8051 Interrupts

    Uploaded by

    Bharath
    An interrupt is an external or internal event that interrupts the microcontroller to request service from a device. A microcontroller can service multiple devices through interrupts or polling. With interrupts, when a device needs service it sends a signal, the microcontroller interrupts its current task and services the device by running an interrupt service routine. With polling, the microcontroller continuously monitors devices for requests and services them in turn. Executing an interrupt involves saving state, jumping to an interrupt vector table to find the ISR, running the ISR, then returning to the interrupted task.

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    of 16

    INTERRUPTS

    • An interrupt is an external or internal event that


    interrupts the microcontroller to inform it that a device
    needs its service

    • A single microcontroller can serve several devices by two


    ways:
    1. Interrupt
    2. Polling

    2
    Interrupt
    – Upon receiving an interrupt signal, the
    microcontroller interrupts whatever it is doing
    and serves the device.
    – The program which is associated with the
    interrupt is called the interrupt service routine
    (ISR) .

    3
    Interrupt Vs Polling
    1. Interrupts
     Whenever any device needs its service, the device
    notifies the microcontroller by sending it an interrupt signal.
     Upon receiving an interrupt signal, the microcontroller interrupts
    whatever it is doing and serves the device.
     The program which is associated with the interrupt is called
    the
    interrupt service routine (ISR) or interrupt handler.
    2. Polling
     The microcontroller continuously monitors the status of a given
    device.
     When the conditions met, it performs the service.
     After that, it moves on to monitor the next device until every one is
    serviced.
    Steps in Executing an Interrupt
    1.It finishes the instruction it is executing and saves the address
    of the next instruction (PC) on the stack.
    2.It also saves the current status of all the interrupts internally
    (i.e: not on the stack).
    3.It jumps to a fixed location in memory, called the
    interrupt vector table, that holds the address of the ISR.
    4.The microcontroller gets the address of the ISR from
    the interrupt vector table and jumps to it.
    5.It starts to execute the interrupt service subroutine until
    it reaches the last instruction of the subroutine which is
    RETI (return from interrupt).
    6.Upon executing the RETI instruction, the microcontroller
    returns to the place where it was interrupted.
    Steps in executing an interrupt
    • Finish current instruction and saves the PC on stack.

    • Jumps to a fixed location in memory depend on type of


    interrupt

    • Starts to execute the interrupt service routine until


    RETI (return from interrupt)

    • Upon executing the RETI the microcontroller returns to the


    place where it was interrupted. Get pop PC from stack
    • Original 8051 has 6 sources of interrupts
    – Reset (RST)
    – Timer 0 overflow (TF0)
    – Timer 1 overflow (TF1)
    – External Interrupt 0 (INT0)
    – External Interrupt 1 (INT1)
    – Serial Port events (RI+TI)
    • {Reception/Transmission of Serial Character}
    8051 Interrupt Vectors

    8
    8051 Interrupt related Registers
    • The various registers associated with the use of
    interrupts are:

    – TCON - Edge and Type bits for External Interrupts 0/1

    – SCON - RI and TI interrupt flags for


    RS232 {SERIAL COMMUNICATION}

    – IE - interrupt Enable

    – IP - Interrupts priority
    9
    Enabling and Disabling an Interrupt
    • The register called IE (interrupt enable) that is
    responsible for enabling (unmasking) and disabling
    (masking) the interrupts.

    10
    Interrupt Enable (IE) Register

    --

    • EA : Global enable/disable.
    • --- : Reserved for additional interrupt hardware.

    MOV IE,#08h • ES : Enable Serial port interrupt.


    or
    SETB ET1
    • ET1 : Enable Timer 1 control bit.
    • EX1 : Enable External 1 interrupt.
    • ET0 : Enable Timer 0 control bit.
    • EX0 : Enable External 0 interrupt.

    11
    Interrupt Priority

    12
    Interrupt Priority (IP)
    Register

    Reserved
    PS PT1 PX1 PT0 PX0

    Serial Port
    Timer 1 Pin INT 0 Pin

    INT 1 Pin Timer 0 Pin


    Priority bit=1 assigns high priority
    Priority bit=0 assigns low priority

    13
    64
    8
    Thank you

    You might also like