ARM Software reference manual

Chapter 2
23.1 [Rn,#off] is a pre-indexing addressing mode
Rn is the index register, modified by the 12-bit binary offset before it is
used. The calculated address Rn+offset is only written back to Rn if the Wb
bit is I. For example:
Action: LOAD/STORE to/from the indexed address
Then only if Wb=1:
An