22 Apr
2024
22 Apr
'24
4:54 p.m.
On 4/22/24 12:18, Chuck Guzis via cctalk wrote:
I don't know if this applies to the Z80, but on
the 8080, 16-bit
increment/decrement is handled by a separate increment block (also used
to advance the P-counter and stack operations). Probably one of the
reasons that INX/DCX doesn't set any flags.
16-bit INC and DEC are indeed
handled by a separate block, which also
gets used to increment PC and decrement SP at the appropriate times.
Ken's page on the 4-bit ALU has a 'mapped' dieshot showing it. Ken
covers it operation in the blog article
https://www.righto.com/2013/11/the-z-80s-16-bit-incrementdecrement.html