The program followed can't work in IAR 4.3:
unsigned char ch[3];
unsigned short int len,i;
for(i=0;i<3;i++) ch[i]=i+1; //set the value of array

//the following word compiled ok, but can't execut.
//dest: get a short int by ch[0] and ch[1] .
//like: len=ch[0]<<8 | ch[1];
len=*(unsigned short int *)ch ;

Hmm, thats interesting it doesnt work for the 4.40 either...

Hi,

try to align the character array to 32 bit then it should work (at least under gcc 3.x it worked).

But it really depends on the compiler, you cannot rely on it producing the correct code for that cast.

Reading the ARM docs will tell you why it doesn't work.