Assembly

If you are using the stack, the stackpointer should be initialized like this:

LDI R16, HIGH(RAMEND)
OUT SPH, R16
LDI R16, LOW(RAMEND)
OUT SPL, R16

Push data to the stack and decrease the stack pointer by one.

PUSH register

Load data from the stack and increase the stack pointer by one.

POP register

“Functions” in assembly.

Call a subrutine. The stack pointer is reduced by two.

CALL subrutine

Like >CALL by with relative a jump instead of absolute.

RCALL subrutine

Return from the subrutine. This uses the stack to know where it came from.

RET

Directives are resolved by the assembler, and therefore take zero clock cycles to resolve in the processor.

A name will be substituted with a number by the assembler.

.EQU name=nr

Same as >.EQU but can be reassigned.

.SET name=address

Alias for a register.

.DEF name=register

Sets the code address. The program will now execute from here.

.ORG address

Include other files. Mostly used to define values with >.EQU.

.INCLUDE file

Load a hardcoded value to a register.

Opcode: $1110\ \text{kkkk}\ \text{dddd}\ \text{kkkk}$

LDI reg value

Loads an 8-bit number into a register.

Opcode: $1001\ 000\text{d}\ \text{dddd}\ 0000\ \text{kkkk}\ \text{kkkk}\ \text{kkkk}\ \text{kkkk}$

Copy the content of a register to another.

MOV addr reg

Opcode: $0010\ 11\text{rd}\ \text{dddd}\ \text{rrrr}$

Increment a value in a register

INC Rd

Opcode: $1001\ 010\text{d}\ \text{dddd}\ 0011$

Add two registers togeather and place them in a third register.