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semi-ot: motorola 6847
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Tarkin
Jun 3, 2012, 3:23:37 AM6/3/12
to
Hiya folks,
I know Andrew Lynch of N8VEM fame was enquiring about the
NEC upd7220 a few years back. I am researching something similar...
Context:
I know I've read more than once where some people find using a pc
as a serial terminal to a cp/m SBC or system a "waste".
Noting that older crt-based serial terminals are dying off, I've
been
researching ways to drive NTSC (or PAL...) TVs and compatible LCDs
(don't laugh, small ones for camera interface are around 20USD...)
from a micro controller...
The best of the micro controller designs I've seen use two PICs- one
to process and drive data to the second, which produces line signals.
I was going back in time, so to speak, to see how this particular
wheel
was carved before...and I ran across references to the Motorola 6845
and 6847.
So...my questions are:
A) Is the 6845 even feasible as a video signal generator? It seems
more like a glorified DRAM refresh controller...
B) Can the 6847 be used standalone, without an r/f modulator?
I.E., can one simply tap the Y output for monochrome video, and/or
Y + ϕA + ϕB for color (S-Video)?
TIA,
Tarkin
I know Andrew Lynch of N8VEM fame was enquiring about the
NEC upd7220 a few years back. I am researching something similar...
Context:
I know I've read more than once where some people find using a pc
as a serial terminal to a cp/m SBC or system a "waste".
Noting that older crt-based serial terminals are dying off, I've
been
researching ways to drive NTSC (or PAL...) TVs and compatible LCDs
(don't laugh, small ones for camera interface are around 20USD...)
from a micro controller...
The best of the micro controller designs I've seen use two PICs- one
to process and drive data to the second, which produces line signals.
I was going back in time, so to speak, to see how this particular
wheel
was carved before...and I ran across references to the Motorola 6845
and 6847.
So...my questions are:
A) Is the 6845 even feasible as a video signal generator? It seems
more like a glorified DRAM refresh controller...
B) Can the 6847 be used standalone, without an r/f modulator?
I.E., can one simply tap the Y output for monochrome video, and/or
Y + ϕA + ϕB for color (S-Video)?
TIA,
Tarkin
Torfinn Ingolfsen
Jun 3, 2012, 4:21:02 AM6/3/12
to
On 06/03/2012 09:23, Tarkin wrote:
> Context:
> I know I've read more than once where some people find using a pc
> as a serial terminal to a cp/m SBC or system a "waste".
>
> Noting that older crt-based serial terminals are dying off, I've
> been
> researching ways to drive NTSC (or PAL...) TVs and compatible LCDs
> (don't laugh, small ones for camera interface are around 20USD...)
> from a micro controller...
Great! Kind of the way PockeTerm works:
> Context:
> I know I've read more than once where some people find using a pc
> as a serial terminal to a cp/m SBC or system a "waste".
>
> Noting that older crt-based serial terminals are dying off, I've
> been
> researching ways to drive NTSC (or PAL...) TVs and compatible LCDs
> (don't laugh, small ones for camera interface are around 20USD...)
> from a micro controller...
http://www.brielcomputers.com/wordpress/?cat=25
except that it uses "normal" LCD monitors with VGA input.
> The best of the micro controller designs I've seen use two PICs- one
> to process and drive data to the second, which produces line signals.
microcontrollers out there.
> A) Is the 6845 even feasible as a video signal generator? It seems
> more like a glorified DRAM refresh controller...
> B) Can the 6847 be used standalone, without an r/f modulator?
> I.E., can one simply tap the Y output for monochrome video, and/or
> Y + ϕA + ϕB for color (S-Video)?
Any fast enough microcontroller with enough pins can do it, using
resistors as a D/A converter.
For both composite and VGA output. Some example quickly found with Google.
