What is on GP4? Maybe you can connect GP5 to GP4 instead of VDD?

/Ruben

> =

> Hello,
> =

> I got a project ready to go into serial production and now my customer
> stepped up with an additional idea. He likes to have different features w=
ith 2
> differerent models, but hardware unchanged. It would be possible to load
> differerent software by ICSP, but I had another idea this morning:
> =

> I'm using a 12F519 with an unused RB5 pin. The circuit is powered all the
> time by 3V and just exits sleep mode when active. Now my idea is to use a
> "universal software" for both models and simply check the state of RB5 to
> decide which part of software to run. I don't like to solder tiny wires f=
rom RB5
> to Vss or Vdd respectively, so I thought of the following:
> =

> RB5 is located near Vdd, so I simply make a short between Vdd and RB5 if I
> like to have model 2 (or leave everything as is for model 1). =

> When starting up the circuit the first time or when batteries are changed
> the software looks for the state of RB5. To do this, I output a log.0 to =
RB5 and
> read the state immediately. If there is no connection to Vdd it should re=
ad zero
> again. But if there is a connection it should read log.1.
> =

> I tried this this morning and in fact it works so far, but my concerns ar=
e:
> =

> 1. I'm relying on the fact, that the capacity of the PIC's internal output
> circuitry is big enough to be stable until my read port function is done.
> 2. I'm stressing my RB5 port by outputting log.0 to a pin connected to Vd=
d. How
> often can I do this? Are there any experiences doing this?
> =

> I know, this is a strange idea, but on the other hand it might be a tricky
> way with nothing but a soldering point.
> =

> Any comments welcome!
> =

> Best regards
> =

> Peter
> =

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=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
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Ruben J=F6nsson
AB Liros Electronic
Box 9124, 200 39 Malm=F6, Sweden
TEL INT +46 40142078
FAX INT +46 40947388
ruben@pp.sbbs.se
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