Bei Mega64 u. 128
Code:
$regfile = "m64def.dat"
$crystal = 16000000 
$baud = 9600

Config Int2 = Falling
Config Int2 = Rising
Config Int2 = Low Level

Enable Int2

Do
Loop
;----------------------------------------------
;   Config Int2 = Falling
;----------------------------------------------
	LDS	r24,EICRA
	ANDI	r24,0xCF	; clear ISC20 +  ISC21 
;-------------------- !!!!!!!!!!!!!
	ORI	r24,0x10	; set   ISC20
;-------------------- !!!!!!!!!!!!!
	STS	EICRA,r24
;----------------------------------------------
; Config Int2 = Rising
;----------------------------------------------
	LDS	r24,EICRA
	ANDI	r24,0xCF	; clear ISC20 +  ISC21 
;-------------------- !!!!!!!!!!!!!
	ORI	r24,0x18	; set   ISC20 + ISC11
;-------------------- !!!!!!!!!!!!!

	STS	EICRA,r24

;----------------------------------------------
; Config Int2 = Low Level
;----------------------------------------------
	LDS	r24,EICRA
	ANDI	r24,0xCF	; clear ISC20 +  ISC21 
	ORI	r24,0x00	; none
	STS	EICRA,r24

;----------------------------------------------
; Enable Int2
;----------------------------------------------
	IN	r24,EIMSK
	ORI	r24,0x04
	OUT	EIMSK,r24
;----------------------------------------------
Do
Loop
;----------------------------------------------
L_0x00F2:
	JMP	L_0x00F2
Du siehst, in der Zeile stecken ev. Probleme
ORI r24,0x10 ; set ISC20
Er setzt das reserved-Bit

Und auch das stimmt nicht
ORI r24,0x18 ; set ISC20 + ISC11
Er hat statt ISC20 + ISC21 (rising)
den Flag ISC20 gesetzt (reserved)
und das falling-Bit vom INT1

Ob das tatsächlich probleme bringt, hängt vom Einzelfall ab.