Making a timer, 32.768kHz+555+DT_INT. Good idea?

[Darrel Taylor]

The timer continues counting no matter what the program is doing.

And yes, it does take time to save all the PBP system registers before it gets to the interrupt handler.
But that has no affect on the reload value.

Your problem before was that you were overwriting the timers value with TMR1L = 0.

Here is the program I used with the Digital Clock Generator shown above, and it does keep perfect time.

;--------------------------------------------------------------
wsave        VAR BYTE $70 SYSTEM
INCLUDE "DT_INTS-14.bas"     ; Base Interrupt System
INCLUDE "ReEnterPBP.bas"     ; Include if using PBP interrupts

ASM
INT_LIST  macro    ; IntSource,    Label,  Type, ResetFlag?
        INT_Handler   TMR1_INT,   _Clock,   PBP,  yes
    endm
    INT_CREATE               ; Creates the interrupt processor
ENDASM

@   INT_ENABLE   TMR1_INT     ; enable external (INT) interrupts
;--------------------------------------------------------------
Sec          VAR BYTE
Minute       VAR BYTE
Hour         VAR BYTE
SecChanged   VAR BIT

;--------------------------------------------------------------
ADCON1 = 7
TMR1L = 0
TMR1H = $80
T1CON = %00001011
PAUSE 250
LCDOUT $FE,1

;--------------------------------------------------------------
Main:
    IF SecChanged THEN
        SecChanged = 0
        LCDOUT $FE,$80, DEC2 Hour,":",DEC2 Minute,":",DEC2 Sec 
    ENDIF
GOTO Main

;--------------------------------------------------------------
Clock:
    TMR1H.7 = 1
    Sec = Sec + 1
    SecChanged = 1
    IF Sec = 60 THEN Sec = 0 : Minute = Minute + 1
    IF Minute = 60 THEN Minute = 0 : Hour = Hour + 1
    IF Hour = 24 THEN Hour = 0
@ INT_RETURN

[financecatalyst]

Thank you very much Darrel. Surely learnt something new in this project.

So, even when variables are getting saved before entering ISR, only lower bit of timer one is getting incremented in that time. Previously I was resetting it again to '0', which I shouldn't do and let it increment to keep it in sync. BUT it does not reach to higher bit of timer1 in such short time, so we only put TMR1H.7=1, which keep everything simple and in sync.

That is why you also said that in my code it does not matter if that statement is in the beginning of the code or end, because the increment does not reach that higher value even after executing some statements in my ISR.

Got it now (Atleast I hope I have this concept cleared FOREVER)

[Darrel Taylor]

Excellent!

Now you really have "Got It".
And described it well.

Cheers,

[financecatalyst]

I made my circuit on my breadboard. It works kind of OK (INT are longer than 1 sec intervals) with TICON=%00001111 the clock still keeps incrementing even when I take out the 32KHz crystal from RC0-RC1.

The clock stops with
TICON=%00001011, seems Interrupts stop happening with this setting. Can someone please put some light on why this could be happening?

[financecatalyst]

Anyone? Should I start a new thread with this problem?

[mackrackit]

Maybe??
Do you have the Watchdog turned off?

[financecatalyst]

Maybe??
Do you have the Watchdog turned off?

Observations:
Watchdog is OFF.I just tried it with 4MHz oscillator, everything works fine. Intervals are 1 sec as expected. I took out the 32kHz crystal while PIC was working, it suddenly increased the speed of counting seconds(I WAS EXPECTING IT TO STOP ENTERING IN ISR) i.e. interrupts started happening a little faster. I inserted the crystal back in, the speed became ideal i.e. 1 sec interrupts.
Two questions now please:
1) Why didn't the Interrupts Stopped when I took the crystal out?
2) Why things get slow when I use 32768 Hz crystal as an oscillator for the PIC as well as the timer? 4MHz for PIC increases the current consumption to 2.5mA which is criminal when running on batteries.