Нашел вот такую штуку, как понял частотомер....
Хто-нибудь,пожалуйста, подпишите комментарии, чтоб уразуметь что к чему .....

$regfile = "m128def.DAT"
$crystal = 16000000
$baud = 9600

$hwstack = 32
$swstack = 16
$framesize = 40

Dim IsrFlag As Byte
Dim StartStamp As Word
Dim StopStamp As Word
Dim TimerTicks As Word
Dim FrequencyHz As Long

' ======================================================
' Timer1 configuration
'
' Mode: Normal mode
' Prescaler: 1 (No prescaler)
' Input capture: Falling edge / noise canceler enabled

TCCR1A=&H00
TCCR1B=&H81   ' &H01 will disable the noise canceler

Config PinD.4 = Input  ' Input capture pin (ICP1)
Set PortD4.0            ' Enable internal pull-up on the ICP1 pin.

' ======================================================

On Capture1 Timer1_capture_isr Nosave
Enable interrupts

Do

  IsrFlag = 0
  StartStamp = 0
  StopStamp = 0
  Timer1 = 0  ' Clear Timer1 count

  Set TIFR.ICF1  ' Clear Timer1 Input Capture Flag.
  Enable Capture1 ' Enable Input Capture interrupt.

  Waitms 10 ' During this time the signal is measured on the ICP1 pin.
             ' Here we wait 10 ms so we can measure down to 250 Hz.
             ' If the lowest frequency is 44.1 kHz, then wait for 100 ?s.

  Print "Start: " ; StartStamp ; "   Stop: " ; StopStamp

  TimerTicks = StopStamp - StartStamp
  Print "Timer Ticks: " ; TimerTicks

  FrequencyHz = 16000000 / TimerTicks  '16 MHz clock and no prescaler.
  Print "Frequency : " ; FrequencyHz ; " Hz"

  Waitms 1000
  Print "=========================================================="

Loop

End

'======================================================
' This interrupt service routine is triggered by a falling edge
' on the ICP1 pin.(PD4 of the ATbanned28).

Timer1_capture_isr:

!PUSH R16
!PUSH R17
!PUSH R26
!PUSH R27
!IN R16, SREG
!PUSH R16

'==============================

LOADADR IsrFlag , X
!LD R16, X

!sbrc R16,0 ' Skip next instruction if bit 0 in R16 is cleared.
!rjmp Timer1_capture_isr2

!SER R16  ' Set Flag (the variable IsrFlag is our flag)
!ST X, R16 ' Store the variable IsrFlag

LOADADR StartStamp , X 'Save Input Capture Register. (First falling edge).
!IN R16, ICR1L
!IN R17, ICR1H
!ST X+, R16
!ST X, R17

!rjmp Timer1_capture_isr3

'==============================

Timer1_capture_isr2: 'This was the second falling edge

!LDS R16,TIMSK 'Disable capture interrupt
!ANDI R16,&HDF
!STS TIMSK,R16

LOADADR StopStamp , X   'Save Input Capture Register
!IN R16, ICR1L
!IN R17, ICR1H
!ST X+, R16
!ST X, R17

Timer1_capture_isr3:

!POP R16
!OUT SREG, R16
!POP R27
!POP R26
!POP R17
!POP R16

Return

'=====================================================