UM10360 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2013. All rights reserved.
User manual Rev. 3 — 20 December 2013 664 of 841
NXP Semiconductors
UM10360
Chapter 34: Appendix: Cortex-M3 user guide
[Rn, #offset]
• Pre-indexed addressing
The offset value is added to or subtracted from the address obtained from the register
Rn. The result is used as the address for the memory access and written back into the
register Rn. The assembly language syntax for this mode is:
[Rn, #offset]!
• Post-indexed addressing
The address obtained from the register Rn is used as the address for the memory
access. The offset value is added to or subtracted from the address, and written back
into the register Rn. The assembly language syntax for this mode is:
[Rn], #offset
The value to load or store can be a byte, halfword, word, or two words. Bytes and
halfwords can either be signed or unsigned. See Section 34.2.3.5 “
Address alignment”.
Table 617
shows the ranges of offset for immediate, pre-indexed and post-indexed forms.
34.2.4.2.3 Restrictions
For load instructions:
• Rt can be SP or PC for word loads only
• Rt must be different from Rt2 for two-word loads
• Rn must be different from Rt and Rt2 in the pre-indexed or post-indexed forms.
When Rt is PC in a word load instruction:
• bit[0] of the loaded value must be 1 for correct execution
• a branch occurs to the address created by changing bit[0] of the loaded value to 0
• if the instruction is conditional, it must be the last instruction in the IT block.
For store instructions:
• Rt can be SP for word stores only
• Rt must not be PC
• Rn must not be PC
• Rn must be different from Rt and Rt2 in the pre-indexed or post-indexed forms.
34.2.4.2.4 Condition flags
These instructions do not change the flags.
Table 617. Offset ranges
Instruction type Immediate offset Pre-indexed Post-indexed
Word, halfword, signed
halfword, byte, or
signed byte
255 to 4095 255 to 255 255 to 255
Two words multiple of 4 in the
range
1020 to 1020
multiple of 4 in the
range -1020 to 1020
multiple of 4 in the
range 1020 to 1020
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