Honored Contributor
Honored ContributorDavid,
While I can't tell you how the soft MAC vs LAN91C111 hard MAC differs to the OS / Driver, I can tell you my experience with the device. Check out page 5 of the schematic below. It shows all the address lines connected up, but you don't need to connect all of them. The LAN91C111 responds to a base address of 0x300. There are many ways to write packet data into the chip. I chose to have a 32-bit data path (though, I believe you can use a 16 bit path as well). The entire address space of the chip is rather small in this configuration. Look at Chapter 8 in the LAN91C111 datasheet. I believe the entire space is only 16 locations. The chip uses a banking register to increase the space (performance limitation). I had an FPGA directly connected to the chip. I did not use a CPU, but instead chose to use a state machine to write data into the chip. It was pretty easy and I had a working setup in the lab in a week. But, to get to that point, I took the LAN91C111 datasheet everywhere I went and read it several times. There's source code out there too, and I imagine it would be pretty easy to write a driver for this device. One word of caution - there are throughput limitations. For my design, I didn't need a lot of throughput - a couple Mbps. But, if you are expecting to get the full line rate, you have some work to do. Please note that it has been years since I looked at this, so double check what I've said. Links to follow in another post....