Arduino:
http://arduino.cc/playground/Main/TVout
http://little-scale.blogspot.no/2008/02/hacking-vga-lines-with-arduino.html
http://avga.prometheus4.com/index.php?p=2-3
http://linusakesson.net/scene/craft/index.php
Propeller:
http://forums.parallax.com/showthread.php?140426-VGA-using-8-bits-RRRGGGBB-HS-amp-VS-10-pins-Anyone-tried-it&p=1102275&viewfull=1#post1102275
http://linusakesson.net/scene/turbulence/index.php
http://wardyprojects.blogspot.no/2011/12/propeller-tv-out-demo.html
HTH
--
Torfinn Ingolfsen,
Norway
glen herrmannsfeldt
Jun 3, 2012, 10:10:14 AM6/3/12
to
Tarkin <tark...@gmail.com> wrote:
(snip)
IBM PC. Yes DRAM refresh is a side result. It was a favorite
side-effect of many on-board video display circuits to also
refresh the DRAM.
Pretty similar to many other video display systems of the time.
You can generate text by sending the bytes to a character ROM
and shift register, or graphics by sending directly to the shift
register.
> B) Can the 6847 be used standalone, without an r/f modulator?
Yes.
> I.E., can one simply tap the Y output for monochrome video, and/or
> Y + ??A + ??B for color (S-Video)?
I believe not. Well, the video clock is a multiple of the NTSC
color subcarrier, so the colors are actually a side effect.
But not quite the same as the CGA, which also worked that way.
In the highest resolution, though, it is monochrome and works
will with a black and white monitor or TV.
The 6847 was the basis for the TRS-80 color computer.
That, and the 6883 along with the 6809 were pretty much used
as designed by Motorola. I believe the 6847 works without the
6883, but I am not completely sure about that.
-- glen
(snip)
> Noting that older crt-based serial terminals are dying off, I've
> been researching ways to drive NTSC (or PAL...) TVs and
> compatible LCDs (don't laugh, small ones for camera interface
> are around 20USD...) from a micro controller...
(snip)
> been researching ways to drive NTSC (or PAL...) TVs and
> compatible LCDs (don't laugh, small ones for camera interface
> are around 20USD...) from a micro controller...
> I was going back in time, so to speak, to see how this particular
> wheel was carved before...and I ran across references to the
> Motorola 6845 and 6847.
> So...my questions are:
> A) Is the 6845 even feasible as a video signal generator?
> It seems more like a glorified DRAM refresh controller...
Yes. The 6845 is the basis for the MCA and CGA of the original
> wheel was carved before...and I ran across references to the
> Motorola 6845 and 6847.
> So...my questions are:
> A) Is the 6845 even feasible as a video signal generator?
> It seems more like a glorified DRAM refresh controller...
IBM PC. Yes DRAM refresh is a side result. It was a favorite
side-effect of many on-board video display circuits to also
refresh the DRAM.
Pretty similar to many other video display systems of the time.
You can generate text by sending the bytes to a character ROM
and shift register, or graphics by sending directly to the shift
register.
> B) Can the 6847 be used standalone, without an r/f modulator?
> I.E., can one simply tap the Y output for monochrome video, and/or
I believe not. Well, the video clock is a multiple of the NTSC
color subcarrier, so the colors are actually a side effect.
But not quite the same as the CGA, which also worked that way.
In the highest resolution, though, it is monochrome and works
will with a black and white monitor or TV.
The 6847 was the basis for the TRS-80 color computer.
That, and the 6883 along with the 6809 were pretty much used
as designed by Motorola. I believe the 6847 works without the
6883, but I am not completely sure about that.
-- glen
Tarkin
Jun 3, 2012, 10:30:18 AM6/3/12
to
On Jun 3, 4:21 am, Torfinn Ingolfsen <ti...@home.no> wrote:
> On 06/03/2012 09:23, Tarkin wrote:
>
> > Context:
> > I know I've read more than once where some people find using a pc
> > as a serial terminal to a cp/m SBC or system a "waste".
>
> > Noting that older crt-based serial terminals are dying off, I've
> > been
> > researching ways to drive NTSC (or PAL...) TVs and compatible LCDs
> > (don't laugh, small ones for camera interface are around 20USD...)
