Ethernet chip - newbie need help with selection

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Hello all,
           I need a recommendation for an Ethernet chip.  I plan to integrate
it with an MCU (probably 8 bit).  Either a PIC or an AVR.  

I've heard of the Realtek 8019AS.  Is that a good chip to work with?  Is good
documentation and schematic examples available for it
(i've heard otherwise).  Is it considered a little dated given that its an
old chip?

If so, what others can you suggest?  I'd like to use a chip which has good
documentation/datasheets which I can refer to and more importantly
understand with ease.

I wish to gain the experience of making my own ethernet capable board,
writing my own tcp/ip stack so don't suggest any turnkey ("buy this board")
solutions.

Thank you very much to those who reply.  


Re: Ethernet chip - newbie need help with selection
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Although the Realtek 8019AS can be used, I consider it to be relatively
crappy.  It is doubtful that you will be able to get any useful information
on the chip from Realtek, since it was originally designed for the ISA bus
on standard PCs.  However, because there aren't that many Ethernet
controllers out there for embedded use, this non-PCI chip is relatively
popular.  The Microchip PICDEM.NET demo board's Users Guide has schematics
showing it in use.  Microchip App Note AN833 "The Microchip TCP/IP Stack"
may be useful if you're wondering how to interface with the Realtek's ISA
interface.  I would provide links to the afformentioned documents, but
unfortunately Microchip's website is down for maintenance right now.

The cons of this chip are:
1. High pin count wastes board space and increases soldering work
2. ISA bus requires bit banging, diminishing performance
3. Chip is old and costs a lot
4. Data sheet is gobbledygook and incomplete (for the purposes of doing
non-ISA-PC oriented designs)

The pros of this chip:
1. It exists
2. It works at 5V

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I'd recommend the Microchip ENC28J60 stand alone Ethernet controller with
SPI.  It's awesome compared to the 8019AS.  The only significant problem is
that the chip is new and Microchip's standard distributors don't appear to
have any chips to sell you at this point.  Unless you can wait, you may have
to contact Microchip to obtain chips to play with.

I've written a great deal of code for the ENC28J60 including my own TCP/IP
stack.  I like it.



Re: Ethernet chip - newbie need help with selection

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For micros with address and data bus there's nothing wrong with the deivce.
If you're into bit banging then perhaps the PCI variety may be more
appropriate.  They're also cheaper.  I'm talking of a couple of years ago
but I found an Asix part which was a Realtek lookalike with the same
registers etc.  The datasheet give you a second stab at understanding how to
drive the chip.

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 Worrying - I hate things you can't get!  It destroy any positive feature
the device might have.



Re: Ethernet chip - newbie need help with selection
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I may understand you wrong, but are you saying that bit-bangig an PCI
bus kind of networkcontroller is easier to bit bang with a smal micro
than an ISA bus one? Any reference/pointer of a project that does
this?

Markus

Re: Ethernet chip - newbie need help with selection
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I sense a growing frustration with the misuse of the term "bit banging"
leading to posts such as that quoted in the post above, which try to
illustrate that if you want to make the problem artificially hard for
yourself, you might as well enjoy it.

Interfacing an ISA bus peripheral to a typical microcontroller does not
require "bit banging"... at most it requires "strobe banging" if you
cannot match the ISA timing to some external memory or addressable I/O
mode of the device and have to use a general I/O pin to generate the
necessary strobes.

"Bit banging" implies you are using multiple I/O port accesses to send
or receive data one bit at a time - software implementations of serial
communications for example.


Re: Ethernet chip - newbie need help with selection
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According to wikipedia [ http://en.wikipedia.org/wiki/Bit_banging ], "bit
banging" generically means emulation of a hardware communication device in
software.  This does include your definition, but doesn't seem to imply that
I misused the term "bit banging".  The "atypical" microcontrollers I'm
familiar with (ones with low pin counts) don't have external memory buses,
so multiple I/O port access are needed to transfer data to and fro the ISA
device.  This admittedly is quite simple to do for ISA, which I did not know
when I posted.



