5.6 DEF

Set a symbolic name on a register.

The DEF directive allows the registers to be referred to through symbols. A defined symbol can be used in the rest of the program to refer to the register it is assigned to. A register can have several symbolic names attached to it. A symbol can be redefined later in the program.

Syntax
.DEF Symbol=Register
Example
.DEF temp=R16 
.DEF ior=R0

.CSEG 
ldi temp,0xf0 ; Load 0xf0 into temp register 
in ior,0x3f ; Read SREG into ior register 
eor temp,ior ; Exclusive or temp and ior