UM10429
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User manual
Rev. 1 — 20 October 2010
206 of 258
NXP Semiconductors
UM10429
Chapter 19: Appendix LPC1102 ARM Cortex-M0 reference
19.4.4.3.2
Operation
LDR, LDRB, U, LDRSB and LDRSH load the register specified by
Rt
with either a word,
zero extended byte, zero extended halfword, sign extended byte or sign extended
halfword value from memory.
STR, STRB and STRH store the word, least-significant byte or lower halfword contained
in the single register specified by
Rt
into memory.
The memory address to load from or store to is the sum of the values in the registers
specified by
Rn
and
Rm
.
19.4.4.3.3
Restrictions
In these instructions:
•
Rt
,
Rn
, and
Rm
must only specify R0-R7.
•
the computed memory address must be divisible by the number of bytes in the load or
store, see
.
19.4.4.3.4
Condition flags
These instructions do not change the flags.
19.4.4.3.5
Examples
STR
R0, [R5, R1]
; Store value of R0 into an address equal to
; sum of R5 and R1
LDRSH R1, [R2, R3]
; Load a halfword from the memory address
; specified by (R2 + R3), sign extend to 32-bits
; and write to R1.
19.4.4.4 LDR, PC-relative
Load register (literal) from memory.
19.4.4.4.1
Syntax
LDR
Rt
,
label
where:
Rt
is the register to load.
label
is a PC-relative expression. See
19.4.4.4.2
Operation
Loads the register specified by
Rt
from the word in memory specified by
label
.
19.4.4.4.3
Restrictions
In these instructions,
label
must be within 1020 bytes of the current PC and word aligned.
19.4.4.4.4
Condition flags
These instructions do not change the flags.