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Old 02-23-2006, 02:26 PM
Nicolas Matringe
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Default ARCnet interface gate count

Hello all
I am trying to estimate the size of a project which will include an
ARCnet interface.
I don't have access to the ARCnet spec (not freely available) at the
moment so I can not give any number.
If anyone has good pointers or a quick rule of thumb...
Thanks in advance
Nicolas
PS don't tell me I will need the spec, I already know )

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Old 02-24-2006, 12:43 AM
Allan Herriman
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Default Re: ARCnet interface gate count

On 23 Feb 2006 05:26:19 -0800, "Nicolas Matringe" <[email protected]>
wrote:

>Hello all
>I am trying to estimate the size of a project which will include an
>ARCnet interface.
>I don't have access to the ARCnet spec (not freely available) at the
>moment so I can not give any number.
>If anyone has good pointers or a quick rule of thumb...
>Thanks in advance
>Nicolas
>PS don't tell me I will need the spec, I already know )


A *very rough* estimate would be to look at the size of a 10Base-2
Ethernet Phy + MAC. Sure, the implementation will be totally
different, but the basic functions and speed are equivalent.

You may need a few k bytes of buffer ram, but this may be shared with
your system ram if you're short of chip area.

IIRC, Arcnet drives a rather large signal (some V p-p) into a 93 ohm
cable. You will probably need a heavy duty driver just to get the
current. It may turn out to be more cost effective to use a separate
chip for that. The last time I designed one of these, I used a
fastish opamp (LM6061?) and an LH0002 to drive the cable. That was
for a one-off, cost-insensitive project.

Regards,
Allan
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  #3 (permalink)  
Old 02-24-2006, 11:10 AM
Nicolas Matringe
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Default Re: ARCnet interface gate count

Allan Herriman a écrit:
> A *very rough* estimate would be to look at the size of a 10Base-2
> Ethernet Phy + MAC. Sure, the implementation will be totally
> different, but the basic functions and speed are equivalent.


Sounds good... )


> You may need a few k bytes of buffer ram, but this may be shared with
> your system ram if you're short of chip area.


I'm in the preliminary phase of the project (feasability study,
actually). I get some inspiration from SMSC's COM20020 datasheet. This
chip has 2Kbytes of RAM.


> IIRC, Arcnet drives a rather large signal (some V p-p) into a 93 ohm
> cable. You will probably need a heavy duty driver just to get the
> current.


Still following SMSC's datasheet... Their evaluation board uses an
HYC9088 as physical interface so I guess I'll use it too.

Thanks a lot
Nicolas

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