Z80 DAA instruction

Question

Apologies for this seemingly minor question, but I can\'t seem to find the answer anywhere - I\'m just coming up to implementing the DAA instruction in my Z80 emulator, and I no

Answer 1

Just wanted to add that the N flag is what they mean when they talk about the previous operation. Additions set N = 0, subtractions set N = 1. Thus the contents of the A register and the C, H and N flags determine the result.

The instruction is intended to support BCD arithmetic but has other uses. Consider this code:

    and  15
    add  a,90h
    daa
    adc  a,40h
    daa

It ends converting the lower 4 bits of A register into the ASCII values '0', '1', ... '9', 'A', 'B', ..., 'F'. In other words, a binary to hexadecimal converter.