Re: [CAD_CAM_EDM_DRO] Re: Parallel Port Interface cards

I agree . I recently has a few customers that switched from ECP to EPP and
the step and direction problems went away.
Dan Mauch
low cost stepper and servo motors.
cases for Gecko drives
kits and assembled 3-4 axis drives
www.camtronics-cnc.com
www.seanet.com/~dmauch

----- Original Message -----
From: "Jon Elson" <elson@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Wednesday, January 10, 2007 9:42 AM
Subject: Re: [CAD_CAM_EDM_DRO] Re: Parallel Port Interface cards


> Phil Mattison wrote:
>
>>You raise a fairly perplexing issue. Since the PC parallel port uses
>>open-collector drivers for outputs and does not have built-in pullup
>>resistors on inputs or outputs,
>>
> I don't believe this is true. Maybe it depends on what BIOS mode
> selection
> (AT, PS/2, EPP, etc.) has been made, but when I use any recent mobo
> parport
> in EPP mode, it definitely has active pull-up, ie a transistor, when
> driving the
> data lines as output.
>
> I have also found that all input control signals have either pull-up or
> pull-down
> on them. It varies from maker to maker exactly what the value of these
> pull-up/
> pull-downs is, but they all seem to have this and go to a defined
> default state
> when nothing is connected.
>
> I sell 3 devices that control motion systems using the parallel port,
> all in EPP mode,
> and so I have spent DAYS looking at parallel port signals on an
> oscilloscope.
>
> Jon
>
>
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