Introduction to ARM

Instruction Syntax

<op>{cond}{flags} Rd, Rn, Operand2

<op>
A three-letter mnemonic, e.g. MOV or ADD.
{cond}
An optional two-letter condition code, e.g. EQ or CS.
{flags}
An optional additional flags. e.g. S.
Rd
The destination register.
Rn
The first source register.
Operand2
A flexible second operand.

Remarks

This is the general form of the arithmetic and logical instructions. Many instructions have a similar syntax to this, but are not identical.

In the syntax line, curly brackets indicate optional parts.

Leftmost register Rd is the destination.

Instructions are generally single-cycle (except write to PC and register-controlled shift).

There is a revised (external link) form of the assembly language, which ARM have recently introduced, called UAL (Unified Assembler Language). Among many other changes this allows the condition code to go after the flags.

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