> > from a micro controller...
>
> Great! Kind of the way PockeTerm works:http://www.brielcomputers.com/wordpress/?cat=25
> except that it uses "normal" LCD monitors with VGA input.
>
> > The best of the micro controller designs I've seen use two PICs- one
> > to process and drive data to the second, which produces line signals.
>
> Then you haven't look hard enough. There are a lot more than PIC
> microcontrollers out there.
>
yes....
> On 06/03/2012 09:23, Tarkin wrote:
>
> > Context:
> > I know I've read more than once where some people find using a pc
> > as a serial terminal to a cp/m SBC or system a "waste".
>
> > Noting that older crt-based serial terminals are dying off, I've
> > been
> > researching ways to drive NTSC (or PAL...) TVs and compatible LCDs
> > (don't laugh, small ones for camera interface are around 20USD...)
> > from a micro controller...
>
> Great! Kind of the way PockeTerm works:http://www.brielcomputers.com/wordpress/?cat=25
> except that it uses "normal" LCD monitors with VGA input.
>
> > The best of the micro controller designs I've seen use two PICs- one
> > to process and drive data to the second, which produces line signals.
>
> Then you haven't look hard enough. There are a lot more than PIC
> microcontrollers out there.
>
Propellers, to my mind, are actually more than one microcontroller.
The arduino is an entire board.
> > A) Is the 6845 even feasible as a video signal generator? It seems
> > more like a glorified DRAM refresh controller...
> > B) Can the 6847 be used standalone, without an r/f modulator?
> > I.E., can one simply tap the Y output for monochrome video, and/or
> > Y + ϕA + ϕB for color (S-Video)?
>
> You do not need a specialized chip to generate a video signal.
> Any fast enough microcontroller with enough pins can do it, using
> resistors as a D/A converter.
> For both composite and VGA output. Some example quickly found with Google.
>
>
> Propeller:http://forums.parallax.com/showthread.php?140426-VGA-using-8-bits-RRR...http://linusakesson.net/scene/turbulence/index.phphttp://wardyprojects.blogspot.no/2011/12/propeller-tv-out-demo.html
>
> HTH
> --
> Torfinn Ingolfsen,
> Norway
The Propeller may be worth a look, although it would make more sense
> HTH
> --
> Torfinn Ingolfsen,
> Norway
just to build the rest of a CP/M emulator with the remaining cores...
Thanks!
TTFN,
Tarkin
Roger Ivie
Jun 3, 2012, 11:29:58 AM6/3/12
to
On 2012-06-03, glen herrmannsfeldt <g...@ugcs.caltech.edu> wrote:
> The 6847 was the basis for the TRS-80 color computer.
The color computer and similar Dragon machines were pretty much
> The 6847 was the basis for the TRS-80 color computer.
right out of a Motorola app note for the 6883. I used to have
a copy of the app note; not sure how easy it is to find these days.
http://en.wikipedia.org/wiki/Dragon_32/64
> That, and the 6883 along with the 6809 were pretty much used
> as designed by Motorola. I believe the 6847 works without the
> 6883, but I am not completely sure about that.
that people used it as a drop-in replacement.
--
roger ivie
ri...@ridgenet.net
glen herrmannsfeldt
Jun 3, 2012, 12:25:41 PM6/3/12
to
Roger Ivie <ri...@ridgenet.net> wrote:
> On 2012-06-03, glen herrmannsfeldt <g...@ugcs.caltech.edu> wrote:
>> The 6847 was the basis for the TRS-80 color computer.
> The color computer and similar Dragon machines were pretty much
> right out of a Motorola app note for the 6883. I used to have
> a copy of the app note; not sure how easy it is to find these days.
> http://en.wikipedia.org/wiki/Dragon_32/64
I think I still have the CC service manual. I will have to
> On 2012-06-03, glen herrmannsfeldt <g...@ugcs.caltech.edu> wrote:
>> The 6847 was the basis for the TRS-80 color computer.
