ARM VERSION 1.2 manual ADD and SUB, low registers, To +7, 255 to +255

Thumb Instruction Reference

5.2.1ADD and SUB, low registers

Add and subtract. There are three forms of these instructions that operate on low registers. You can:

•add or subtract the contents of two registers, and place the result in a third register

•add a small integer to, or subtract it from, the value in a register, and place the result in a different register

•add a larger integer to, or subtract it from, the value in a register, and return the result to the same register.

Syntax

op Rd, Rn, Rm

op Rd, Rn, #expr3 op Rd, #expr8

where:
op	is either ADD or SUB.
Rd	is the destination register. It is also used for the first operand in op
	Rd,#expr8 instructions.
Rn	is a register containing the first operand.
Rm	is a register containing the second operand.
expr3	is an expression evaluating (at assembly time) to an integer in the range
	–7 to +7.
expr8	is an expression evaluating (at assembly time) to an integer in the range
	–255 to +255.

Usage

op Rd,Rn,Rm performs an Rn + Rm or an Rn – Rm operation, and places the result in Rd.

op Rd,Rn,#expr3 performs an Rn + expr3 or an Rn – expr3 operation, and places the result in Rd.

op Rd,#expr8 performs an Rd + expr8 or an Rd – expr8 operation, and places the result in

Rd.

5-16 Copyright © 2000, 2001 ARM Limited. All rights reserved. ARM DUI 0068B