Date   : Tue, 22 Sep 1998 18:54:20 +-200
From   : Carlo Concari <conca@...>
Subject: Re: 65C02 vs. 65C12 and Acorn ROMS

James Fidell wrote:

I was under the impression however that BBS and BBR *were* available on
the 65C12 and only SMB and RMB were 65C02 only.  Can anyone categorically
confirm or deny this ?  I've probably got all of the documentation that I
used for my CPU emulation somewhere, but half of my stuff is still in
cardboard boxes from when I moved.

Well, I have just tried my test program again and I can confirm that the 65C12
does not implement BBS, BBR, SMB, RMB.
I tried the following:
    EQUB &07
    LDA  #65
    JSR  &FFE3
    RTS
changing the EQUB &07 into &87, &0F, &8F but I always get to see the 'A' (if
the instruction were implemented, the 'A' could not be displayed).

I've done what I believe to be correct in my latest code.  All 65C12 NOPs
are single-byte and take one clock cycle.  For the other two CPUs it's not

That's not this way! My experimentations show that some of the NOPs take
multiple bytes (2 or 3) and many clock cycles (even 8!) I have posted the
timings for the instructions in one of my previous mails.
Well, this stands for my machine, but if you have chips made by others 
manufacturers they can be different, although I don't think so.


It's definitely got to be worth trying this one again.  To that ends,
I've set up an e-mail address bbc-micro-roms@...  If you want
the ROMs to be freely distributable, just drop an e-mail to that address
saying that you'd like the ROMS to be freely distributable.

Of course I'll do so :-)

Ciao to everybody,
Carlo.