Counting Timer0 and Timer1 overflows without any interrupt handler

[dw_picbasic]

Hi Darrel and Hendrick,
I'm still moving along dabbling with this project.
Since I have the 16F887A in a LABX-1 project board, and I had a 12F683 mounted in a bread-board, I decided for convenience to see if I can make another step in this project using the 12F683. I got the 32khz crystal up and running on Timer1. By loading a preset value into Timer1's hi-byte, I can initiate the the frequency counting gate and Timer1 will interrupt right at 1Sec. (close enough on my Oscope).
So then I moved to add using Timer0 as the counter for the external frequency.
I'm only playing with a max input frequency of 300Khz right now, so I can utilize the PICs internal oscillator.

The following code is my progress.
It doesn't yet have the step of capturing the remainder value within Timer0.
Just got the point of attempting to counting Timer0 overflows.
But since I added the Timer0 register settings, it appears that I can't shut off the Timer1 overflow no matter what I do. Its supposed to display the timer0 overflow count and then go into a forever loop. But it keeps popping back up to "Display_Results". So I suspect timer1 is still initiating the interrupt routine.

' Name        : Frequency Counter Clock in Timer0 - Gate with Timer1
' Compiler    : PICBASIC PRO Compiler 2.6
' Assembler   : PM or MPASM
' Target PIC  : PIC12F683
' Hardware    : 32.768khz crystal on OSC1-ISC2 for 1sec gate
' Oscillator  : 4MHz internal osc for PIC
' Keywords    :
' Language    : PICBASIC PRO
'  
'                     VDD --- 1|----|8--- vSS
'    GP5/TICKI/OSC1/CLKIN --- 2|----|7--- GP0/AN0/CIN+/ICSPDAT/ULPWU
' GP4/AN3/T1G/OSC2/CLKOUT --- 3|----|6--- GP1/AN1/CIN-/VREF/ICSPCLK
'            GP3/MCLR/VPP --- 4|----|5--- GP2/AN2/T0CKI/INT/COUT/CCP1
'------------------------------------------------------------------------ 
  
Include "modedefs.bas"  ' Include serial modes for LCD display
define osc 4
OSCCON = %01100100     ' internal oscillator at 4 MHZ runs the pic
CMCON0 = 7             ' Comparators off
ANSEL = 0              ' Set all digital
WPU    = 0             ' Internal pull-ups = off
GPIO   = %00000000     ' clear GPIO port
TRISIO = %00000100     ' All outputs except gpio.2 (input to frequency)
CCP1CON=0              ' ccpm module off

LCD var GPIO.1			'use GPIO1 pin 6 to LCD display
GATE var byte            'variable for 1 second gate flag
TMR_CNT var word         'variable for counting timer0 overflows

on interrupt goto TMR1_INT

'setup Timer0 option_register
OPTION_REG = %10100111   'bit 7 pullups disabled
                         'bit 6 don't care 
                         'bit 5 Transition on TOCKI pin
                         'bit 4 Increment on low to high TOCKI pin
                         'bit 3 Prescaller assigned to TIMER0
                         'bit 2-0 Prescaller setting 1:256
INTCON.2 = 0		     'set Timer0 ovrflow flag zero
TMR0 = 0                 'clear the Timer0 counter register

'clear Timer1 interrupt registers
T1CON.0 = 0    'TMR1ON disable interrupts for now
TMR1L = 0      'clear lower 8 bits of Timer1 counter
INTCON = 0     'clear the system interrupt control register
PIR1 = 0       'clear the system interrup flag bits register
PIE1 = 0       'clear perephrial interrupt enable register

pause 1000

'configure Timer1 interrupt settings
T1CON.3 = 1     'T1OSC of the T1CON register enabled
PIE1.0 = 1		'Timer1 overflow enable bit enabled
INTCON.6 = 1	'Perephrial enable bit set to enable
INTCON.7 = 1    'GIE Global interrupt enable bit enabled
T1CON = 14		'T1OSCEN enable
                'T1Sync disabled
                'TMR1CS external source for Timer1
TMR1H = 207     'preload hi-byte of Timer1 counter so 
                'when interrupt occurs with 32khz crystal
                'on OSC1 + OSC2, it will be 1 second
T1CON.0 = 1     'T1CON.TMR1ON Timer1 enabled *NOW*

GATE = 1

main:
while GATE > 0       'After 1 Second Gate interrupt this ends
@ BTFSC INTCON,2    ;Test Timer0 overflow flag bit
@ incf _TMR_CNT,f   ;If flag set then increment TMR_CNT by 1
@ BTFSC INTCON,2    ;Test Timer0 overflow flag bit again
@ BCF INTCON,2      ;If flag set then clear it
wend

