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Groups > linux.debian.user > #205700

Re: Swapping Drives - Sanity Check

From John Hasler <jhasler@newsguy.com>
Newsgroups linux.debian.user
Subject Re: Swapping Drives - Sanity Check
Date 2019-02-23 18:00 +0100
Message-ID <xuIOB-1Dr-1@gated-at.bofh.it> (permalink)
References <xuiU9-3dG-1@gated-at.bofh.it> <xuAo2-539-5@gated-at.bofh.it> <xuF4l-7NM-1@gated-at.bofh.it> <xuGMN-qS-3@gated-at.bofh.it>
Organization Dancing Horse Hill

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rhkramer writes:
> Hmm, that surprises me -- I guess I would have expected that you want
> the data pins connected first (while no power is applied), and
> disconnected last (again, while no power is applied).

Data pins can supply current.  They have to in order to charge and
discharge load and transmission line capacitance and drive load
resistance.  If you connect a data pin that has voltage on it to an
input of an integrated circuit that's part of an unpowered device
current will flow into the input, through the IC, and out the power pin
to the rest of the device.  This current may exceed the maximum that the
input can handle.

There has to be a return path, of course.  This could be the common,
another data pin, or, worst of all, chassis ground in which case you
will be subjecting both systems to whatever hum and/or ground loop
current is present.

All external connections to a device should incorporate protection, but
this not only adds cost: it slows data.
-- 
John Hasler 
jhasler@newsguy.com
Elmwood, WI USA

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Thread

Swapping Drives - Sanity Check "Stephen P. Molnar" <s.molnar@sbcglobal.net> - 2019-02-22 14:20 +0100
  Re: Swapping Drives - Sanity Check songbird <songbird@anthive.com> - 2019-02-22 15:20 +0100
    Re: Swapping Drives - Sanity Check David Christensen <dpchrist@holgerdanske.com> - 2019-02-23 09:00 +0100
      Re: Swapping Drives - Sanity Check songbird <songbird@anthive.com> - 2019-02-23 13:10 +0100
        Re: Swapping Drives - Sanity Check Michael Stone <mstone@debian.org> - 2019-02-23 17:20 +0100
          Re: Swapping Drives - Sanity Check Pascal Hambourg <pascal@plouf.fr.eu.org> - 2019-02-23 19:00 +0100
            Re: Swapping Drives - Sanity Check Michael Stone <mstone@debian.org> - 2019-02-23 20:20 +0100
              Re: Swapping Drives - Sanity Check Pascal Hambourg <pascal@plouf.fr.eu.org> - 2019-02-23 23:00 +0100
              Re: Swapping Drives - Sanity Check Felix Miata <mrmazda@earthlink.net> - 2019-02-23 23:40 +0100
                Re: Swapping Drives - Sanity Check Michael Stone <mstone@debian.org> - 2019-02-24 16:50 +0100
                Re: Swapping Drives - Sanity Check Felix Miata <mrmazda@earthlink.net> - 2019-02-24 18:40 +0100
      Re: Swapping Drives - Sanity Check Pascal Hambourg <pascal@plouf.fr.eu.org> - 2019-02-23 14:00 +0100
        Re: Swapping Drives - Sanity Check rhkramer@gmail.com - 2019-02-23 15:50 +0100
          Re: Swapping Drives - Sanity Check Pascal Hambourg <pascal@plouf.fr.eu.org> - 2019-02-23 17:00 +0100
            Re: Swapping Drives - Sanity Check rhkramer@gmail.com - 2019-02-23 17:30 +0100
              Re: Swapping Drives - Sanity Check <tomas@tuxteam.de> - 2019-02-23 18:10 +0100
                Re: Swapping Drives - Sanity Check mick crane <mick.crane@gmail.com> - 2019-02-23 22:00 +0100
                Re: Swapping Drives - Sanity Check <tomas@tuxteam.de> - 2019-02-23 22:10 +0100
              Re: Swapping Drives - Sanity Check Pascal Hambourg <pascal@plouf.fr.eu.org> - 2019-02-23 19:10 +0100
          Re: Swapping Drives - Sanity Check <tomas@tuxteam.de> - 2019-02-23 17:00 +0100
            Re: Swapping Drives - Sanity Check rhkramer@gmail.com - 2019-02-23 17:20 +0100
          Re: Swapping Drives - Sanity Check <tomas@tuxteam.de> - 2019-02-23 17:20 +0100
          Re: Swapping Drives - Sanity Check Michael Stone <mstone@debian.org> - 2019-02-23 17:20 +0100
          Re: Swapping Drives - Sanity Check John Hasler <jhasler@newsguy.com> - 2019-02-23 18:00 +0100
        Re: Swapping Drives - Sanity Check David Christensen <dpchrist@holgerdanske.com> - 2019-02-23 23:20 +0100
          Re: Swapping Drives - Sanity Check Pascal Hambourg <pascal@plouf.fr.eu.org> - 2019-02-23 23:40 +0100
  Re: Swapping Drives - Sanity Check Dan Ritter <dsr@randomstring.org> - 2019-02-22 15:20 +0100
    Re: Swapping Drives - Sanity Check "Stephen P. Molnar" <s.molnar@sbcglobal.net> - 2019-02-22 15:30 +0100
      Re: Swapping Drives - Sanity Check David Wright <deblis@lionunicorn.co.uk> - 2019-02-22 16:10 +0100
        Re: Swapping Drives - Sanity Check "Stephen P. Molnar" <s.molnar@sbcglobal.net> - 2019-02-22 17:40 +0100
          Re: Swapping Drives - Sanity Check Pascal Hambourg <pascal@plouf.fr.eu.org> - 2019-02-22 20:20 +0100
          Re: Swapping Drives - Sanity Check Michael Stone <mstone@debian.org> - 2019-02-22 20:30 +0100
            Re: Swapping Drives - Sanity Check David Wright <deblis@lionunicorn.co.uk> - 2019-02-23 03:00 +0100
              Re: Swapping Drives - Sanity Check Jimmy Johnson <field.engineer@gmail.com> - 2019-02-23 09:00 +0100
                Re: Swapping Drives - Sanity Check Pascal Hambourg <pascal@plouf.fr.eu.org> - 2019-02-23 09:40 +0100
          Re: Swapping Drives - Sanity Check Felix Miata <mrmazda@earthlink.net> - 2019-02-22 23:40 +0100

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