GPS Project: PIC18F26K22 or PIC18F46K22

[richard]

I guess we cant leave unassigned the bits

there is no such state , pins are either inputs or outputs or analog inputs , outputs can only be high or low
if you have no reason to use a pin as an output then leave as an input , if you have no reason to use a pin as a digital input you can leave it analog
the pic chip won't care. the pic chip does not care if outputs are high or low its only what they connect to that cares , it up to you to initialise the pins
in use to the correct type/state and direction to match the requirement of what they connect to and then make sure they stay that way.

[astanapane]

there is no such state , pins are either inputs or outputs or analog inputs , outputs can only be high or low
if you have no reason to use a pin as an output then leave as an input , if you have no reason to use a pin as a digital input you can leave it analog
the pic chip won't care. the pic chip does not care if outputs are high or low its only what they connect to that cares , it up to you to initialise the pins
in use to the correct type/state and direction to match the requirement of what they connect to and then make sure they stay that way.

now it is clear. Really appreciate your help.

Thanks a lot Richard.

[Ioannis]

I have my doubts on leaving inputs floating.

Usually if I have any unused ports, I turn them as outputs and clear them.

If they are inputs, maybe enable the pull ups if any or tie them to ground.

A floating pin can cause troubles in certain cases.

Ioannis

[richard]

if your program is adversely affected by an unused pin then your code is incomplete and needs more debugging

[Ioannis]

No the program itself but on the total current consumption as the CMOS do not like to be float.

Ioannis

[Dave]

Especially when in the presence of stray RF. They make rather nice antenna's.

[astanapane]

Especially when in the presence of stray RF. They make rather nice antenna's.

Ok then what is the most professional way in most of the cases to configure the pins?

Should we make all the non used pins as an outputs - low stage?

[richard]

its my understanding that pins left as inputs and tied or pulled down to vss will minimise current consumption.
when i'm breadboarding a design I let them float and have never had an issue , if you accidently plug something
into a input pin at least smoke is not released.