Difference between revisions of "AVR External Interrupts"
| Line 3: | Line 3: | ||
Steps to configure the Interrupts: | Steps to configure the Interrupts: | ||
| − | + | # Set Global Interrupt(I-bit) Enable bit in the AVR Status Register(SREG) | |
| + | # Set INT1 and INT0 bits in the General Interrupt Control Register (GICR) | ||
| + | # Configure MCU Control Register (MCUCR) to select interrupt type. | ||
| + | # Handle the interrupt in the Interrupt Service Routine code. | ||
=The Registers= | =The Registers= | ||
Revision as of 15:48, 19 March 2016
We have looked at the basics of AVR Interrupts, now let us go ahead and use the External Interrupts feature on the AVR MCUs.
Steps to configure the Interrupts:
- Set Global Interrupt(I-bit) Enable bit in the AVR Status Register(SREG)
- Set INT1 and INT0 bits in the General Interrupt Control Register (GICR)
- Configure MCU Control Register (MCUCR) to select interrupt type.
- Handle the interrupt in the Interrupt Service Routine code.
Contents
The Registers
General Interrupt Control Register (GICR)
| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
|---|---|---|---|---|---|---|---|
| INT1 | INT0 | INT2 | - | - | - | IVSEL | IVCE |
MCU Control Register (MCUCR)
| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
|---|---|---|---|---|---|---|---|
| SE | SM2 | SM1 | SM0 | ISC11 | ISC10 | ISC01 | ISC00 |
| ISC01 | ISC00 | Description |
|---|---|---|
| 0 | 0 | The low level of INT0 generates an interrupt request. |
| 0 | 1 | Any logical change on INT0 generates an interrupt request. |
| 1 | 0 | The falling edge of INT0 generates an interrupt request. |
| 1 | 1 | The rising edge of INT0 generates an interrupt request. |
General Interrupt Flag Register(GIFR)
| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
|---|---|---|---|---|---|---|---|
| INTF1 | INTF0 | INTF2 | - | - | - | - | - |
We will connect two switches to the two interrupt pins and show the status on a LCD. The connections are shown in the image below.