ex18 - freqin2.bs2

proteus得一些经典例子

' {$STAMP BS2}
' ==============================================================================
'
' File...... Ex18 - FreqIn2.BS2
' Purpose... Frequency Input
' Author.... Parallax
' E-mail.... [e-mail]
' Started...
' Updated... 01 MAY 2002
'
'
' ==============================================================================
' ------------------------------------------------------------------------------
' Program Description
' ------------------------------------------------------------------------------
' This program monitors and displays the frequency of a signal on Pin 0.
' ------------------------------------------------------------------------------
' I/O Definitions
' ------------------------------------------------------------------------------
FreqPin CON 0 ' frequency input pin
' ------------------------------------------------------------------------------
' Constants
' ------------------------------------------------------------------------------
Convert CON $0200 ' input to uSeconds (BS2)
' Convert CON $00CC ' BS2sx
' Convert CON $00C0 ' BS2p
' ------------------------------------------------------------------------------
' Variables
' ------------------------------------------------------------------------------
pHigh VAR Word ' high pulse width
pLow VAR Word ' low pulse width
period VAR Word ' cycle time (high + low)
freq VAR Word ' frequency
' ------------------------------------------------------------------------------
' Program Code
' ------------------------------------------------------------------------------
Main:
PULSIN FreqPin, 0, pHigh ' get high portion of input
PULSIN FreqPin, 1, pLow ' get low portion of input
period = (pHigh + pLow) */ Convert ' calculate cycle width in uSecs
freq = 50000 / period * 20 ' calculate frequency
' display on DEBUG screen
DEBUG Home
DEBUG "Period...... ", DEC period, " uS ", CR
DEBUG "Frequency... ", DEC freq, " Hz ", CR
GOTO Main ' do it again
END