[A83] Re: Weird commands

To: assembly-83@lists.ticalc.org
Subject: [A83] Re: Weird commands
From: "Dan Weiss" <dwedit@hotmail.com>
Date: Sat, 03 Nov 2001 20:26:27 -0600
Reply-To: assembly-83@lists.ticalc.org



>From: "Jimmy Pardey" <j_pardey@hotmail.com>
>Subject: [A83] Weird commands
>
>HellO! Why does the z80 have commands to load registers into themselves?
>Does it change the flags around or something?
>
>examples:   ld a,a
>             ld b,b

Because of the way the procesor decodes instructions:
LD A,r   = $78 + rb

  Reg   regbits
   A   =   7
   B   =   0
   C   =   1
   D   =   2
   E   =   3
   H   =   4
   L   =   5
((HL)  =   6 )

And they don't change flags.  They're basicly nops.

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