Re: Single ended termination?.

--0000000000004e7ed805bae0dd57
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: quoted-printable

Hello,

The purpose of the terminator is to get the end of the transmission line
look like an infinitely long line with impedance equal to the line
impedance (120ohm with CAN) and thus prevent reflections. Thus, single
terminator may be installed into one end, but the another end remains
unterminated (infinite impedance), which leads into over- and undershoots.
While the communication will pass through, the transmission line is still
broken. From practical point of view, the most significant risk is that any
other problem more will lead into total black-out. And one shall keep in
mind that the physical layer design has a direct effect on the bit error
probability, which is a basis for residual error rate, which has further
effect on the availability and safety performance of the entire system --
it is easy to violate the system requirements with a poor CAN cabling
design.

There are some reference designs (published by Daimler) in the literature
for centre termination but they cannot be recommended, because each of such
networks needs to be intentionally fine tuned. In addition to the clumsy
design, such will be a service nightmare.

My recommendation is to adopt a standard cabling and connector scheme,
where you'll find batch cables, Y- or V-branches and termination plugs,
e.g. MiniChange, M12 or Deutsch DT04/06 series.

Best regards,

Heikki Saha, CTO
  M.Sc. Automation
  Dr.Tech. Electronics
TK Engineering Oy
Hovioikeudenpuistikko 13 as 3, 65100 Vaasa
+358 (0)50 588 6894
email: [email protected]
skype: heikki.saha_tke

We are also in the 17th iCC: https://www.can-cia.org/icc


On Tue, Feb 9, 2021 at 12:24 AM Al Thomason <[email protected]> wrote:

> I have a question for the group:  Every one of us has (and likely does)
> run with a single 120 ohm terminator on the development bench; and all
> references I know of in no uncertain terms disavow that practice for actu=
al
> end user deployment.   But I am asking if:   Does anyone know of a
> creditable study / reference talking to use the use of a single 120 ohm
> terminator in customer (production) deployments there the =E2=80=98CAN Wi=
ring=E2=80=99 is
> very local and Tx rates modest.
>
>
>
> Example, 250Kbps, 2-3 nodes over a total CAN distance of maybe 1-2m at ma=
x?
>
>
>
> Thank you,
>
>
>
> -al-
>
>
>
>
>

--0000000000004e7ed805bae0dd57
Content-Type: text/html; charset=UTF-8
Content-Transfer-Encoding: quoted-printable

<div dir=3D"ltr">Hello,<div><br></div><div>The purpose of the terminator is=
 to get the end of the transmission line look like an infinitely long line =
with impedance equal to the line impedance=C2=A0(120ohm with CAN) and thus =
prevent reflections. Thus, single terminator may be installed into one end,=
 but the another end remains unterminated (infinite impedance), which leads=
 into over- and undershoots. While the communication will pass through, the=
 transmission line is still broken. From practical point of view, the most =
significant risk is that any other problem more will lead into total black-=
out. And one shall keep in mind that the physical layer design has a direct=
 effect on the bit error probability, which is a basis for residual error r=
ate, which has further effect on the availability and safety performance of=
 the entire system -- it is easy to violate the system requirements with a =
poor=C2=A0CAN cabling design.</div><div><br></div><div>There are some refer=
ence designs (published by Daimler) in the literature for centre terminatio=
n but they cannot be recommended, because each of such networks needs to be=
 intentionally fine tuned. In addition to the clumsy design, such will be a=
 service nightmare.</div><div><br></div><div>My recommendation is to adopt =
a standard cabling and connector scheme, where you&#39;ll find batch cables=
, Y- or V-branches and termination plugs, e.g. MiniChange, M12 or Deutsch D=
T04/06 series.</div><div><br></div><div>Best regards,</div><div><br clear=
=3D"all"><div><div dir=3D"ltr" class=3D"gmail_signature" data-smartmail=3D"=
gmail_signature"><div dir=3D"ltr"><div><div dir=3D"ltr"><div><div dir=3D"lt=
r"><div><div dir=3D"ltr"><div><div dir=3D"ltr">Heikki Saha, CTO<br>
=C2=A0 M.Sc. Automation<br>
=C2=A0 Dr.Tech. Electronics<br>
TK Engineering Oy<br><font face=3D"arial, helvetica, sans-serif">Hovioikeud=
enpuistikko 13 <span style=3D"color:rgb(51,51,51);font-style:normal;font-we=
ight:400;letter-spacing:normal;text-align:start;text-indent:0px;text-transf=
orm:none;white-space:normal;word-spacing:0px;background-color:rgb(255,255,2=
55);float:none;display:inline">as 3</span><span style=3D"color:rgb(51,51,51=
);font-style:normal;font-weight:400;letter-spacing:normal;text-align:start;=
text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;bac=
kground-color:rgb(255,255,255);float:none;display:inline">, 65100 Vaasa</sp=
an></font><br>
+358 (0)50 588 6894<br>
email: <a href=3D"mailto:[email protected]" target=3D"_blank">heikki.saha@=
tke.fi</a><br>
skype: heikki.saha_tke</div><div dir=3D"ltr"><br><div>We are also in the 17=
th iCC: <a href=3D"https://www.can-cia.org/icc" target=3D"_blank">https://w=
ww.can-cia.org/icc</a><br></div></div></div></div></div></div></div></div><=
/div></div></div></div><br></div></div><br><div class=3D"gmail_quote"><div =
dir=3D"ltr" class=3D"gmail_attr">On Tue, Feb 9, 2021 at 12:24 AM Al Thomaso=
n &lt;<a href=3D"mailto:[email protected]">[email protected]</a>&gt=
; wrote:<br></div><blockquote class=3D"gmail_quote" style=3D"margin:0px 0px=
 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div la=
ng=3D"EN-US"><div class=3D"gmail-m_-2383135199217008694WordSection1"><p cla=
ss=3D"MsoNormal">I have a question for the group:=C2=A0 Every one of us has=
 (and likely does) run with a single 120 ohm terminator on the development =
bench; and all references I know of in no uncertain terms disavow that prac=
tice for actual end user deployment.=C2=A0=C2=A0 But I am asking if:=C2=A0=
=C2=A0 Does anyone know of a creditable study / reference talking to use th=
e use of a single 120 ohm terminator in customer (production) deployments t=
here the =E2=80=98CAN Wiring=E2=80=99 is very local and Tx rates modest.=C2=
=A0=C2=A0 <u></u><u></u></p><p class=3D"MsoNormal"><u></u>=C2=A0<u></u></p>=
<p class=3D"MsoNormal">Example, 250Kbps, 2-3 nodes over a total CAN distanc=
e of maybe 1-2m at max?<u></u><u></u></p><p class=3D"MsoNormal"><u></u>=C2=
=A0<u></u></p><p class=3D"MsoNormal">Thank you,<u></u><u></u></p><p class=
=3D"MsoNormal"><u></u>=C2=A0<u></u></p><p class=3D"MsoNormal">-al-<u></u><u=
></u></p><p class=3D"MsoNormal"><u></u>=C2=A0<u></u></p><p class=3D"MsoNorm=
al"><u></u>=C2=A0<u></u></p></div></div></blockquote></div>

--0000000000004e7ed805bae0dd57--

--
Subscribe, unscribe, and archives at www.canlist.org - report any problems to <[email protected]>