12F675 / MCLR use

[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 ...)