Display_Results:
serout LCD,T9600, [#TMR_CNT] 
pause 2000
loop_here:
goto loop_here

' ************ TIMER1 GATE INTERRUPT ROUTINE AFTER 1 SEC **************
disable
TMR1_INT:
GATE = 0
T1CON.0 = 0    'TMR1ON disable interrupts for now
INTCON = 0     'clear the system interrupt control register
PIR1 = 0       'clear the system interrup flag bits register
PIE1 = 0       'clear perephrial interrupt enable register
INTCON.2 = 0   'set Timer0 ovrflow flag zero
INTCON.7 = 0   'GIE OFF - Turn off all Interrupts
resume         'goto main

	 
End

[Darrel Taylor]

For this project ... you should not be using interrupts.
Especially not ON INTERRUPT. There's no guaranteed timing with ON INTERRUPT.

207 isn't a good value to load in the Timer.
Since the Timer will normally overflow in 65536 counts, you just need to set bit-7 of the high byte to make it overflow in 32768 counts.
With a 32768 Hz crystal, it will overflow in exactly 1 second.

Timer1 doesn't free-run. You need to stop and start it so that you can synchronize the Timer0 Gate output with Timer1's 1 second window.

Since the PIC's changed now, the oscillator's changed and interrupts are introduced ...
I think I'll just post my code for the 877A simulation in post #5.
Hopefully you can convert it for your needs with a different PIC.

; DT_FREQy.pbp
;
; Created     : Mon Feb 3 2014
; Processor   : PIC16F877A
; Compiler    : PicBasic Pro 3.0

;----[Device Configuration]--(See manual section 4.9)---------------------------
#CONFIG
  __config  _HS_OSC & _WDT_OFF & _PWRTE_OFF & _BODEN_OFF & _LVP_OFF & _CPD_OFF & _WRT_OFF & _DEBUG_OFF & _CP_OFF
#ENDCONFIG

;----[DEFINEs]------------------------------------------------------------------
DEFINE OSC 20

DEFINE LCD_DREG PORTD         ; LCD data port
DEFINE LCD_DBIT 4             ; LCD data starting bit 0 or 4
DEFINE LCD_RSREG PORTD        ; LCD register select port
DEFINE LCD_RSBIT 2            ; LCD register select bit
DEFINE LCD_EREG PORTD         ; LCD enable port
DEFINE LCD_EBIT 3             ; LCD enable bit
DEFINE LCD_BITS 4             ; LCD bus size 4 or 8
DEFINE LCD_LINES 2            ; LCD Number lines on LCD
DEFINE LCD_COMMANDUS 2000     ; LCD Command delay time in us
DEFINE LCD_DATAUS 50          ; LCD Data delay time in us

;----[Aliases]------------------------------------------------------------------
Timer1    VAR WORD EXT : @Timer1 = TMR1L
TMR0IF    VAR INTCON.2
TMR0CS    VAR OPTION_REG.5
TMR1IF    VAR PIR1.0
TMR1CS    VAR T1CON.1         ; Timer1 Clock Source Select bit
T1OSCEN   VAR T1CON.3         ; Timer1 Oscillator Enable Control bit
TMR1ON    VAR T1CON.0         ; Timer1 On bit
T1OSI     VAR PORTC.1         ; 32768 Hz input pin
PSCLKOUT  VAR PORTA.3         ; pin to clock out the remaining prescaler
PSA       VAR OPTION_REG.3    ; Prescaler Assignment bit

;----[Variables]----------------------------------------------------------------
Result     VAR WORD[2]        ; Final 32-bit Frequency measurement
T0overflow VAR Result[1]      ; Counts Timer0 overflows (HighWord of the result)
T0value    VAR Result.BYTE1   ; Final Timer0 value
PScount    VAR Result.BYTE0   ; Final Timer0 Prescaler value

FreqHigh   VAR WORD           ; Top five digits of the decimal result
FreqLow    VAR WORD           ; Bottom 3 digits of the decimal result
MeasCount  VAR WORD           ; Counts number of measurements

;----[Initialize]---------------------------------------------------------------
ADCON1 = 7                    ; All Digital
CMCON  = 7
T1OSCEN = 1                   ; Start Timer1 oscillator
PAUSE 250                     ; LCD Power-Up delay 
LCDOUT $FE,1,"DT's FREQy"
MeasCount = 0                 ; clear the measurement count

