The family of Cortex cores implements Thumb2 instruction set which is a superset of original Thumb instruction set. Thumb2 instruction set is a mixed 16/32bit instruction set， providing many 32-bit instructions which cover functionality of majority of 32-bit ARM instructions not covered by 16-bit Thumb instructions. Thumb2 instructions operate with standard ARM register configuration， allowing excellent interoperability between ARM and Thumb states. Using Thumb2 comes to an advantage in applications where code density is important. The availability of both ARM and Thumb2 instruction sets gives designers the flexibility to emphasize performance or code size on a subroutine level， according to the requirements of their applications. Cortex-M3 core implements Thumb2 instruction set only， while Cortex-R4 supports both ARM and Thumb2 instruction sets. Thumb2 Code Debugging Debugging of Thumb2 code is done in the same way as debugging ARM code. When Thumb2 code is being stepped， the Data in the Code window is 16/32 bits long， depending on instruction length; otherwise it is 32 bits long