ARM Alignment

On ARM-based systems you cannot address a 32-bit word that is not aligned to a 4-byte boundary 

LDR r0, = 0x1001
LDR r1, [r0]

The second line in the above code will give hard fault since are trying to read 4 bytes but the memory address is not divisible by 4

If we change the second line in above code to the following

LDRB r1, [r0];//Load 1 byte from address

The above line will not produce a hard fault, since we are trying to access 1 byte(1 byte can be accessed from any memory location)

Also notice the following example;

LDR r0,= 0x1002
LDRH r1,[r0];   //Load half word from 0x1002

References:

• https://lists.denx.de/pipermail/u-boot/2010-October/079003.html
• http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.faqs/ka15414.html