' Pulse counter ' ============= ' ' ' Hardware connection : ' --------------------- ' 1. 3 X 7 segments display on PORTB<7:0> ' 2. 3 X PNP transistor on PORTA<3:0> to drive common anode ' of each 7 segments display ' ' ' Programming mode and PIC define ' ------------------------------- '

@ __config _HS_OSC & _WDT_ON & _PWRTE_ON ' HS oscillator ' Enable watch dog timer ' Enable power up timer ' DEFINE OSC 20 ' use 20 MHZ oscillator

' I/O Definition ' -------------- ' TRISA = %11111000 ' PORTA : <2:0> outputs to common Anode of 7 segment ' 1. PORTA.0 More significant ' 2. PORTA.2 Less significant ' : PORTA.4 input for signal

' TRISB = 0 ' PORTB connected to 7 segments ' B0 : segment a ' B1 : segment b ' B2 : segment c ' B3 : segment d ' B4 : segment e ' B5 : segment f ' B6 : segment g ' B7 : segment decimal dot

' Internal EEPROM definition ' -------------------------- ' data @0,192,249,164,176,153,146,130,248,128,144 ' table to convert ' numbers to 7 segments ' pattern output when ' drive invert

' Interrupt and register definition ' --------------------------------- ' OPTION_REG = %1111000 ' TMR0 clock source : RA4/T0CKI ' increment on low to high transition ' Prescaler assign to WDT ' WDT rate 1:1 ' INTCON = %10100000 ' Enable global interrupt ' Disable EE write interrupt ' Enable TMR0 overflow interrupt

' Variable definition ' ------------------- ' DisplayPort var PORTB ' Port for 7 Segments ClockInput var PORTA.4 ' Input pin for signal _7Seg1 con 14 ' enable more significant 7 segment display _7Seg2 con 13 ' enable mid significant 7 segment display _7Seg3 con 11 ' enable less significant 7 segment display Digit_1 var byte ' Hundreds digit Digit_2 var byte ' Tenth digit Digit_3 var byte ' Unit digit ToBeDisplay var word ' Result of count to be send to 7 segment display Display var byte ' Temp variable DisplayLoop var byte ' Delay var word ' Variable for Delay loop OverFlowVar var word ' Thousands var bit ' Flag for count >= 1000 & < 10 000 TenThousands var bit ' Flag for count >= 10 000

' Variable and software initialisation ' ------------------------------------ ' tobedisplay = 0 ' set initial value of count TMR0 = 0 ' reset prescaller on interrupt goto SetVarToBeDisplay MainLoop:

' MainLoop ' --------- ' ' 1. display the result of the count on RA4 pin ' 2. refresh display ' 3. reset Timer0 ' 4. reload prescaler. ' ' Duration of the procedure : 1 sec ' fine tuned by DelayBetweenEachDisplay Sub ' ' Looping 1 sec and get results of the pulse count in ' TMR0 + OverFlowVar ' DisplayRefresh:

' ' Testing amount of count ' ----------------------- ' ' Get the result of count and place decimal point flag ' on the according 7 segments ' If tobedisplay>=1000 then tobedisplay=tobedisplay/10 if tobedisplay>=1000 then tobedisplay=tobedisplay/10 Thousands=0 TenThousands=1 else TenThousands=0 thousands=1 endif else thousands=0 tenthousands=0 endif ' ' convert digit to 7 segment output pattern ' ----------------------------------------- display=ToBeDisplay dig 2 ' Read hundreds digit read display,digit_1 ' Convert hundreds

if thousands==1 then digit_1=digit_1 & $7F ' enable decimal dot ' by clearing PORTB.7

display=ToBeDisplay dig 1 ' Read tenths digit read display,digit_2 ' Convert tenths if tenthousands==1 then digit_2=digit_2 & $7F ' enable decimal dot ' ' by clearing PORTB.7 display=ToBeDisplay dig 0 ' Read units digit read display,digit_3 ' Convert units ' ' ' Send digit to 7 segments ' ------------------------ for displayloop = 0 to 111 ' loop for about 1 sec

' display hundreds ' ---------------- PORTA=_7seg1 ' enable hundreds 7 segment displayport=digit_1 ' display gosub DelayBetweenEachDigit ' display tenth ' ------------- PORTA=_7seg2 ' enable tenth 7 segment displayport=digit_2 ' display gosub DelayBetweenEachDigit ' display units ' ------------- PORTA=_7seg3 ' enable unit 7 segment displayport=digit_3 ' display gosub DelayBetweenEachDigit next tobedisplay = OverFlowVar + TMR0 OverFlowVar = 0 ' Reset OverFlowVar TMR0 = 0 ' reset prescaller goto DisplayRefresh

DelayBetweenEachDigit:

' DelayBetweenEachDigit ' --------------------- ' Produce delay of about 3 mSec ' ' Fine tuned with MPLAB StopWatch to get MainLoop = 1 sec '

for delay=1 to 307 @ nopnext@ nop@ nop@ nop

@ nop@ nop@ nop@ nop

return

disableSetVarToBeDisplay: ' ' SetVarToBeDisplay ' ----------------- ' interrupt routine of TMR0 overflow ' ' Reset prescaller ' Reset overflow flag ' OverFlowVar = OverFlowVar + 256 INTCON.2 = 0 ' clear overflow flag TMR0 = 0 ' reload TMR0 resume enable