MCLR Question.

[muddy0409]

Thanks people.
Mel, the real part I need to know is what do the ports do, while in reset, ie do they turn off, or on, or no change? They will be off'ed at startup, but is a semi permanent reset equivelent to "startup"?, Intriguing, ain't it?
Where do I come up with these bloody questions??

[Acetronics2]

Hi Peter

At reset ( or power up ...) all ports are INPUTS ...but output flip flops do not have a specific reset value ...
that's why, it's better to write output values at start before defining inputs and outputs ...

read you soon ...
Alain

PS: hi, Mel
sometimes output values have to bet set to 1 at power up !!! ... with no "0 " transients allowed !!! Programmable curve Electronic ignition program available today ... which shows it ... don't say it's pure assembler to the list !!!

[Melanie]

Datasheet!

If you Power-On your PIC yet hold MCLR Low, your PIC will be in the Power-On start-up state until MCLR goes high. Port I/O's will be INDETERMINATE. They can be pulled High, or Low or be High-Impedance Input.

Only once you've set TRIS and assigned an initial I/O state, subsequently then when MCLR goes low, the I/O's will REMAIN in the state prior to MCLR stopping the show.

Let me reitterate in case you missed it, if you've never run your PIC following power-on (because MCLR is being held low), you CANNOT guarantee the state of the I/O's.

Read the Datasheet for your PIC.

[muddy0409]

Right, thanks heaps Mel.
Funny as it may seem that's just what I figured after reading, in more detail, about various chips. It's good to have someone who knows these things inside out to agree with me.
That comes from working with PICs all day, every day as I gather from your various posts.

Thanks again Mel, and Alain.
Your sort of comitment to this gear is what makes this a great forum for the old twits like me.