Embedded Ethernet in VHDL? 
Author Message
 Embedded Ethernet in VHDL?

I am about to start trying to implement an 10BaseT Ethernet controller
onto a CPLD or 8051 device (or maybe a combination of both).  VHDL is
what I know but i'm not sure if this project is too complex for a full
CPLD solution.

I've looked at the website www.embeddedethernet.com and it shows a
circuit diagram for use with it's own ethernet chip, There is a part
that the 4 RJ45 pins pass through before going into the chip, the
manufacturers website calls it an 'ethernet transformer' and has no
other info.  The device has no power supply. Does anyone know exactly
what this is or what it does?

Also has anyone got any references about the format/timing of the data
on the CAT 5 cable? Something more simple than me reading the 1500
page IEEE 802 standards!

Matt



Sun, 28 Mar 2004 20:32:21 GMT  
 Embedded Ethernet in VHDL?

Quote:
> I've looked at the website www.embeddedethernet.com and it shows a
> circuit diagram for use with it's own ethernet chip, There is a part
> that the 4 RJ45 pins pass through before going into the chip, the
> manufacturers website calls it an 'ethernet transformer' and has no
> other info.  The device has no power supply. Does anyone know exactly
> what this is or what it does?

This part is an transformer with 1:1   1:sqrt(2)  or 1:2  turns ratio.
It provides galvanic isolation between the net and the local electronics.
It needs no power supply because it is only a simple transformer (two
very long wires wound around a piece of ferrite). Just use the
recommmended type for your ethernet PHY it and dont think about it.

Quote:

> Also has anyone got any references about the format/timing of the data
> on the CAT 5 cable? Something more simple than me reading the 1500
> page IEEE 802 standards!

Hmm ...

dont know.

-Manfred



Mon, 29 Mar 2004 00:13:04 GMT  
 Embedded Ethernet in VHDL?


Quote:
> I am about to start trying to implement an 10BaseT Ethernet controller
> onto a CPLD or 8051 device (or maybe a combination of both).  VHDL is
> what I know but i'm not sure if this project is too complex for a full
> CPLD solution.

> I've looked at the website www.embeddedethernet.com and it shows a
> circuit diagram for use with it's own ethernet chip, There is a part
> that the 4 RJ45 pins pass through before going into the chip, the
> manufacturers website calls it an 'ethernet transformer' and has no
> other info.  The device has no power supply. Does anyone know exactly
> what this is or what it does?

Just as it says, it is commonly referred to as an ethernet transformer. It
connects the transmit and receive signal pairs to the ethernet controller,
and provides isolation and impedance matching. Note that the CS8900A (
www.cirrus.com ) has integrated filters for transmit and receive, you might
have problems implementing these in a CPLD. You can get "filter magnetics"
from HALO, see their selection guides and follow up on the controller
manufacturer web sites for inormation on the functionality. AMD for example.

Depending on your application, you might use a PHY device to perform the low
level functions and remove that complexity from your design task. Intel
LXT908 is an example chosen at random, there are others you could look at.

Quote:

> Also has anyone got any references about the format/timing of the data
> on the CAT 5 cable? Something more simple than me reading the 1500
> page IEEE 802 standards!

Off hand, I don't have any links to point you to, but a bit of research
should uncover some. It really depends on where your interface is, whether
to a PHY device or elsewhere. You could do worse than read the *relevant*
sections of the 802.3 spec, most of the 1500 pages will not be relevant.

Have a look at www.opencores.org for details of their ethernet controller
core which uses external PHY with MII interface.



Mon, 29 Mar 2004 00:13:37 GMT  
 Embedded Ethernet in VHDL?

Quote:

> I am about to start trying to implement an 10BaseT Ethernet controller
> onto a CPLD or 8051 device (or maybe a combination of both).  VHDL is
> what I know but i'm not sure if this project is too complex for a full
> CPLD solution.

The digital part of the controller could fit in an FPGA,
but you can also buy one for a few dollars.

Quote:
> I've looked at the website www.embeddedethernet.com and it shows a
> circuit diagram for use with it's own ethernet chip, There is a part
> that the 4 RJ45 pins pass through before going into the chip, the
> manufacturers website calls it an 'ethernet transformer' and has no
> other info.  The device has no power supply. Does anyone know exactly
> what this is or what it does?

The analog line interface requires a transformer for isolation.

Quote:
> Also has anyone got any references about the format/timing of the data
> on the CAT 5 cable? Something more simple than me reading the 1500
> page IEEE 802 standards!

go to www.google.com and enter:
10BaseT ethernet controller

 --Mike Treseler



Mon, 29 Mar 2004 00:13:22 GMT  
 
 [ 4 post ] 

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