RE: [ethmac]

[colin.renfrew@sli-institute.ac.uk]

Thanks Kevin, sounds good.

My design is for full-duplex only - most if not all current GbE products 
I've seen around are full-duplex only. It avoids a LOT of problems that 
you only get with half duplex! 

I guess my main concern with the opensource code is that it is designed 
for half-duplex operation and therefore contain much that I don't need, 
but it's much easier than starting from scratch! 

Does it make a difference what media is being used? I thought the MAC 
interface would be generic i.e. for copper or fiber. 

I've had a glance at the documents for the MAC designed here. Is there 
anything that details the architecture of the receiver? The most detailed 
I've found (for any MAC anywhere) is a diagram of the entire MAC. I 
have a reasonable idea of what the Rx unit should look like, but I'd like 
to know if I'm on the right track!

Cheers,
Colin



----- Original Message ----- 
From: "Kevin Kay" <Kevin.Kay@e... > 
To: <ethmac@o... > 
Date: Mon, 29 Jul 2002 10:28:28 -0400 
Subject: RE: [ethmac] 

> 
> 
> I assume that you are doing a copper interface, so your MAC would 
> have a 
> GMII interface (8-bits wide) to the PHY rather than a SERDES 
> (10-bits 
> wide, 8b/10b coded) interface (fiber).  While the gig-E mac is 
> similar 
> in principle, I think it is slightly different in implementation 
> due to 
> real-world timing constraints (8-bits wide MII, collision timing 
> different, etc). 
> 
> I'm not a gig-E expert, but I seem to remember some minimum packet 
> length requirements in half duplex mode in order to reliably detect 
> a 
> collision in the high data-rate environment of gig-E.  If the 
> packet to 
> be transmitted was not large enough, it had to be padded.  The gigE 
> requirement was larger than the 64 bytes for 100MBit stuff.  This 
> larger 
> min packet requirement did not apply in full duplex (since there 
> would 
> never be a collision). 
> 
> I'm sure there are many more differences than the 8-bit wide 
> interface 
> and the half-duplex packet size. 
> 
> I'm not an author of the opencores code, but I have studied it a 
> great 
> deal, and I think much of the MAC code would apply if you are doing 
> a 
> 10/100/1000 MAC (you would be using the 10/100 code and adding 
1000 
> support). 
> 
> In a nutshell, my opinion is that the opencores code would be a 
> great 
> place to start (especially if doing 10/100/1000), but it will take 
> more 
> than a few hours to modifiy for 1000 support (no free lunch). 
> 
> Regards, 
> Kevin 
> 
> -----Original Message----- 
> From: Colin 
> [/cgi-bin/post.cgi?cmd=new&to=colin%20dot%20renfrew%20at%20sli-
institute%20dot%20ac%20dot%20uk&msg=/ml-
archive/ethmac/msg00013.shtml] 
> Sent: Monday, July 29, 2002 12:43 PM 
> To: ethmac@o...  
> Subject: [ethmac] 
> 
> 
> 
> Hi, 
>   I'm completely new to this forum. I'm currently working on a 
> project, 
> the focus of which is to design the MAC Rx for Gigabit Ethernet, in 
> Verilog. At the moment, I have still to begin actual implementation 
> and 
> coding. 
> 
> I stumbled across this mailing list and some of the information 
> I've 
> picked out so far looks invaluable to my project. I was wondering 
> if 
> anyone has general advice/can help me out with this. The main 
> question 
> I have on first glance at this mailing list is: Can all of this be 
> applied to 
> Gigabit Ethernet? If so, what are the main differences? 
> 
> Ok, any feedback would be greatly appreciated, 
> Cheers, 
> Colin 
> 
--
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