Re: BBR/BBS 65C02 instruction cycle counts

From: smf <smf_at_null.net>
Date: Wed, 29 Jun 2016 10:13:21 +0100
Message-ID: <dff3dbcb-4e51-20fc-6cb7-97cc7b1eabf1@null.net>
This rockwell sheet is inconsistent: 
http://archive.6502.org/datasheets/rockwell_r65c00_microprocessors.pdf

On page 1-12, only the 6502 branches have (2) but the bbs/bbr don't
On page 1-11, both the 6502 branches and the bbs/bbr have **.

(2) & ** are +1 cycle if taking branch to same page, +2 if taking branch 
to different page.

If it were like the 6502 branches then I'd expect it to be 4/5/6, not 
5/6/7. As it would be 3 cycles to fetch the instruction, 1 cycle to 
fetch from zero page, 1 cycle if the branch was taken and another cycle 
if that branch crossed a page. Therefore I think page 1-12 is more 
likely to be correct and it always takes 5 cycles.

On 26/06/2016 09:12, Kajtár Zsolt wrote:
> * Rockwell sheet says 5/6/7 cycles.
>


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Received on 2016-06-29 10:00:07

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