ARM has 31 general purpose 32 bit register where 16 of these are visible at any time. Other registers are used to speed up processing of exceptions. There also is 6 32bit wide status registers. Lets see how it looks like. Registers are arranged in partially overlapping banks with a different register ban of each MCU mode. As I mentioned at any time 15 general purpose registers(R0 to R14) and one or two status registers and PC are visible.

Basically R0-R12 registers are user register, that doesn't have special purpose. Registers R13 – R15 has special functions. R13 is used as stack pointer (SP), R14 is used as link register (LR) and R15 is as program counter (PC):

One of the key features of the fast performance of ARM microcontrollers is Pipelining. ARM7 Core has three-stage pipeline that increase instruction flow through processor up to three times. So each instruction is executed in three stages:

• Fetch – instruction is fetched from memory and placed in pipeline;

• Decode – instruction is decoded and data-path signals prepared for next cycle;

• Execute – instruction from prepared data-path reads from registry bank, shifts operand to ALU and writes generated result to dominant register.

WinARM is a collection of GNU tools for ARM MCU family packed by Martin Thomas that works on MS Windows. WinARM is developed by inspiration on WinAVR project and it is really simple to start working with it if you had a chance to try WinAVR. WinARM doesn't depend on cygwin or mingw-environment like GNUARM tools does. WinARM toolset is compilled to work with most ARM microcontrollers including LPC2000 series, Atmel's ARM microcontrollers and Analog devices ARM microcontrollers as well. Basically tools should work with any microcontroller with ARM architecture.