> The color computer and similar Dragon machines were pretty much
> right out of a Motorola app note for the 6883. I used to have
> a copy of the app note; not sure how easy it is to find these days.
> http://en.wikipedia.org/wiki/Dragon_32/64
dig it out.
>> That, and the 6883 along with the 6809 were pretty much used
>> as designed by Motorola. I believe the 6847 works without the
>> 6883, but I am not completely sure about that.
> IIRC, the 6847 is close enough to pin-compatible with the 6845
> that people used it as a drop-in replacement.
plus the 6845. I didn't remember them as being that close, but maybe.
The 6845 is more general purpose, though. All the timing is
programmable, where the 6847 has specific video modes.
-- glen
Torfinn Ingolfsen
Jun 3, 2012, 1:03:42 PM6/3/12
to
On 06/03/2012 16:30, Tarkin wrote:
> Propellers, to my mind, are actually more than one microcontroller.
Good enough. :)
> Propellers, to my mind, are actually more than one microcontroller.
> The arduino is an entire board.
Arduino) are capable of generating a video signal with very few external
components.
> The Propeller may be worth a look, although it would make more sense
> just to build the rest of a CP/M emulator with the remaining cores...
http://smarthome.jigsy.com/propeller
http://forums.parallax.com/showthread.php?117996-Dracblade-SBC-with-Catalina-C-PropBasic-CP-M-MP-M-TRS80-wireless-network
We live in interesting times :-)
--
Torfinn Ingolfsen,
Norway
Tarkin
Jun 3, 2012, 2:47:04 PM6/3/12
to
On Jun 3, 10:10 am, glen herrmannsfeldt <g...@ugcs.caltech.edu> wrote:
Tapping the Y output for monochrome composite?
Or are you saying I need more circuitry either way,
though not necessarily a 1372/1373?
(the 1372/1373 is mentioned in the datasheet, and is
what I meant by r/f modulator).
> The 6847 was the basis for the TRS-80 color computer.
Yes, the TRS-80, Dragon 32/64, Laser 200, and Acorn Atom,
according to Wikipedia. Hence, the appeal for my project-
this is a period-accurate tool.
> That, and the 6883 along with the 6809 were pretty much used
> as designed by Motorola. I believe the 6847 works without the
> 6883, but I am not completely sure about that.
>
It appears to, if Figure 23 of the Motorola datasheet is accurate.
The 6883 is sort of an all-in-wonder, providing clock, (I)DMA, and
refresh.
What troubles me is no figures showing an example system
without a 1372 :(
> -- glen
TTFN,
Tarkin
Or are you saying I need more circuitry either way,
though not necessarily a 1372/1373?
(the 1372/1373 is mentioned in the datasheet, and is
what I meant by r/f modulator).
> The 6847 was the basis for the TRS-80 color computer.
according to Wikipedia. Hence, the appeal for my project-
this is a period-accurate tool.
> That, and the 6883 along with the 6809 were pretty much used
> as designed by Motorola. I believe the 6847 works without the
> 6883, but I am not completely sure about that.
>
The 6883 is sort of an all-in-wonder, providing clock, (I)DMA, and
refresh.
What troubles me is no figures showing an example system
without a 1372 :(
> -- glen
TTFN,
Tarkin
Roger Ivie
Jun 4, 2012, 12:31:00 AM6/4/12
to
On 2012-06-03, glen herrmannsfeldt <g...@ugcs.caltech.edu> wrote:
> Roger Ivie <ri...@ridgenet.net> wrote:
>> IIRC, the 6847 is close enough to pin-compatible with the 6845
>> that people used it as a drop-in replacement.
>
> When I first got my CC, I ordered the data sheets for the chips,
> plus the 6845. I didn't remember them as being that close, but maybe.
I just realized I was thinking of the 6545, not the 6847.
>> IIRC, the 6847 is close enough to pin-compatible with the 6845
>> that people used it as a drop-in replacement.
