Re: Embedded Ethernet

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Well if you can switch cores, there's:

http://www.microcontroller.com/news/dallas_8051_ethernet.asp

Or if not, why didn't you like:

http://www.smsc.com/main/catalog/lan91c111.html

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Re: Embedded Ethernet
Since the ATMega128 can't handle100mbps (ISA bus is too slow) isn't the
issue is moot?

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one
something



Re: Embedded Ethernet

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[top post fixed]

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Line rate and the CPU/bus's ability to handle this speed are not
intertwined. If the 100Mbit controller can buffer a full frame at 100Mbs
then it gives the CPU the ability to accept 100Mbs frames. Whether the CPU
and bus can keep up with large amounts of these frames is another issue. I
suspect that this design requires high line rate speed but not high data
rates. Kind of like running a serial at 115kBaud but only sending a couple
of characters per "long" unit of time.

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Re: Embedded Ethernet

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[...]

I would dare say they are, at least as far as dedicated point-to-point
lines are considered.  Having a high-speed capable line sit unused for
the majority of the time is bound to be wasting some (costly) resource
somewhere.

Shared-medium networks would be a different issue, obviously, but I
don't quite see what could be the benefit of having that buffer to
hold one complete Ethernet frame's worth of data on the embedded
device's end of that line, instead of at the hub, switch or whatever
is on the other end, where it'd usually be quite a bit easier to
accomodate it.

The only thing that would really be improved by such a plan would be
the latency, not the bandwidth.  Sending shorter packets might be a
better plan, in that case.

--
Hans-Bernhard Broeker ( snipped-for-privacy@physik.rwth-aachen.de)
Even if all the snow were burnt, ashes would remain.

Re: Embedded Ethernet
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And how exactly will a point to point environment be improved by
changing the ethernet from 100 Mbps to 10 Mbps?  What costly resource
does 100 Mbps Ethernet have that a 10 Mbps Ethernet does not have?  


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Yes, I can see that you don't understand.  If you do all the math, you
will find that data going to the embedded target can travel at the full
rate and reach the target in less time.  So the target can start working
on the data sooner.  Likewise data being sent by the embedded target
will take less time if it travels at the higher rate freeing up the
buffer more quickly.  


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Shorter packets may make some number smaller that is reported by
software and you are equating with latency.  But the real latency does
not change, and in fact may get worse.  No one cares how quickly a part
of a buffer is sent.  If the entire buffer needs to be sent before
processing can begin, breaking it into smaller packets buys you
nothing.  

--

Rick "rickman" Collins

snipped-for-privacy@XYarius.com
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Re: Embedded Ethernet

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Noise margin.

A device designed for only 10 Mbit/s can have a much narrower
frequency response without destroying the eye pattern (ISI) than 100
Mbit/s. The narrow frequency rejects much of the high frequency noise
that might corrupt the 100 Mbit/s link. A narrow transceiver bandwidth
also reduces cable radiation, which can be important in some
situations. Don't use any data rates higher than necessary.

Paul


Re: Embedded Ethernet

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... and power consumption. YMMV but it seems that 100 Mbit/s
chips require roughly three times the power of 10 Mbit/s chips.

- Ville

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Ville Voipio, Dr.Tech., M.Sc. (EE)

Re: Embedded Ethernet
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... snip ...
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                  ^
This showed up some latencies here.  It took about two minutes to
figure out that your intent was "know".  Something about well worn
internal paths :-)

--
Chuck F ( snipped-for-privacy@yahoo.com) ( snipped-for-privacy@worldnet.att.net)
   Available for consulting/temporary embedded and systems.
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Re: Embedded Ethernet

[...]
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A 12.5 persent increase in throughput achied by increasing the
bandwith by a whopping 900 (in words: nine _hundred_) percent.  Which,
as as other posts in this thread confirmed, may well have come with a
200 percent penalty on the energy consumption.  Unless the application
very strictly needs exactly those 100 kByte/s, that's about as good an
example of wasted resources as any.

Actually, that increase in overall throughput is quite likely not even
caused by the increase in bandwith, but rather by the lower latency of
the line.

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How much more?

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That's not exaclty a new question.  Not in the context of this thread
at least.  The assumption from early on in it was that the micro
almost certainly *won't* be able to do anything useful with the
additional bandwidth.


