[A83] Re: Rotate 16 bits?

To: <assembly-83@lists.ticalc.org>
Subject: [A83] Re: Rotate 16 bits?
From: "Joe Pemberton" <joe@joepnet.com>
Date: Sun, 18 May 2003 10:08:01 -0700
References: <002601c31ccf$afc076e0$450456d1@D15FQS01>
Reply-To: assembly-83@lists.ticalc.org




> I would like to propose the following code for 16-bit 
> rotates. These are "in-place" rotates, with the carry
> bit set to the value of bit 15 for a rotate left, and 
> the value of bit 0 for a rotate right, i.e. analogous
> to the behavior of the RLC and RRC instructions.
> 
> ; rotate left, i.e. "RLC HL"
> 
> RLC H      ; rotate H left, CF = MSB of H
> RRC H      ; restore H by rotating right, CF = MSB of H
> ADC HL, HL ; LSB of L = old MSB of H, CF = old MSB of HL
> 

good thinking.. here's one that is 8 clocks faster but overwrites a:

[23 clocks]
ld a,h
rla
adc hl,hl

References:

[A83] Re: Rotate 16 bits?

From: "Wei Lin and Norbert Juffa" <juffa@earthlink.net>