Delete comment from: Ken Shirriff's blog
Zilog’s Z80 CPU deserves a mention here. As far as I know it was the first CPU to sport a DAA instruction.
Unlike the X86’s DAA and DAS instructions, the Z80’s DAA instruction handles both addition and subtraction, through the use of a special N flag which is set by a subtraction operation and reset by an addition operation. It also has an RLD (rotate left decimal) and RRD (rotate right decimal) instruction that rotates the BCD digits (nibbles) left and right between the accumulator (register A) and the memory location addressed by register pair HL.
Feb 2, 2023, 4:05:58 AM
Posted to Understanding the x86's Decimal Adjust after Addition (DAA) instruction