AHB SRAM or loading cause CDC/VCOM USB stop working in LPC4337

Discussion created by lpcware Employee on Jun 15, 2016
Latest reply on Jun 15, 2016 by lpcware
Content originally posted in LPCWare by jpplus on Thu Dec 11 01:55:48 MST 2014
I am using the ROM API CDC VCOM to develop a 4337 USB application.
The observations are:
1) when any code like memcpy access the AHB SRAM, USB stops working
2) when system loading is high, USB stop working. I have a DMA interrupt handler, USB can work correctly. But after I add more codes (basically computation complex stuff) in context of IRQ. Then USB stops.
USB stops means USB device show as a serial port in PC, and I uses some console app like Putty to receice data from this USB virutal serial port, but after accessing the AHB SRAM or adding computation complex stuff, there is no data can be receiced from Putty.

it is very strange, any ideas or hints are welcome.