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, {SBYTE} form.

• If IO::STACK_GUARD is 1, then ADD SP, {SBYTE} 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