I am using FX2LP in slave fifo mode for USB integration with the FPGA on a custom board. The USB controller works fine for small to medium transactions. If I try back to back bulk writes (each of 1M Bytes), the controller becomes non responsive. I can see the transactions being posted by the host, but the FPGA never gets any response from slave fifos. The problem suddenly disappears if I try a smaller write. Then for some time, the larger writes will work and again will run into a halt after a few write cycles.
Any suggestions what's going wrong the FX2LP ?
Have you hooked up a CATC analyzer to see what is happening on the bus.
I've seen issues when big transfer (1MB is big when you push it to host controller is one shot) are triggered due to host controller buffer limitation. CATC trace should tell us if the data is even going to the FX2LP or not.