"Paramount among the concerns of embedded systems
developers is how to get the most processing power from the least
amount of electricity. The ARM processor family is one of the
better designs for balancing processor power and battery power
consumption.
"The ARM core has gained technology advances through several
versions over the last 20 years. Recent system on a chip (SoC)
processors running on mobile phones such as the T-Mobile G1 Android
combine dual-core (ARM9 and ARM11) processors to improve the
performance of multimedia applications on low-powered
platforms.
"The more recent ARM cores support two operational states: ARM
state, in which the core executes 32-bit, word-aligned
instructions, and THUMB state, which executes 16-bit,
halfword-aligned instructions. ARM mode provides the maximum power
and addressing range capability of the processor, whereas THUMB
mode allows portions of a program to be written in a very tight,
memory-conserving way that keeps memory costs low. Switching
between the modes is a trivial exercise, and for many algorithms,
the size of the code required can be reduced significantly."
