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pleaze any one can answer me what is the difference between... — Parallax Forums

pleaze any one can answer me what is the difference between...

ArchiverArchiver Posts: 46,084
edited 2003-07-08 14:06 in General Discussion
In a message dated 7/3/2003 11:40:29 PM Pacific Daylight Time,
rme90@y... writes:

> plz tell me the difference between pin 4(Vss)and pin 23 (Vss)?
>
>
> thx for helping...........Romero

Romero,

The two pins are the same.


[noparse][[/noparse]Non-text portions of this message have been removed]

Comments

  • ArchiverArchiver Posts: 46,084
    edited 2003-07-05 04:26
    --- In basicstamps@yahoogroups.com, smartdim@a... wrote:
    > In a message dated 7/3/2003 11:40:29 PM Pacific Daylight Time,
    > rme90@y... writes:
    >
    > > plz tell me the difference between pin 4(Vss)and pin 23 (Vss)?
    > >
    > >
    > > thx for helping...........Romero
    >
    > Romero,
    >
    > The two pins are the same.


    Well, they are different numbers and on different sides of the chip
    so there is some great schematic and layout differences, so although
    electronically they are the same, physically, they are different.

    and if you have ever had to run a trace over the mountain and thru
    the woods, you do appreaciate the difference.

    Dave



    >
    >
    > [noparse][[/noparse]Non-text portions of this message have been removed]
  • ArchiverArchiver Posts: 46,084
    edited 2003-07-05 05:09
    Yah, they're linked to the same silicone inside, just one's conveniently
    placed for connection to a serial port, and the other's with the power
    circuitry. No technical difference, just placed for convenience I guess...

    - Robert


    Original Message
    From: <smartdim@a...>
    To: <basicstamps@yahoogroups.com>
    Sent: Friday, July 04, 2003 9:23 AM
    Subject: Re: [noparse][[/noparse]basicstamps] pleaze any one can answer me what is the
    difference between...


    > In a message dated 7/3/2003 11:40:29 PM Pacific Daylight Time,
    > rme90@y... writes:
    >
    > > plz tell me the difference between pin 4(Vss)and pin 23 (Vss)?
    > >
    > >
    > > thx for helping...........Romero
    >
    > Romero,
    >
    > The two pins are the same.
    >
    >
    > [noparse][[/noparse]Non-text portions of this message have been removed]
    >
    >
    > To UNSUBSCRIBE, just send mail to:
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    Body of the message will be ignored.
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    >
  • ArchiverArchiver Posts: 46,084
    edited 2003-07-06 13:38
    Another reason you want more than one ground
    is to reduce the amount of noise on the
    ground lines.

    Digital logic has high-frequency switching
    transients. If you have a long single ground
    wire, it looks like a (small) inductance.

    (An inductor is like a small coil. It maintains
    a magnetic field while current is flowing.
    When the circuit is broken, the collapse
    of the magnetic field makes current continue
    to flow. Thus inductance slows the
    instantaneous change of current.)

    (Even if the 'inductor' is a long straight
    wire, there is a little of this magnetic
    effect.)

    When you have a switching transient, a lot
    of current is needed for a very short time.

    The inductance of the wire means that there
    is a ramp-up time for the current to get to
    the chip. While this ramp-up is occurring,
    the voltage at the chip drops -- thus giving
    you a downwards voltage spike, (called
    ground bounce) which in turn
    affects how fast the chip can switch.

    One way to prevent this is to have multiple
    connections to ground. This reduces the
    effective length of the ground wire, and
    thus reduces the inductance of the connection
    to ground.

    This also allows 'high-current'
    devices to have a different path to ground
    than lower current devices, which reduces
    the amount of ground-bounce noise coupled
    between devices.

    --- In basicstamps@yahoogroups.com, "Dave Mucha" <davemucha@j...>
    wrote:
    > --- In basicstamps@yahoogroups.com, smartdim@a... wrote:
    > > In a message dated 7/3/2003 11:40:29 PM Pacific Daylight Time,
    > > rme90@y... writes:
    > >
    > > > plz tell me the difference between pin 4(Vss)and pin 23 (Vss)?
    > > >
    > > >
    > > > thx for helping...........Romero
    > >
    > > Romero,
    > >
    > > The two pins are the same.
    >
    >
    > Well, they are different numbers and on different sides of the chip
    > so there is some great schematic and layout differences, so
    although
    > electronically they are the same, physically, they are different.
    >
    > and if you have ever had to run a trace over the mountain and thru
    > the woods, you do appreaciate the difference.
    >
    > Dave
    >
    >
    >
    > >
    > >
    > > [noparse][[/noparse]Non-text portions of this message have been removed]
  • ArchiverArchiver Posts: 46,084
    edited 2003-07-08 14:06
    Yes, but only on the "enhanced" chip :^) (I think you meant "silicon")

    (no "language lawyer" flames, please...It just struck me as funny at the
    time...)

    >Message: 15
    > Date: Fri, 4 Jul 2003 22:09:18 -0600
    > From: "Robert Ussery" <uavscience@f...>
    >Subject: Re: pleaze any one can answer me what is the difference
    between...
    >
    >Yah, they're linked to the same silicone inside, just one's conveniently
    >placed for connection to a serial port, and the other's with the power
    >circuitry. No technical difference, just placed for convenience I guess...
    >
    >- Robert



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