RTX with External SDRAM LPC1788 - causes bus fault

Hello,

I'm using the Embedded Artists LPC1788 development kit and I'm trying to get a very simple RTX application running using the external SDRAM.

Here is what I have so far:

1) A simple RTX application that runs (blinks an LED) with no problem when I use the internal RAM. This same application crashes with a bus fault in "os_sys_init" when I us the external SDRAM.

2) I configure and initialize the external SDRAM before the call to __main (this is working as I can run the same blinking LED using the SDRAM with no RTX.

3) Even if I let me STACK and HEAP remain in the internal RAM but have variables etc.. in the SDRAM I get the bus fault.

4) The bus fault is an IMPRECISERR: Imprecise data bus error

The call stack looks like this when the fault occurs:

HardFault_Handler -> rt_put_rdy_first() -> rt_dispatch() -> rt_task_create() -> SVC_Hanlder...

Does anyone have any suggestions? I see no reason why this should cause a fault.

Thanks.

MAC