docs: Add reference for Thumb2 inline assembler.

Thanks to Peter Hinch for contributing this.

1 files changed, 21 insertions, 0 deletions

diff --git a/docs/reference/asm_thumb2_str.rst b/docs/reference/asm_thumb2_str.rst
new file mode 100644
index 0000000000..5a88b091bd
--- /dev/null
+++ b/docs/reference/asm_thumb2_str.rst
@@ -0,0 +1,21 @@
+Store register to memory
+========================
+
+Document conventions
+--------------------
+
+Notation: ``Rt, Rn`` denote ARM registers R0-R7 except where stated. ``immN`` represents an immediate
+value having a width of N bits hence ``imm5`` is constrained to the range 0-31. ``[Rn + imm5]`` is the
+contents of the memory address obtained by adding Rn and the offset ``imm5``. Offsets are measured in
+bytes. These instructions do not affect the condition flags.
+
+Register Store
+--------------
+
+* str(Rt, [Rn, imm7]) ``[Rn + imm7] = Rt`` Store a 32 bit word
+* strb(Rt, [Rn, imm5]) ``[Rn + imm5] = Rt`` Store a byte (b0-b7)
+* strh(Rt, [Rn, imm6]) ``[Rn + imm6] = Rt`` Store a 16 bit half word (b0-b15)
+
+The specified immediate offsets are measured in bytes. Hence in the case of ``str`` the 7 bit value
+enables 32 bit word aligned values to be accessed with a maximum offset of 31 words. In the case of ``strh`` the
+6 bit value enables 16 bit half-word aligned values to be accessed with a maximum offset of 31 half-words.