6545 CRT Controller design

[Brian Lyons]

I trying to add a video display to a 6502 based computer I built and
wish to use 6545 CRT controller chip.

I would like to use Transparent Addressing (PH1/PH2 Interleave) mode.
But have not found a schematic example of this on-line.

I think there was something published in a Synertek application note,
but I don't have it. There may also be details in CRT Controller
Handbook (by Gerry Kane) - published inn 1980.

Anybody have sample schematic of 6545 using Transparent Addressing
(PH1/PH2 Interleave) mode???


Thanks

 

[Allan Herriman]

On Thu, 16 Dec 2004 21:28:15 -0500, Brian Lyons <Nospam@nowhere.com>
wrote:

I trying to add a video display to a 6502 based computer I built and
wish to use 6545 CRT controller chip.

I would like to use Transparent Addressing (PH1/PH2 Interleave) mode.
But have not found a schematic example of this on-line.

I think there was something published in a Synertek application note,
but I don't have it. There may also be details in CRT Controller
Handbook (by Gerry Kane) - published inn 1980.

Anybody have sample schematic of 6545 using Transparent Addressing
(PH1/PH2 Interleave) mode???

I did this with a 6845 and 6809 twenty years ago. You need an address
mux to select which of the uP or 6845 addresses goes to the ram plus a
little bit of logic to make sure the uP and 6845 are operating with
the correct phase.

It's rather simple, so you should be able to design it yourself.

Regards,
Allan

 

[Pooh Bear]

Brian Lyons wrote:

I trying to add a video display to a 6502 based computer I built and
wish to use 6545 CRT controller chip.

I would like to use Transparent Addressing (PH1/PH2 Interleave) mode.
But have not found a schematic example of this on-line.

That'll be because something that old won't be found online most likely.

I think there was something published in a Synertek application note,
but I don't have it. There may also be details in CRT Controller
Handbook (by Gerry Kane) - published inn 1980.

Anybody have sample schematic of 6545 using Transparent Addressing
(PH1/PH2 Interleave) mode???

Why did you want to build a 6502 based computer btw ?


Graham

 

[Paul Burke]

Allan Herriman wrote:

I did this with a 6845 and 6809 twenty years ago.
I did it around 1985 too with 6809 and 6845.
Ha! Mine was almost the same (which should be a hint to the OP),
except that the MPU + 6845 clock was 1.875MHz

Looks like EVERYBODY designed the Dragon 32/ Tandy Color Computer...

Paul Burke

 

[Allan Herriman]

On Fri, 17 Dec 2004 16:08:21 +0000, Paul Burke <paul@scazon.com>
wrote:

Allan Herriman wrote:

I did this with a 6845 and 6809 twenty years ago.
I did it around 1985 too with 6809 and 6845.
Ha! Mine was almost the same (which should be a hint to the OP),
except that the MPU + 6845 clock was 1.875MHz

Looks like EVERYBODY designed the Dragon 32/ Tandy Color Computer...

It was a little different. Instead of 74xx157 multiplexers for the
video ram address, it used a crude hack with a tristate buffer (for
the 6809 address) and resistors (for the 6845 address).

Regards,
Allan.

 

[Mika Leinonen]

There is a quite a bit of 6502 based info online. www.6502.org

But not a lot of detail about 6545 schematics.

Try searching http://www.funet.fi/pub/cbm for schematics of Commodore
computers. If I remember correctly, some these use the 6545.

 

[Kryten]

BTW I also have a scan of an Elektor CRTC board design, circa 1982.
Let me know if you would like that.

 

[Kryten]

"Brian Lyons" <Nospam@nowhere.com> wrote in message
news:8067s0t1c22cmtjlkojs73k3jluqv20rje@4ax.com...

I went to that site earlier this week and sent an e-mail to the
contact address, but have not heard back yet.

The spam filter is set to delete everything except known contacts and
messages with certain keywords like "Acorn" or "6502", etc. try again with
6502 in the title.

 

[Kryten]

"Jeroen" <jayjay.1974@xs4all.nl> wrote in message
news:41c25450$0$74230$e4fe514c@news.xs4all.nl...

Isn't that the trick where the 6545 is clocked with the same clock as the
6502, but then inverted?
So the two chips can share the same memories
without the need of arbitration?

Yes it is.