[En-Nut-Discussion] SRAM speed

[Alastair Jeremy (E-mail)]

I agree with (1) regarding IC's available in industrial temperature ranges.
Although once you are in those sort of applications, you probably also
should be considering things such as CE mark, FCC & UL issues. I am NOT
actually suggesting that the Ethernut should be listed, but just try to
avoid a design feature that would preclude an Ethernut-based device from
ever being able to gain listing. On this topic I must profess that I am no
expert! So please, if anyone has any pointers, please let me know (ie... how
DO you design to meet these requirements?).

Also agree with (2), and looking at the OS structure, it would appear that
such drivers should be reasonably easy to slot in (although I'm sure Harald
would know more here). Also, Harald, you mentioned that you had previously
considered the 8900, but chose to go with another chip because of presumed
interrupt problems. I also previously investigated the 8900, and I assume
you are talking about the datasheet which says interrupts don't work in
8-bit mode (which is pretty much a killer if you want performance, since you
would need to poll the ethernet chip - ouch!). I have seen unofficial
suggestions that the interrupts _do_ actually work in 8 bit mode - do you
know what the reality is?  I think 10/100 (in a different chip entirely) is
a great idea, provided it is not too expensive.

I have never built a DMA circuit myself, but I was of the impression that it
would push the design requirements towards a FPGA, rather than a CPLD? Or
maybe I have been looking at the 'dumb' end of CPLDs.

Since you obviously have a fair bit of experience with the CPLD's, I have a
few more questions there too, but I will wait until I have them in a more
structured order...

Regards,

Alastair



-----Original Message-----
From: en-nut-discussion-admin at egnite.de
[mailto:en-nut-discussion-admin at egnite.de]On Behalf Of matt
Sent: Friday, 13 September 2002 3:55 AM
To: en-nut-discussion at egnite.de; Harald Kipp
Subject: Re: [En-Nut-Discussion] SRAM speed


I wouldn't rely on the very proprietary structure of FPSLIC . It is way too
expensive to survive , just a mega128 plus FPGA or CPLD adds up to less
money . IF and when the AVR core and peripherals get changed the changes are
small compared to what would happen to the system architecture if the FPSLIC
goes away so it doesn't look safe .

My company is interested in adopting Ethernut for embedded Ethernet
applications, and we're willing to assist with hardware development . I saw
another company showed a similar interest recently. Maybe we can come up
together with a relatively flexible solution that will benefit all Ethernut
users . We are open to discussion both on the list or private .

IF the Ethernet chip changes, would it be possible to:
-1- select IC's which are made in extended temperature range . Embedded
systems exist in industrial , communications and consumer products. Very few
consumer and a lot more industrial/communications though, so extended temp
makes sense at least as an option. This way even if regular boards were made
with commercial grade chips, extended temp would be possible by using the
same chip in industrial version. Atmel micros come in industrial and
commercial , Realtek doesn't . Crystal 8900a does for example .

-2- if several such Ethernet controllers are contemplated, what about a
dedicated driver for each, selected at compile time ?

-3- attempt to implement some sort of rudimentary DMA scheme going through
the FPGA/CPLD between the external RAM and the Ethernet controller ? This
would speed up transfers and throughput , and most of the time people don't
use up 100% of their FPGA/CPLD so it would come almost free (hardware extra
costs minimal) .

-4- regarding the CPLD/FPGA, we are familiar with the chips and devtools
from Atmel , Alterra, Xilinx, Lattice . They all make in circuit
programmable cpld's , and it would be possible to use a portion of the cpld
for the board address decoding, dma, etc and leave some free for the user .
Give the user the option of loading the programming file either directly
through ISP or JTAG , or through the mega128 itself , in which case it might
be in the form of an include file .

Best Regards,

Matt Tudor , MSEE
http://www.gigahertzelectronics.com


-----Original Message-----
From: Harald Kipp <harald.kipp at egnite.de>
To: en-nut-discussion at egnite.de <en-nut-discussion at egnite.de>
Date: Thursday, September 12, 2002 4:52 AM
Subject: RE: [En-Nut-Discussion] SRAM speed


>
>>Oh yes, and were you planning to have in-system programmable CPLD, to be
>>programmed by the ATmega? Or is that just a silly idea.
>
>Definitely this is _NOT_ a silly idea.
>
>Just in case somebody will now come up with
>FPSlic: Are you sure, that Atmel will continue
>to offer them to the public?
>
>Harald
>
>_______________________________________________
>En-Nut-Discussion mailing list
>En-Nut-Discussion at egnite.de
>http://www.egnite.de/mailman/listinfo/en-nut-discussion

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