Re: A86: Assembly Functions (RL, RR)

To: assembly-86@lists.ticalc.org
Subject: Re: A86: Assembly Functions (RL, RR)
From: Dan Eble <eble@cis.ohio-state.edu>
Date: Thu, 11 Sep 1997 12:22:14 -0400 (EDT)
In-Reply-To: <1.5.4.32.19970910213847.0091606c@mail.chipsnet.com>
Reply-To: assembly-86@lists.ticalc.org

On Wed, 10 Sep 1997, Ricci Adams wrote:

> 
>    Could somebody please explain the math behind the RL, RR, RLC, ect
> assembly functions.  I don't get it :)  The only ones I get are SLA and SRA :)
>                                 


RL is like SLA, except that the carry flag gets shifted into bit 0 of the
operand.  RR goes the opposite direction.  Here's a diagram:

              Rotate Left (RL)
       +------------------------------------------+
       |                                          |
     +---+    +---+---+---+---+---+---+---+---+   |
     | C |<---| 7   6   5   4   3   2   1   0 |<--+
     +---+    +---+---+---+---+---+---+---+---+

RLC is like RL, except that bit 7 gets shifted into bit 0 of the operand.
RRC goes the opposite direction.  Here's a diagram:

              Rotate Left Through Carry Flag (RLC)
            +-------------------------------------+
            |                                     |
     +---+  | +---+---+---+---+---+---+---+---+   |
     | C |<-+-| 7   6   5   4   3   2   1   0 |<--+
     +---+    +---+---+---+---+---+---+---+---+

--------
Dan Eble (mailto:eble@cis.ohio-state.edu)
         (http://www.cis.ohio-state.edu/~eble)

References:

A86: Assembly Functions (RL, RR)

From: Ricci Adams <ricci@chipsnet.com>