How can Spartan-6 interface with 10/100 Mb/s Ethernet?

Question

Hi, I read LogiCORE IP AXI Ethernet Lite MAC (v1.01.b), which says that the Ethernet interface is with 10Mb/s 100Mb/s. On its spec, I find that the maximum clock for Spartan xc6slx45t AXI4-lite 120 MHz (Target Fmax). I am puzzled about the two categories numbers. 120 MHz is only marginal higher than 100 Mb/s. How can it recover a 100 Mb/s data? Could you explain it to me? Thanks,

Russell · Accepted Answer

Consider what happens when you go from a serial interface (like in Ethernet ) to a parallel interface.  If you have a 1 bit wide interface at 100 Mb/s  interfacing to a 16 bit wide parallel interface, your parallel interface on ly needs to run at 6.25 Mb/s (100/16).  As long as the module that does the  serial to parallel conversion can keep up, the rest of the logic can run i n parallel and can be run much slower. thernet  ock for  two n it

GaborSzakacs · Answer

The PHY interface (MII) runs at 25 MHz for a 100 Mbps link. The AXI bus is much wider than even that interface, so it can easily deal with 1Gpbs Ethernet. Note that the 120 MHz limit is at the AXI interface and not the I/O side of the module.

How can Spartan-6 interface with 10/100 Mb/s Ethernet?

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