Re: Ethernet chip - newbie need help with selection

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My immediate thought was that the PCI interface is a multiplexed address and
data bus.  Therefore with a limited number of IO pins it may have been
preferable to allow the controller to latch the address etc.  However some
ISA controllers have an I/O mode which saves on the range of addresses, so
perhaps there is little advantage.

I assumed bit-banging to be associated with I/O ports rather than with
standard address and data busses.



Re: Ethernet chip - newbie need help with selection

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Zilog eZ80F91. 50 MHz 8 bit MCU with on-chip 10/100 Ethernet controller. You
just have to add the phy with magnetics etc.

Mit freundlichen Grüßen

Frank-Christian Krügel

Re: Ethernet chip - newbie need help with selection
You might consider a Freescale hc9s12ne64 microcontroller with built in
ethernet MAC & PHY.  Basically all you have to add is a clock crystal,
ethernet magnetics, a bias resistor and the usual decoupling caps.

I know you wanted to write your own stack, but having opentcp readily
available for this chip at no charge gives you an easy way to test that
your board works.

One not nice thing: in the lower pin count version, you have no
complete 8 bit I/O ports!  Not sure what they were thinking - who wants
various fractions of multiple ports?  Have to go to the larger pin
count version to get some full width ports, or split byte-wide
peripherals across ports.


Re: Ethernet chip - newbie need help with selection


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Using either the Crystal CS8900A or the Realtec8019AS chips is a good choice
for a few reasons. Goto www.edtp.com and you can grab hold of small boards
with these chips already on and magnetics choosen. Of the two? My choice of
use is Realtek. Its easier to write code for due to its better (in my
opinion), buffer mechanism.

You can also decide (or not), to buy Freds book (Networking &
internetworking with Microcontrollers), he lays bare both ethernet chips
with lots of descriptions of the inner workings and if you want to accept
all he has to offer in the book, the source code as well. A great book for
anyone 'starting' with any of these chips. Lots of software/examples already
out there.


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Ok. Don't buy the boards. But buy the book (I'm not a shareholder honest!).
I bought it ages ago and it jump started my ethernet experience, although I
had already used the CS8900A a few years back.

As someone else has already mentioned. The Microchip ENC28J60 device is
'sort-of' available. Contact a Microchip rep and you may be able to get
samples. I know that they are shipping parts but demand is high. This chip
is v.small and very powerfull. Only uses SPI interface to your PIC.  And if
you get stuck on your TCPIP stack, there's code available to nudge you
along.

Good luck
Jim
www.picmodules.com






Re: Ethernet chip - newbie need help with selection
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AT91SAM7X128 or AT91SAM7X256 integrates

* ARM7
* Ethernet MAC (with MII interface)
* 128/256 kB Flash
* 32/64 kB SRAM

You goet a lot of other peripherals like U(S)ART, SPI, TWI, ADC, Timers etc.

--
Best Regards,
Ulf Samuelsson
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Re: Ethernet chip - newbie need help with selection
On Fri, 21 Oct 2005 01:50:09 -0600, zilinxchip

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The Wiznet W3100A is very easy to interface to an 8-bit MCU. Since the
TCP/IP stack is run in hardware on the chip (4 simultaneous sockets),
the amount of code needed is extremely small. The device only needs a
phy plus magnetics. They even have a development board with an
ATMEGA128 together with the W3100A.

Regards
  Anton Erasmus


Re: Ethernet chip - newbie need help with selection
Why do so many of the "ethernet chip" solutions still require a
seperate PHY?

Does making a PHY suggest a different semiconductor process?  It
certainly can be integrated with the rest of the ethernet functionality
or even a whole microcontroller, since a few like Freescale have done
it.


Re: Ethernet chip - newbie need help with selection

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Possibly because not everything ethernet is 10/100 UTP.

That not all PHY's are created equal.

That ethernet market forces have changed dominant PHY's several times
over the years.

Read the MC9S12NE64 data sheet and note the lengths Freescale goes to
detail exactly how to bypass the built-in PHY.

Its nice to have the PHY built in, less work. But there are also
heat/power and isolation issues where it helps to have the PHY outboard.

Re: Ethernet chip - newbie need help with selection

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Hi Ulf,

Do Atmel do any "automotive" rated (105 deg C) parts?

--

John Devereux

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