>
> When I first got my CC, I ordered the data sheets for the chips,
> plus the 6845. I didn't remember them as being that close, but maybe.
--
roger ivie
ri...@ridgenet.net
Tarkin
Jun 4, 2012, 12:20:26 AM6/4/12
to
On Jun 3, 1:03 pm, Torfinn Ingolfsen <ti...@home.no> wrote:
> On 06/03/2012 16:30, Tarkin wrote:
>
> > Propellers, to my mind, are actually more than one microcontroller.
>
> Good enough. :)
>
> > The arduino is an entire board.
>
> The point was that the AVR 8-bit microcontrollers (as found on the
> Arduino) are capable of generating a video signal with very few external
> components.
>
> > The Propeller may be worth a look, although it would make more sense
> > just to build the rest of a CP/M emulator with the remaining cores...
>
> Already done, seehttp://smarthome.jigsy.com/propellerhttp://forums.parallax.com/showthread.php?117996-Dracblade-SBC-with-C...
> On 06/03/2012 16:30, Tarkin wrote:
>
> > Propellers, to my mind, are actually more than one microcontroller.
>
> Good enough. :)
>
> > The arduino is an entire board.
>
> The point was that the AVR 8-bit microcontrollers (as found on the
> Arduino) are capable of generating a video signal with very few external
> components.
>
> > The Propeller may be worth a look, although it would make more sense
> > just to build the rest of a CP/M emulator with the remaining cores...
>
>
I was trying to hint that I was already aware of the prior art ;^)
> We live in interesting times :-)
> --
> Torfinn Ingolfsen,
> Norway
TTFN,
Tarkin
Message has been deleted
Tarkin
Jun 4, 2012, 1:37:02 PM6/4/12
to
On Jun 4, 6:44 am, lynchaj <lync...@yahoo.com> wrote:
> Thanks! Yes, we did an uPD7220 board on the N8VEM project. It
> generates VGA compatible 640x480 and 800x600 color displays. It can
> use modern LCDs and the board includes a VGA compatible RAMDAC for a
> lot of color control. The project works nicely after 2 or 3 rounds of
> prototypes. It is all documented on the N8VEM wiki in the uPD7220
> folder under ECB IO boards.
>
> I still have several PCBs left. They are ECB boards but can easily be
> interfaced to any Z80 type home brew computer system. Please take a
> look at the pictures as the boards work really well and generate a
> nice display. They are "period authentic" full color displays using
> modern hardware.
>
> Any and all uPD7220 enthusiasts welcome! Thanks and have a nice day!
>
> Andrew Lynch
I'll have a look, thanks.
TTFN,
Tarkin
> On Jun 3, 3:23 am, Tarkin <tarkin...@gmail.com> wrote:
>
> > Hiya folks,
>
> > I know Andrew Lynch of N8VEM fame was enquiring about the
> > NEC upd7220 a few years back. I am researching something similar...
>
> Hi Tarkin
>
> > Hiya folks,
>
> > I know Andrew Lynch of N8VEM fame was enquiring about the
> > NEC upd7220 a few years back. I am researching something similar...
>
> Thanks! Yes, we did an uPD7220 board on the N8VEM project. It
> generates VGA compatible 640x480 and 800x600 color displays. It can
> use modern LCDs and the board includes a VGA compatible RAMDAC for a
> lot of color control. The project works nicely after 2 or 3 rounds of
> prototypes. It is all documented on the N8VEM wiki in the uPD7220
> folder under ECB IO boards.
>
> I still have several PCBs left. They are ECB boards but can easily be
> interfaced to any Z80 type home brew computer system. Please take a
> look at the pictures as the boards work really well and generate a
> nice display. They are "period authentic" full color displays using
> modern hardware.
>
> Any and all uPD7220 enthusiasts welcome! Thanks and have a nice day!
>
> Andrew Lynch
I'll have a look, thanks.
TTFN,
Tarkin
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