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CHAPTER 11 EXTERNAL INTERRUPT CIRCUIT 2 (LEVEL)
11.7 Program Example for External Interrupt Circuit 2
An example of programming external interrupt circuit 2 is given below.
■ Program Example for External Interrupt Circuit 2
● Processing specification
The external interrupt circuit 2 detects an "L" level signal input to the P00/INT20
/AN4 pin and generates
an interrupt.
● Coding example
DDR0 EQU 0001H ; Address of the port data direction register
ADEN EQU 0034H ; Address of the A/D enable register
EIE2 EQU 0036H ; Address of the external interrupt 2 control register
EIF2 EQU 0037H ; Address of the external interrupt 2 flag register
IF20 EQU EIF2:0 ; Definition of the external interrupt request flag bit
ILR3 EQU 007DH ; Address of the interrupt level setting register
INT_V DSEG ABS ; [DATA SEGMENT]
ORG 0FFE6H
IRQA DW WARI ; Interrupt vector setting
INT_V ENDS
;------------------------Main program--------------------------------------------------------------------------------
CSEG ; [CODE SEGMENT]
; Stack pointer (SP) is assumed to have been initialized.
:;
CLRI ; Disable interrupts.
CLRB IF20 ; Clear external interrupt request flag.
MOV ILR2,#11111110B ; Set interrupt level to 2.
MOV DDR0,#00000000B ; Set pin INT20
/AN4 to serve inputs only.
MOV ADEN,#00000000B ; Set pin INT20
/AN4 to enable external interrupt inputs.
MOV EIE2,#00000001B ; Enable external interrupt inputs to pin INT20
/AN4.
SETI ; Enable interrupts.
:
;------------------------Interrupt processing routine----------------------------------------------------------------
WARI MOV EIE2,#00000000B ; Disable external interrupt inputs to pin INT20
/AN4.
CLRB IF20 ; Clear external interrupt request flag.