George:
It strikes me that unless you already have all the other necessary support chips in hand, the use of the DS8390 may be a costly venture as compared to using some other type of solution. When you use the DS8390 solution you end up having to put a whole memory bank and memory interface controller out in front of the chip. This takes a lot of silicon which translates to cost.

On the other hand there are other chips such as the SMSC LAN91C111 that may be much easier to interface to an 8051 due to the ease with which they can be interfaced. See data sheet: http://www.smsc.com/main/datasheets/91c111.pdf This part incidently has 8K bytes of RAM on board which can be used to buffer receive and transmit packets. For small mode type applications such as an 8051 node this may actually be all you need. The 8051, which does not have any sort of capability to support DMA anyway, can simply use a software transfer loop to move the data into and out of the packet buffers on board the 91C111 chip.

There are also other standalone Ethernet controllers to look at as well that are far far easier to interface to an 8-bit processor. The CS8900 part number comes to mind. It is very well likely that the cost of deploying some other technology than the DS8390 will be less than the DS8390 implementation becasue of the stuff you have to put around the National chip. On the other hand if you have all those chips also in hand then it is another story.

One reason that the idea of interfacing an 8051 to an off-the-shelf NIC card is so popular is that the cost of these boards is so cheap! However the attractivness of this approach may be diminishing because the type of card that is very easy to interface to an 8051 is one with an ISA interface!! ....And we all know where that is today with virtually all cards today being PCI cards which are much more difficult to interface to the 8051.

You may also want to study the latest embedded Ethernet technology. For a very interesting concept look at this web page: http://www.lantronix.com/products/...index.html

It may even be possible for you to approach a company like Lantronix and discuss your "save the animals" effort with them and see if they would support your effort with donated components in exchange for publicity. You can very often find companies that will do this for a good cause. To them the cost of 50 or 100 modules is small for the potential publicity it can generate. Their cost for doing it is less than 30% of what you could save over if you had to purchase the modules at the retail level.

Michael Karas