12F675 / MCLR use

[Acetronics2]

Hi,

Who could explain me that ???

This simple program is a flip-flop with button debouncing ... simple, eh !

( Button1 is on the low side - LOW level if pushed )

When using MCLR ... output ( GPIO.2) is LOW at power-up ... Ok

When disabling MCLR ( internal reset ) ... output is HIGH at power-up ... ???
Instead to what it should be !!!

Did I miss something ???

' Madproject
'
'Anti rebond pour sauter à la perche ( ??? )
'
' 16F629 mode INTOSC @ 4 Mhz
'
' le 03/09/2009 139 Lignes
'******************************************************************************
'******************************************************************************

'******************************************************************************
' CONFIG
'******************************************************************************

 @    __CONFIG _INTRC_OSC_NOCLKOUT & _WDT_ON & _PWRTE_ON & _MCLRE_ON & _CP_OFF & _BODEN_ON
 
DEFINE OSC 4
DEFINE OSCCAL_1K 1
DEFINE BUTTON_PAUSE 100

ADCON0		= 0
ANSEL		= 0
CMCON		= 7
VRCON 		= 0
OPTION_REG.5 = 0
OPTION_REG.7 = 1   	'Disable Pull-Ups



                                              
Bouton1     VAR GPIO.0
Bouton2     VAR GPIO.1
Sortie      VAR GPIO.2
'LedVisu     VAR GPIO.3			' Attention : Sortie PIC en C/O !!!
LedVisu		 VAR GPIO.4
'set         VAR GPIO.5

x           VAR byte
Delay		VAR byte

GPIO 		= %00000011			'All pins LOW IF outputted - no startup bug.
TRISIO 		= %00000011         'set GPIO.0 & GPIO.1 as inputs Others Output

'******************************************************************************
Attente: ' On attend !!!
'******************************************************************************

    Delay = 0
   	BUTTON Bouton1,0,255,0,Delay,1,Action		' Poussoir à la masse enfoncé

	PAUSE 10									' 10 ms entre scans
	GOTO Attente   								' Non? : retour départ 
 
'******************************************************************************   
Action:	' On a enfoncé le bouton plus de 100 ms
'******************************************************************************

   TOGGLE Sortie								' On inverse la sortie
   TOGGLE LedVisu
   
'******************************************************************************   
Attente2: ' On attend que le bouton soit relâché ...
'******************************************************************************

   Delay = 0
   BUTTON Bouton1,1,255,0,Delay,1,Attente		' Le bouton est il relaché ???
   												'
   GOTO Attente2									'  NON On boucle

'******************************************************************************   
   END

Alain

[Melanie]

Never trust the state of any I/O on Power-Up - regardless of what the Datasheet says.

Always preset your I/O's within your program to what you want them to be as one of the first things you do when initialising the PIC.

[dhouston]

From the datasheet...

Figure 3-3 shows the diagram for this pin. The GP3 pin
is configurable to function as one of the following:
• a general purpose input
• as Master Clear Reset

and...

bit 5 MCLRE: GP3/MCLR pin function select(5)
1 = GP3/MCLR pin function is MCLR
0 = GP3/MCLR pin function is digital I/O, MCLR internally tied to VDD

and from your config fuses...

_MCLRE_ON

[Melanie]

I think Alain is talking about GPIO.2 having an anomally when you configure GPIO.3 (MCLR) for different states. In theory it shouldn't effect that pin...

[dhouston]

I think Alain is talking about GPIO.2 having an anomally when you configure GPIO.3 (MCLR) for different states. In theory it shouldn't effect that pin...

Ahhh! I misunderstood and thought he was trying to make GPIO.3 an output although I expected he would know better. I should have known better.

What happens if the order of the TRISIO = and GPIO = statements are reversed?

[Acetronics2]

Never trust the state of any I/O on Power-Up - regardless of what the Datasheet says.

Always preset your I/O's within your program to what you want them to be as one of the first things you do when initialising the PIC.

Hi, Mel

You do know the only one I trust in, is you, Mel ... ( Violins [ON] , Crooner [ON], Rose Petals drop [ON], Champagne [ON] ... )

I just think you missed my two I/O Config lines ... ( Was late, eh ...)

I must tell it ALSO affects GPIO.4 ... so, I have to try adding a little PAUSE after those CONFIG Lines, I smell a Power on little issue ... That make BUTTON read a low level when power up ...

OR May be a " HIGH GPIO.0 " Command before the first BUTTON Command to ensure the High Level ...

Testing a HIGH level for Button1 pressed is to also an idea ( some capacitive effects on GPIO.0 ??? ... despite it has no load but a Pullup resistor !) ...

But, that's not something " normal " ...

Alain

[Acetronics2]

As I smelled ...

Adding a little PAUSE 50 ( 40 is not enough ! ) just past the I/O config Lines solved the issue ...

HIGH GPIO.0 didn't work ...

Alain ( bug killer ...)