ARM Architecture Reference Manual ARMv7-A and ARMv7-R edition

Assembler syntax
STRBT , [ {, #}] Offset: Thumb only
STRBT , [] {, #} Post-indexed: ARM only
STRBT , [], +/- {, } Post-indexed: ARM only
where:
See Standard assembler syntax fields on page A8-7.
The source register.
The base register. The SP can be used.
Instruction Details
+/- Is + or omitted if or the optionally shifted value of is to be added to the base
register value (add == TRUE), or – if it is to be subtracted (permitted in ARM code only,
add == FALSE).
The immediate offset applied to the value of . Values are 0-255 for encoding T1, and
0-4095 for encoding A1. can be omitted, meaning an offset of 0.
Contains the offset that is optionally shifted and added to the value of to form the
address.
The shift to apply to the value read from . If omitted, no shift is applied. Shifts applied
to a register on page A8-10 describes the shifts and how they are encoded.
The pre-UAL syntax STRBT is equivalent to STRBT.
Operation
if ConditionPassed() then
EncodingSpecificOperations(); NullCheckIfThumbEE(n);
offset = if register_form then Shift(R[m], shift_t, shift_n, APSR.C) else imm32;
offset_addr = if add then (R[n] + offset) else (R[n] - offset);
address = if postindex then R[n] else offset_addr;
MemU_unpriv[address,1] = R[t];
if postindex then R[n] = offset_addr;
Exceptions
Data Abort.
ARM DDI 0406B Copyright © 1996-1998, 2000, 2004-2008 ARM Limited. All rights reserved. A8-395