$regfile = "m128def.dat"
$crystal = 16000000
'-----------------------
'--- port A config ----
Config Porta = Output
'--- port B config ----
Config Portb = Output
'--- port C config ----
Config Portc = Input
'--- port D config ----
Config Pind.0 = Input
Config Pind.1 = Input
Config Pind.2 = Input
Config Pind.3 = Output
Config Pind.4 = Input
Config Pind.5 = Input
Config Pind.6 = Input
'--- port E config ----
Config Porte = Input
'----------------------
Config Timer1 = Counter , Capture Edge = Rising , Noise Cancel = 1 , , Prescale = 1
Enable Timer1
Enable Capture1
Enable Ovf1
On Ovf1 Overflow_timer1
On Capture1 Edge_seeker
Enable Interrupts
'-----------------------
Do
!nop
Loop
End                     ' endless loop
'----------------------
edge_seeker:
'----pulse making------
!sbi   PORTa,1                                              ' make short pulse to indicate the good working to capture every edge.
!nop
!nop
!nop
!cbi   PORTa,1
!push  r17
!push  r18
!push r19
!push r20

!ldi r18,$bf
!ldi r20,$40
!in    r17,TCCR1B                                           ' from here I change the state of the ICES1 bit.
!mov r19,r17
!SBRC  r17,6       ' 0 becomes 1 and in case it was 1, I change it in 0.
!and  r19,r18
!SBRS  r17,6
!or   r19,r20
!out  tccr1b,r19
!pop r20
!pop r19
!pop r18
!pop r17

Return
'----------------------
Overflow_timer1:

!sbi  PORTa,0
!nop
!cbi  PORTa,0
Return

End