ADD

Add the two operands and store their sum in the left operand.

Opcode	Bytes	Cycles	Form	Example
$88	3	3	add b:_, {byte}	add b:1, 123
$89	3	3	add p:_, {s_byte}	add p:2, 123
$d4	4	3	add p:_, {pair}	add p:2, 12345
$8a	3	3	add i:_, {s_byte}	add i:4, 123
$d5	4	3	add i:_, {s_pair}	add i:4, 12345
$8b	3	3	add b:_, b:_	add b:1, b:2
$8c	3	3	add p:_, p:_	add p:2, p:4
$8d	3	3	add i:_, i:_	add i:4, i:8
$3b	2	1	add sp, {s_byte}	add sp, 123
$8f	3	1	add sp, {s_pair}	add sp, 12345

Condition flag	Output
zero (ZF)	If the sum is zero, this flag is 1; otherwise it is 0.
negative (NF)	If the signed sum is a negative number, this flag is 1; otherwise it is 0.
overflow (OF)	If the sum exceeds the register's signed range, this flag is 1; otherwise it is 0.
carry (CF)	If the sum exceeds the register's unsigned range, this flag is 1; otherwise it is 0.

The condition flags are only modified when add is used with a framed register. For example, add sp, 123 or add ip, 123 will NOT affect any condition flags.

Notes

• If the previous instruction was with carry, and the left operand is a framed register, and CF is 1, then 1 is added to the sum. For example, with carry has no effect for the add sp, {s_byte} form.

• If io::stack_guard is 1, then add sp, {s_byte} and add sp, {pair} will trigger a stack fault event if the sp register becomes larger than the gp register.

Jump forms

Two forms of the jump pseudo-instruction are actually implemented as add instructions involving the ip register:

Opcode	Bytes	Cycles	Raw form	Jump example
$3c	2	1	add ip, {s_byte}	jump near $12_3abc
$90	3	1	add ip, {s_pair}	jump far $12_3abc