ASM code

[Bill Legge]

Help please.

The PIC is an 18F8772 on a Futulec board (so hopefully the wiring is correct).
I'm trying to use assembler to make the MCU produce two pulse streams for a set number of pulses:

1. I use TIMER0 and TIMER1 for the inter-pulse delays.
2. A simple 'count down' for the pulse duration.
3. A counter that holds the numer of pulses to be generated, this is decremented - and when the counter hits zero - the routine should end.

The code works OK - BUT! keeps 're-running.' i.e it puts out the required number of pulses, pauses for a bit and then does it all over again.

Debugging with an ICD2 shows all the SFRs changing properly and the code ending after the requisite number of pulses - but when running normally it just keeps looping.

The last few lines of ASM code is

Main_loop:                   ; Check if X_steps_lb is zero			tstfsz	X_steps_lb   ; Test, skip next if equal
	goto	Main_loop    ; More steps to do, so loop	
	bcf	INTCON,7    ; Disable all high priority interrupts
	bcf	INTCON,6    ; Disable all low priority interrupts
	bcf	T0CON,7	    ; Timer0 off
	bcf	T1CON,0     ; Timer1 off	
	end

I've not posted all the code because I don't think anyone would trawl through it.

The CONFIG settings are:

                                           ;  Configuration bits
             CONFIG  OSC = HSPLL         ; Run at 4X speed
             CONFIG  CP0=OFF              ; Disable code protect		
             CONFIG  PWRT = OFF         ; Powerup off so DEBUG works            
             CONFIG  WDT=OFF             ; WDT off
             CONFIG  LVP = OFF            ; LVP off
             CONFIG  WAIT = OFF          ; External bus data wait disabled

The re-set on MLCR is OK. The IDE is MPLAB. Anyone got any ideas?

Regards Bill Legge

[mackrackit]

Main_loop:                   ; Check if X_steps_lb is zero			tstfsz	X_steps_lb   ; Test, skip next if equal
	goto	Main_loop    ; More steps to do, so loop	
	bcf	INTCON,7    ; Disable all high priority interrupts
	bcf	INTCON,6    ; Disable all low priority interrupts
	bcf	T0CON,7	    ; Timer0 off
	bcf	T1CON,0     ; Timer1 off	
END_LOOP:
       GOTO END_LOOP
	end

Once it hits END_LOOP it will stay there forever, This is sorta what PBP's END does.. I think//

[Bill Legge]

Dave,

Thanks - I've just tried that and it works fine - the first time in 2 days that I have managed to get the code to output the correct number of pulses.

However, I presume that when I incorporate the .asm code inside PBP the loop will prevent the .asm from ever finishing?

ASM
; lots of my asm code goes here
End_loop:
goto End_loop
ENDASM

Any other ideas please? What on earth is making the PIC ignore all the 'end stuff' instructions?

Regards Bill Legge

[mackrackit]

ASM
; lots of my asm code goes here
ENDASM

END ' THE PBP TYPE

When you jump out of the ASM routine and go back to PBP the END command should do what you want.

[Bill Legge]

Dave,

Thanks for your support and interest.

Having got it to work using the 'end-loop' process you suggested, I had a further play-around with the interrupts - and made it work!

I added the code:

bcf  RCON,7    ; Clear IPEN=0, disable priority interrupts

And now all is OK.

If anyone is interested in the code I'm happy to put it up here. The routine uses ASM to:

1. Drive 2 stepper motors at the same time.
2. Main purpose is to get diagonal moves on an XY plotter
3. The asm code is passed parameters by PBP:
a. X steps to be done
b. Y steps to be done
c. X inter-pulse delay
d. Y inter-pulse delay
4. Code has yet to be 'polished' and oly works with byte size parameters.
Next is changing to accept WORD size parameters.

Once again - thanks for your help.

Regards Bill Legge

[Archangel]

bcf  RCON,7    ; Clear IPEN=0, disable priority interrupts

If anyone is interested in the code I'm happy to put it up here. The routine uses ASM to:

1. Drive 2 stepper motors at the same time.
2. Main purpose is to get diagonal moves on an XY plotter
3. The asm code is passed parameters by PBP:
a. X steps to be done
b. Y steps to be done
c. X inter-pulse delay
d. Y inter-pulse delay
4. Code has yet to be 'polished' and only works with byte size parameters.
Next is changing to accept WORD size parameters.

Hi Bill,
I would like to see it,
Thank You.
JS

[Darrel Taylor]

I added the code:

bcf  RCON,7    ; Clear IPEN=0, disable priority interrupts

And now all is OK.

I have my doubts about that.

IPEN defaults to 0 on Power-Up/Reset.
So unless you have another RCON statement in your program that already changed it to 1, that statement will have no effect.
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