ARM UsageFault Exception on RVDS4.1

If you compile code for ARM6 and later with RVDS/RVCT 4.1 compiler, it generates the VFP instructions by default. So, if you have not enabled VFP in your program, the UsageFault exception (for undefined exception) will occur. So, you have to assemble, compile and link your code by explicitly specifying the flag --fpu=none. The same applies when you find VFP instructions in the standard C library functions such as setjmp, longjmp.