[Coco] [Color Computer] Re: VHDL 6809

[j_e_daggett]

--- In ColorComputer at yahoogroups.com, "John" <John0457 at h...> wrote:
> Hi James,
> 
> Sorry for the long delay in replying.
> I was wondering why I had not received any email from the list,
> and I just discovered it was going to my hotmail junk folder !!!
> Doh !!!
> 
> Anyway ... I received an email a frew weeks back from a friend who 
> must be on this list, talking about the 6847 and the 68... whatever 
> it is ... Synchronous Address Multiplexer (SAM). I had a look at my 
> motorola Data book circa 1981, and it is a possibility coding that. 
> The SAM is more work than the 6847. The 6847 appears to be slaved 
> off the SAM. I guess it's something only one person can work on 
> though, so its a matter of me finding some time to sit down and code 
> it.
> 
> John.
>

John 

MC6847 was designed to be used stand alone or with the SAM Chip
MC6883. As the SAM ship is designed to work with 8bit processors and
VDU by useing a method of cyclce sharing. The biggest heartache of
doing it in VHDL and what will take up room is the address lines are
multiplexed between the CPU, the VDU and the refresh counter. 

james

> --- In ColorComputer at yahoogroups.com, "James Diffendaffer" 
> <jdiffendaffer at y...> wrote:
> > --- In ColorComputer at yahoogroups.com, "John" <John0457 at h...> wrote:
> > > Hi,
> > > 
> > > I just joined the group.
> > > I was wondering if anyone knew of any one implementing a CoCo
> > > in an FPGA. I have a 6809 VHDL core running the Flex operating 
> system.
> > > http://members.optushome.com.au/jekent/FPGA.htm
> > 
> > Several people have talked about it but I don't know if any are
> > working on it.  I considered it but the VDG would be kinda time 
> consuming.
> > If there were a 6847 clone in VHDL it would be easy.



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