Teachers Name : Suman Sarker Telecommunication Technology Subject Name : Microcontroller & Embedded System Subject Code : 6871 Semester : 7th Department : Electronics Ideal Institute Of Science & Technology (IIST)

LECTURE-10 CH-11 CH-11 INTERRUPT OF 8051

What is Interrupt?

What is Interrupt?

InterruptReading Remember Open Return to work

What is Interrupt? Interrupt Processing Remember current instruction address in Stack Register Execute ISR Return to work In terms of MCU

Types of Interrupt External / Hardware InterruptInternal / Software Interrupt Physical or interrupt from outsideADC, TIMER, USART etc.

External Interrupt

PIC 16F877A has the following 15 interrupt sources : 1)External 2)Timer 0 3)Timer 1 4)RB Port Change 5)Parallel Slave Port Read/Write 6)A/D Converter 7)USART Receive 8)USART Transmit 9)Synchronous Serial Port 10)CCP1 (Capture, Compare, PWM)PWM 11)CCP2 (Capture, Compare, PWM) 12)TMR2 to PR2 Match 13)Comparator 14)EEPROM Write Operation 15)Bus Collision The 5 registers that used to control the operation of Interrupts in PIC 16F877A Microcontroller : 1)INTCON 2)PIE1 3)PIR1 4)PIE2 5)PIR2

INTCON Register INTCON Register PIC 16F877A INTCON Register is a readable and writeable register which contains various enable and flag bits for External and Internal Interrupts. GIE – Global Interrupt Enable 1 – Enables all unmasked interrupts 0 – Disables all interrupts PEIE – Peripheral Interrupt Enable 1 – Enables all unmasked peripheral interrupts 0 – Disables all peripheral interrupts

TMR0IE – Timer 0 Overflow Interrupt Enable 1 – Enables the TMR0 interrupt 0 – Disables the TMR0 interrupt INTE – RB0/INT External Interrupt Enable 1 – Enables the RB0/INT external interrupt 0 – Disables the RB0/INT external interrupt RBIE – RB Port Change Interrupt Enable 1 – Enables the RB port change interrupt 0 – Disables the RB port change interrupt TMR0IF – Timer 0 Overflow Interrupt Flag 1 – TMR0 register has overflowed. It must be cleared in software. 0 – TMR0 register did not overflow INTF – RB0/INT External Interrupt Flag 1 – The RB0/INT external interrupt occurred. It must be cleared in software. 0 – The RB0/INT external interrupt did not occur

RBIF – RB Port Change Interrupt Flag 1 – At least one of the RB7 – RB4 pins changed state, a mismatch condition will continue to set the bit. Reading PORTB will end the mismatch condition and allow the bit to be cleared. It must be cleared in software. 0 – None of the RB7 – RB4 pins have changed state INTEDG bit of OPTION_REG Register is the Interrupt Edge Select bit. When it is 1 interrupt is on rising edge of RB0/INT pin and when it is 0 interrupt is on falling edge of RB0/INT pin.

External Interrupt

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