ARM Processors

The ARM processor implements a low power, high performance 32 bit
RISC architecture.
It is being widely used in embedded devices such as mobile phones and PDAs (Personal
Data Assistants).
It has 31 32 bit registers with 16 visible in any mode.
Its instructions are simple load and store instructions (load a value from memory,
perform an operation and store the result back into memory).
One interesting feature it has is that every instruction is conditional.
For example, you can test the value of a register and, until you next test for
the same condition, you can conditionally execute instructions as and when you like.
Another interesting feature is that you can perform arithmetic and shift operations
on values as you load them.
It operates in several modes, including a system mode that can be entered from user mode
via a SWI (software interrupt).

It is a synthasisable core and ARM (the company) does not itself manufacture
processors. Instead the ARM partners (companies such as Intel or LSI for
example) implement the ARM architecture in silicon.
It allows other processors to be tightly coupled via a co-processor interface and
it has several memory management unit variations. These range from simple memory
protection schemes to complex page hierarchies.

� 1996-1999 David A Rusling copyright notice.