Revision as of 15:35, 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:

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.

@@ Line 6: / Line 6: @@
 =The Registers=
-==General Interrupt Control Register (GICR)==
+'''General Interrupt Control Register (GICR)'''
 {| class="table table-condensed table-bordered"
 |-
@@ Line 14: / Line 14: @@
 |}
-==General Interrupt Flag Register(GIFR)==
+'''MCU Control Register (MCUCR)'''
-==MCU Control Register (MCUCR)==
 {| class="table table-condensed table-bordered"
 |-
@@ Line 22: / Line 21: @@
 | SE||SM2|| SM1|| SM0||'''ISC11'''||'''ISC10'''|| '''ISC01'''||'''ISC00'''
 |}
 {| class="table table-condensed table-bordered"
@@ Line 36: / Line 34: @@
 |1||1||The rising edge of INT0 generates an interrupt request.
 |}
+'''General Interrupt Flag Register(GIFR)
+'''
+{| class="table table-condensed table-bordered"
+|-
+! 7!!6!!5!!4!!3!!2!!1!!0
+|-class="success"
+| '''INTF1'''||'''INTF0'''|| '''INTF2'''|| -|| -|| -|| -|| -
+|}