ARM Processor Architecture: Features, Usage, Processor Models, Instructions, PSR Access, Register Usage, Example System

ARM Processor Arch

• The ARM processor has architecture of 32-bit.
• In ARM the memory is defined as follows:
– Byte means 8 bits
– Halfword means 16 bits (two bytes)
– Word means 32 bits (four bytes)
• The ARM processor has two types of instruction sets defined as,
– 32-bit ARM Instruction Set
– 16-bit Thumb Instruction Set

Usage
• It is suitable for low power devices
• It is also used in consumer electronics like mobile
phones, digital media, calculators and hard drives and
routers.

Processor Models
• There are in total seven basic operating modes of ARM:
1. System: This is a privileged mode which makes use of the registers same as
user mode.
2. Abort: It handles all types of memory access breaches.
3. User : This is an unprivileged mode in which most of the tasks run.
4. IRQ: It is entered whenever a low priority interrupt is elevated.
5. Undef: It handles undefined instructions.
6. FIQ: It is entered whenever a high priority interrupt is elevated.
7. Supervisor: It is entered on reset and whenever a software interrupt gets
executed.