On Fri, 3 Aug 2001 18:01:56 +0200, wouter van ooijen & floortje hanneman
<wf@XS4ALL.NL> said:

> > There's the first 10.  Anybody else got additions?
>
> ad 3: The fact that leaving RB3 floating does no harm on some chips (when
> the moon is right) should not be taken as proof that holding the pin low
is
> not needed in geneal. And note that 16f62x's uses RB4 as LVP enable.
>
> - At power-up the F87x's default to analog inputs for some port a pins.
You
> must disable the analog function to use these pins as discrete (digital)
> input. Might be the case for other types too?
>
> - beware of SUBLW and SUBWF. Contrary to what you could expect from an
> accumulator-architecture these instructions substract W from something,
not
> something from W. The SUBLW (Substract Literfal from W) menemonic reflects
> this, the SUBWF mnemonic was especially choosen to confuse you.
>
> - beware of SUBLW and SUBWF. Take a good look at the instruction
description
> to see how the carry is set, it might not agree with what you expect!
>
> - The OPTION instruction can - on the chips that support it! - be used
> without any problem. Microchip is not suddenly gona drop this instruction
> from an existing chip. The comment in the manuals should be understood as
> stating that it might wel be dropped from FUTURE 14-bit core chips. So if
> you want to have maximum code portability avoid OPTION, otherwise just use
> it.
>
> - When you have programmed your first PIC with with a blinking LED and it
> blinks at a rate that you did not expect and no matter what you change the
> blinking stays at that rate check whether you have disabled the watchdog.
>
> - When you have programmed your first PIC with with a blinking LED no
matter
> what you change the LED stays on you might well be blinking the LED at a
> very high rate. To check: connect it the other way round (to VCC instead
of
> GND or vice versa).
>
> - The best way to kill a PIC is to connect the VCC/GND backwards. When
this
> is not your aim you might consider putting the PIC in a (round pin) socket
> and solder an anti-parallel diode across the GND/VCC pins. Make sure that
> the combo can still be put in a (flat pin) socket. This arrangement also
> protects you against broken PIC pins.
That's unusual. I've never killed a PIC by putting it in backwards. I did
kill a #5 power supply doing that though. The PSU whistled to tell me the
current limit had been exceeded then promptly died. Now I'm using a 4.5V
regulated PSU (that outputs 4.8V) to run my projects. Thanks for the tip,
Wouter.
I have fitted my only PIC16F84-10/P in a high-quality turned-pin socket
though. Tinned beryllium copper contacts (according to my supplier).

> - When your program worked OK in a windowed chip but fails in an OTP (or
the
> other way round), or your windowed chips fails in bright light (or in
total
> darkness, or the other way round)  you might have uninitialized variables.
> Cover the windowed chip with something  REALLY black (not just UV-black)
and
> it should behave like an OTP. The metallic-like things used to make 5.25
> inch floppies write-protected are reported to work quite well.
They work well on EPROMs too. Get the metallized ones - paper labels worketh
not a toss.

--
Phil.
philpem@bigfoot.com
http://www.philpem.f9.co.uk/

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