--
Hans-Bernhard Broeker ( snipped-for-privacy@physik.rwth-aachen.de)
Even if all the snow were burnt, ashes would remain.

Re: Embedded Ethernet
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That's what I intended to confirm, nothing else.


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12 Mbpb, form a short guess. I should also note, that the
ATmega is currently running at 14,7 Mhz. Overclocking at
18 Mhz should be possible and there may be faster chips
available in the near future. No idea, if faster 8-bit
micros are available from other vendors. What I wanted to
say is, that the 8-bit micros already reached the limit
and will pass it sooner or later.


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One idea that came up in the Ethernut mailing list was, to
use a CPLD for DMA between SRAM and the NIC. That would free
the CPU from the main workload.

Harald

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Re: Embedded Ethernet

[...]
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A 12.5 persent increase in throughput achieved by increasing the
bandwith by a whopping 900 (in words: nine _hundred_) percent.  Which,
as as other posts in this thread confirmed, may well have come with a
200 percent penalty on the energy consumption.  Unless the application
very strictly needs exactly those 100 kByte/s, that's about as good an
example of wasted resources as any.

Actually, that increase in overall throughput is quite likely not even
caused by the increase in bandwith, but rather by the lower latency of
the line.

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How much more?

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Well, it's not exactly a new question.  Not in the context of this
thread at least.  The assumption from early on in it was that the
micro almost certainly *won't* be able to do anything useful with the
additional bandwidth.


--
Hans-Bernhard Broeker ( snipped-for-privacy@physik.rwth-aachen.de)
Even if all the snow were burnt, ashes would remain.
--
Hans-Bernhard Broeker ( snipped-for-privacy@physik.rwth-aachen.de)
Even if all the snow were burnt, ashes would remain.

Re: Embedded Ethernet
I got the Xport last week from Powercorp in Sydney. Very cool stuff. Soo
small. They are selling them as hot cakes and I was told I got the last one
for now.

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network
series
auto
of
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Re: Embedded Ethernet
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You forget the suits.

Being able to put "100 MBit/s capable" into the glossy feature sheet may
be a sales advantage. Even though it doesn't make much sense
technically...


--
Olav W÷lfelschneider                 snipped-for-privacy@wosch.teratronik.com


Re: Embedded Ethernet
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Craig

The RTL8019 AS is 5 V only making it not the ideal candidate if you
have a 3.3V CPU. Another option is the Cyrrus logic cs8900a which is
also just 10Mb but available in a 3.3V variant. There is a 100MB chip
with ISA interface available from SMSC. The partnumber is something
like 9xxxx. You should easily find it if you browse their pages.

HTH

Markus

Re: Embedded Ethernet
There is a 3.3V and 5V version of the MCU he's using.

I was looking at SMSC, however the bus looks like it's 16 bits data... is
there an 8bit mode?

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Re: Embedded Ethernet
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Hello all

I was just wondering if anyone had been able to get small quantities of
SMSC parts and where from?
I tried the local rep a while ago, but the minimum quantity was too
high; 360 from memory for a multi-io chip.

Regards
Paul Bealing
www.pmb.co.nz


Re: Embedded Ethernet
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Here in the US it looks like I can order 1 of the LAN91C111NC from
Nuhorizons for $24.  Sometimes when you try to order small quantities,
only then do they tell you about minimums.  Can you order on the web
from the US?  

http://nunext.nuhorizons.com/NuNext/servlet/NUHOnlineOrderingPartSearch?mode=Search

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Rick "rickman" Collins

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Re: Embedded Ethernet

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For 10BASE-T, the SMSC LAN91C96 is a simpler and lower power alternative to
LAN91C111.

Tauno Voipio
tauno voipio @ iki fi



Re: Embedded Ethernet
There is a device out there that embeds a complete 10/100 interface,
including a '186 micro, all the stacks etc into the Ethernet connector
socket. Around AUS$75, probably around US$35. pricey, but simple, and
very elegant.

the ad was in aaa local trade paper, I don't have that issue, but if you
still need it I'll post it back. I think Circuit cellar ran an article
using the same part in the last 2-3 months.

Al

Craig Rodgers wrote:
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Re: Embedded Ethernet

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Don't forget living with the single source nature of the part as well.  A
different PHY might be easier to handle than a whole new connection scheme.


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