Jump from ISR

[yasser hassani]

Hi anyone.
I am working on project and I've confronted with a problem. I want to jump from Interrupt service routine to subroutine and return from it and continue ISR.
In other words is it possible in PBP to call a subrotine when program is executing ISR. Thanks for your reply.

[mister_e]

Yes it's possible... case by case, just post your code here, tell us what you want to do, and we will be able to tell you better.

[yasser hassani]

Hi dear Mister_e
Thanks for your reply. Excuse me for delaying in my reply. I was too busy.
Suppose that we have this program:

'*****************************************************************
'*                         LCD Deifnes                           *
'*****************************************************************    
    
    DEFINE LCD_DREG PORTD               ' I/O port where LCD is connected
    DEFINE LCD_DBIT 4
    DEFINE LCD_RSREG PORTD
    DEFINE LCD_RSBIT 2                  ' Register select pin
    DEFINE LCD_EREG PORTD
    DEFINE LCD_EBIT 3                   ' Enable pin
    DEFINE LCD_BITS 4                   ' 4-bit data bus
    DEFINE LCD_LINES 2                  ' LCD has 2 character lines

	STATE 	var Byte
	I 	var Byte
	 	 
	PORTA = 0
	PORTB = 0
'************************************************* ****************
'* Interrupt Initialzing *
'************************************************* **************** 

    INTCON     = %10001000 ' GIE and RBIE are set
    OPTION_REG = %10000000

'************************************************* ****************
'* Initialzation *
'************************************************* ****************

    PORTB = 0
    TRISB = %00010000

    ON INTERRUPT GOTO DIRECTION

'************************************************* ****************
'* Main Program *
'************************************************* ****************

MAIN:

    lcdout $fe,1,"Main Routine"

    FOR I = 1 to 50 : PAUSE 10 : NEXT I ' For quick response
    GOTO MAIN
    END

'************************************************* ****************
'* Interrupt Service Routine *
'************************************************* ****************

    DISABLE

DIRECTION:

    STATE = PORTB	' End of Mismatch Condition

    lcdout $fe,1
    lcdout "Interrupt !!!"

    IF State.4 THEN

	   LCDOUT $FE,$C0," LOW to HIGH "
	
    ELSE

	   LCDOUT $FE,$C0, " HIGH to LOW "
	
    ENDIF
	
    PAUSE 100

    INTCON.0 = 0

    RESUME

    ENABLE

    END

When I want to move LCD display command out of ISR like below, the program doesn't work correctly!

'************************************************* ****************
'* Interrupt Service Routine *
'************************************************* ****************

    DISABLE

DIRECTION:

    STATE = PORTB	' End of Mismatch Condition

    lcdout $fe,1
    lcdout "Interrupt !!!"

    IF State.4 THEN

	   GOSUB L2H
	
    ELSE

	   GOSUB H2L
	
    ENDIF
	
    PAUSE 100

    INTCON.0 = 0

    RESUME

    ENABLE

    END

L2H:
    LCDOUT $FE,$C0," LOW to HIGH "
    RETURN
H2L:
    LCDOUT $FE,$C0," HIGH to LOW "
    RETURN

[Darrel Taylor]

Just like with the ISR itself, ... any subroutines jumped to from the ISR must be DISABLED from further interrupts, or they will attempt to interrupt themselves.

Moving the ENABLE line to after the H2L: subroutine should help.
<br>

[yasser hassani]

Thanks alot

[yasser hassani]

Thanks Dear Taylor
If you see the first program you'll find out infact your suggestion (Moving the ENABLE line to after the H2L: subroutine should help) is used at it. My problem is about second program.
Suppose that I want to implement this:
When H2L occures, the program should start displaying contents of EEPROM (We call Address). Address increments one by one till interrupt L2H occures. Now program should start displaying Address again but in this subroutine Address decrements one by one. How can I do that?
Please help me.
Thanks alot.

[Acetronics2]

Hi, Yasser

From reading your posts, I understand you want to scan your EEPROM, increasing address way, on a PORTB.4 H to L transition and decreasing addresses on a L to H transition ...

Ok ...

just use a FOR - NEXT EEPROM reading loop in the main program , if a "H2L" flag is set and a FOR-NEXT-STEP-1 EEPROM loop if a "L2H" flag is set.

Note I use 2 flags to let the initial "no transition" condition usable for something Else...

The ONLY questions will be : do you want to toggle reading order if EEPROM reading is not complete ???
What will you do when EEPROM reading is complete ??? ( seems you wait for further transition ... )

This has a strange smell of "K2000 scanner" or scrolling device ... really don't know why ... LOL !

Alain

[Darrel Taylor]

If you see the first program you'll find out infact your suggestion (Moving the ENABLE line to after the H2L: subroutine should help) is used at it. My problem is about second program.

The second program is the one I was talking about.
The subroutines are not DISABLE'd.
<br>