Cortex-A8 R2P2.pdf - ARM Information Center

Programmer’s Model2.9 Data typesThe processor supports the following data types:• doubleword, 64-bit• word, 32-bit• halfword, 16-bit• byte, 8-bit.Note• when any of these types are described as unsigned, the N-bit data value representsa non-negative integer in the range 0 to +2 N -1, using normal binary format• when any of these types are described as signed, the N-bit data value representsan integer in the range -2 N-1 to +2 N-1 -1, using two’s complement format.For best performance you must align these as follows:• word quantities must align with 4-byte boundaries• halfword quantities must align with 2-byte boundaries• byte quantities can be placed on any byte boundary.The processor provides mixed-endian and unaligned access support. See Chapter 4Unaligned Data and Mixed-endian Data Support for details.NoteYou cannot use LDRD, LDM, LDC, STRD, STM, or STC instructions to access 32-bit quantities ifthey are unaligned.2-18 Copyright © 2006-2008 ARM Limited. All rights reserved. ARM DDI 0344E