;----[Main Program Loop]--------------------------------------------------------
Main:
    GOSUB MeasureFreq         ; Get a Frequency Measurement
    GOSUB DisplayFreq         ; Display the Frequency

    MeasCount = MeasCount + 1 ; increment and display measurement count
    LCDOUT $FE,$94,"Meas = ", DEC MeasCount
GOTO Main

;----[Measure frequency on T0CKI]-----------------------------------------------
MeasureFreq:
    LOW PSCLKOUT          ; prevent signal from getting to Timer0
    PSA = 0               ; Prescaler is assigned to the Timer0 module
    TMR0CS = 1            ; Transition on T0CKI pin
    TMR1CS = 1            ; Timer1 Clock source = T1CKI (T1OSC)
    TMR1ON = 0            ; Stop Timer1
    TMR0IF = 0            ; Clear Timer0 overflow flag
    T0overflow = 0        ; Clear Timer0 overflow count
    TMR0 = 0              ; Clear Timer0 value

    Timer1 = $FFFF        ; Timer1 overflows on next cycle of 32768 Hz clock
    TMR1IF = 0            ; Clear Timer1 overflow flag
    TMR1ON = 1            ; Start Timer1 1 sec. period
    WHILE !TMR1IF : WEND  ; Synchronize to 32768 clock
    INPUT PSCLKOUT        ; Start counting freq input
    Timer1.15 = 1         ; Set Timer1 to 32768 for 1 Sec. period
    TMR1IF = 0            ; Clear Timer1 overflow flag

    WHILE !TMR1IF         ; while 1 sec. window is open  ---|
        IF TMR0IF THEN    ; count TMR0 overflows            | This section
            T0overflow = T0overflow + 1  ;                  | does the actual
            TMR0IF = 0                   ;                  | 1-Sec measurement
        ENDIF                            ;                  | Window
    WEND                                 ;               ---|
    LOW PSCLKOUT           ; Stop further counting
    T0value = TMR0         ; get Timer0 value

    PScount = 0            ; Clock out remaining prescaler
    WHILE TMR0 = T0value   ; until TMR0 value changes
        HIGH PSCLKOUT
        PAUSEUS 3
        LOW PSCLKOUT
        PAUSEUS 3
        PScount = PScount + 1
    WEND
    PScount = -PScount     ; negate to get prescaler count
RETURN

;----[Display frequency on LCD]-------------------------------------------------
DisplayFreq
    R2 = Result            ; Load Result into PBP's system vars for DIV32
    R0 = Result[1]
    FreqHigh = DIV32 1000  ; get left most 5 digits
    FreqLow = R2           ; remainder (R2) is right 3 digits

    LCDOUT $FE,$C0,"Freq = "
    IF FreqHigh > 0 THEN                        ; if any left digits
        LCDOUT DEC FreqHigh, DEC3 FreqLow,"   " ; display both left and right
    ELSE                                        ;  otherwise 
        LCDOUT DEC FreqLow,"     "              ; display only right digits
    ENDIF
RETURN

END

[dw_picbasic]

Thanks Darrel!!
I think I'll try to figure out how to mount the 32khz crystal onto the Labx-1 board.
I may be able to create a small pcb with headers that I can plug into the female header pins on the side of the 887a.

I should be able to see the 32khz oscillator with an Oscope to verify its running.
Interesting, I did play with loading different values into the high byte of Timer1s counting register and had it pull a pin high for the duration until timer1 rolled over and into the interrupt routine. 207 was what gave me a 1 sec pulse.
So I assumed it was the right number to load.

Thanks again for providing the code.
It will be super fun to try it out :-]
Duane

[dw_picbasic]

I had a question...but connected the dots when I posted it.

[dw_picbasic]

Hi Darrel,
I'm curious about something in the code
I see that you capture the Timer1 overflow count and load it into RESULTS.[bit16-31]
Then load the remaining count in TMR0 into RESULTS.[bit8-15]
But I thought that TMR0 is a 16 bit register....how is it we're loading its value into an 8 bit location in RESULTS?

Thanks!!
Duane :-]

[HenrikOlsson]

Hi Duane,
No, the TMR0 register is only 8 bits wide, that's why you need to use the trick with getting the remaining count out of the prescaler.
So, RESULT is a total of 4 bytes where the two most significant bytes are the number of TMR0 overflows, the next byte is the TMR0 count (where each count equals 256 transitions of the inputsignal due the 1:256 presacaler ratio) and the least significant byte is the number of transitions "stored" in the prescaler.

/Henrik.

[dw_picbasic]

Ah!
Thats right!!...sorry... I forgot the Timer0 is an 8 bit register.
I slipped on that one :-/

Thanks!