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Regarding the Ethernet peripheral of the Spartan 3E FPGA specifically the SMSC LAN83C185 Ethernet chip. The task is to create our own interface between the PLB and the ethernet chip. So far, I've been basing it on the xps_ethernetlite_v4.00 controller. The physical connections of the controller only shows the MII signals. However, I also saw that there are other pins in the Ethernet chip such like the oscillator, vdd, vss, mode and etc. My question is: are those pins already implicitly connected or do we have to explicitly connect all pins of the ethernet chip?

Second question is, the controller said to send 7 preamble bytes. However, the SMSC datasheet shows that it only receives 2 bytes. Why is that so?

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The data sheet usually has a table of pins which indicates pin function and if it can be left not connected. See page 11 of the datasheet. Page 13 shows test0 and test1 may be left floating, as an example.

Vdd and Vss are required, since those are supply pins. Mode pins are usually pulled up or down to select the mode of the device, and oscillator is required in most cases in my experience. Read the datasheet from back to front. The vast majority of pins need to be connected to something, not always the FPGA.

Also, you can connect the mode pins to a couple of the FPGA gpio pins to set the mode from the firmware. Check your bank voltages first, though.

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