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

Assembler syntax
LDRB , Normal form
LDRB , [PC, #+/-] Alternative form
where:
See Standard assembler syntax fields on page A8-7.
The destination register.
Instruction Details
The label of the literal data item that is to be loaded into . The assembler calculates the
required value of the offset from the Align(PC,4) value of this instruction to the label.
Permitted values of the offset are -4095 to 4095.
If the offset is zero or positive, imm32 is equal to the offset and add == TRUE.
If the offset is negative, imm32 is equal to minus the offset and add == FALSE.
The alternative syntax permits the addition or subtraction of the offset and the immediate offset to be
specified separately, including permitting a subtraction of 0 that cannot be specified using the normal
syntax. For more information, see Use of labels in UAL instruction syntax on page A4-5.
The pre-UAL syntax LDRB is equivalent to LDRB.
Operation
if ConditionPassed() then
EncodingSpecificOperations(); NullCheckIfThumbEE(15);
base = Align(PC,4);
address = if add then (base + imm32) else (base - imm32);
R[t] = ZeroExtend(MemU[address,1], 32);
Exceptions
Data Abort.
ARM DDI 0406B Copyright © 1996-1998, 2000, 2004-2008 ARM Limited. All rights reserved. A8-131