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SV: [Lcdproc] HD44780 problems


Chronological Thread 
  • From: Luis.F.Correia AT seg-social.pt (Luis.F.Correia)
  • Subject: SV: [Lcdproc] HD44780 problems
  • Date: Fri Aug 29 07:41:01 2003

> On Thu, 28 Aug 2003 18:47:31 -0400, Guillaume Filion wrote:
>
> > Just to make sure not to confuse anyone, a pull-up is a resistor
> > between a line and a VCC (5V for TTL). A pull-down is a resistor
> > between a line and a ground (0V). If I remember correctly, your
> > solution was a pull-up.
>
> Most likely. Most (all?) TTL based outputs are open
> collector, so with
> the driver transistor off ( to give logic 1, +5v, on the line) the
> output line floats unless pulled up by a resistor.
>

Most new paralell ports have weak pull-ups, which may not be enough
to guarantee stability of the LCD, specially if long cables are used.
(long=2meters)




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