Cyclone III development board and USB FT245BL

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but I just like to play with the USB chip on the devkit to see whether the latency of a USB connector would be feasible for my application

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For an FTDI-fifo application, even for the smallest write or read, you have to incorporate a latency of 1ms for writes, 2 milliseconds for reads. These are the minimum values that can be set in the driver. So you really must transfer big enough chunks of data before you get some interesting bandwidth.

Stefaan