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'[pic]: setting option reg'
2003\02\02@081657 by rad0

picon face
correct me any where wrong please,
but,
if you set option reg = %10100000, bit 7 and 5

bit 7, turns off(set) or on the port B pull ups...(pull up internal
resistors--correct?)
-- is there any reason to do this if you are not going to use portB??

bit 5, TMR0 clock source select bit
--any need to set this bit if you are not using TMR0 ??
by setting this, are you removing 'the internal cycle clock' SO therefore,
removing unwanted effects?
(I don't quite understand the timers in general, but I really want to know
if
you need to set this, if you're not using it.  and perhaps some info on
what this thing is, would help too.)

If you are not using port A or B, do you need to set bit 7 and/or bit 5


thanks for any help

while I'm at it, setting adcon0 = 00000000 -- does this just turn off
the A/D altogether, and again, do you need to do this, if you're not
using the A/D---is this the last step, after setting up adcon1 as you
wish, to conserving the power used by the A/D system?

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2003\02\02@125732 by Olin Lathrop

face picon face
> bit 7, turns off(set) or on the port B pull ups...(pull up internal
> resistors--correct?)
> -- is there any reason to do this if you are not going to use portB??

No, Microchip just threw it in there so see if you'd notice.  You get a
gold star now and can go back to playing with the 'puter.

Of course there's a reason!  They wouldn't spend transistors on it
otherwise.  Passive pullups are sometimes useful.  One example is that it
allows connecting to a switch with no additional parts.  Put the switch
between the port B pin and ground and enable passive pullups.  The bit
will read 1 when the switch is open, 0 when closed.  The passive pullups
are designed so that shorting them to ground causes no harm and doesn't
draw lots of current (although you wouldn't want to do this for long
periods in low power applications).


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