DAD Double Add Instruction
The contents of register RP are added to the contents of HL register pair and results of addition is stored in HL register pair. RP may be any of the register pair BC, DE, HL, or SP. The instruction format is
DAD RP ( HL - HL- +RP )
Flags: If result is larger than 16 bit the CY flag is set. No other flag are affected.