6809 in a C64

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6809 in a C64

Jim Brain

Ruud:

In reference to this old posting:

http://www.softwolves.com/arkiv/cbm-hackers/13/13116.html

I thought I'd note that I designed a C64 cartridge containing a MC6809 and some RAM.  I know it's not exactly the same as your idea, but it is easier to prototype.

https://www.facebook.com/go4retro/photos/a.386509271508869.1073741826.386509238175539/984731561686634/?type=3&theater

The initial goal is to multiplex the two CPUs, allowing the 6809 to access some shared RAM on the low PHI2 portion of the cycle, and 64 access on the high portion.  Then, I'll try to speed up the 6809 to 4MHz and see if I can keep the shared memory in place.

Possibly later, I'll see if I can have the 6809 take over the bus like SuperCPU and Chameleon64, but I suspect I have to learn quite a bit more about the system bus.

Jim


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Jim Brain
[hidden email] 
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RE: 6809 in a C64

Baltissen, GJPAA (Ruud)

Hallo Jim,

 

Looks very promising!

 

Met vriendelijke groet / With kind regards, Ruud Baltissen

 

www.Baltissen.org

 

 

 

From: Jim Brain <[hidden email]>
Sent: woensdag 23 mei 2018 08:10
To: [hidden email]
Subject: 6809 in a C64

 

Ruud:

In reference to this old posting:

http://www.softwolves.com/arkiv/cbm-hackers/13/13116.html

I thought I'd note that I designed a C64 cartridge containing a MC6809 and some RAM.  I know it's not exactly the same as your idea, but it is easier to prototype.

https://www.facebook.com/go4retro/photos/a.386509271508869.1073741826.386509238175539/984731561686634/?type=3&theater

The initial goal is to multiplex the two CPUs, allowing the 6809 to access some shared RAM on the low PHI2 portion of the cycle, and 64 access on the high portion.  Then, I'll try to speed up the 6809 to 4MHz and see if I can keep the shared memory in place.

Possibly later, I'll see if I can have the 6809 take over the bus like SuperCPU and Chameleon64, but I suspect I have to learn quite a bit more about the system bus.

Jim



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Re: 6809 in a C64

Steve Gray
In reply to this post by Jim Brain
Very cool! FYI, the Commodore 64 BTX cartridges also contain a 6809, but i haven't seen schematics for them anywhere. They also have their own video chip. Other than that, there's really not much info out there about them.

Steve



From: Jim Brain <[hidden email]>
To: [hidden email]
Sent: Wednesday, May 23, 2018 2:09 AM
Subject: 6809 in a C64

Ruud:
In reference to this old posting:
I thought I'd note that I designed a C64 cartridge containing a MC6809 and some RAM.  I know it's not exactly the same as your idea, but it is easier to prototype.
The initial goal is to multiplex the two CPUs, allowing the 6809 to access some shared RAM on the low PHI2 portion of the cycle, and 64 access on the high portion.  Then, I'll try to speed up the 6809 to 4MHz and see if I can keep the shared memory in place.
Possibly later, I'll see if I can have the 6809 take over the bus like SuperCPU and Chameleon64, but I suspect I have to learn quite a bit more about the system bus.
Jim

-- 
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[hidden email] 
www.jbrain.com


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Re: 6809 in a C64

Konrad B
"BTX Decoder Modul II", the one in REU-like case, has the 6803 MPU and
is interfaced to the "main CPU" with the 68HC34 dual port RAM.

Regards,
Konrad

2018-05-23 14:35 GMT+02:00 Steve Gray <[hidden email]>:

> Very cool! FYI, the Commodore 64 BTX cartridges also contain a 6809, but i
> haven't seen schematics for them anywhere. They also have their own video
> chip. Other than that, there's really not much info out there about them.
>
> Steve
>
>
> ________________________________
> From: Jim Brain <[hidden email]>
> To: [hidden email]
> Sent: Wednesday, May 23, 2018 2:09 AM
> Subject: 6809 in a C64
>
> Ruud:
> In reference to this old posting:
> http://www.softwolves.com/arkiv/cbm-hackers/13/13116.html
> I thought I'd note that I designed a C64 cartridge containing a MC6809 and
> some RAM.  I know it's not exactly the same as your idea, but it is easier
> to prototype.
> https://www.facebook.com/go4retro/photos/a.386509271508869.1073741826.386509238175539/984731561686634/?type=3&theater
> The initial goal is to multiplex the two CPUs, allowing the 6809 to access
> some shared RAM on the low PHI2 portion of the cycle, and 64 access on the
> high portion.  Then, I'll try to speed up the 6809 to 4MHz and see if I can
> keep the shared memory in place.
> Possibly later, I'll see if I can have the 6809 take over the bus like
> SuperCPU and Chameleon64, but I suspect I have to learn quite a bit more
> about the system bus.
> Jim
>
> --
> Jim Brain
> [hidden email]
> www.jbrain.com
>
>
>

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Re: 6809 in a C64

Michael Brant
In reply to this post by Jim Brain
Jim, I almost got confused and thought I was reading the coco mailing list.  Lol this is quite interesting. 

On Wed, May 23, 2018, 2:11 AM Jim Brain <[hidden email]> wrote:

Ruud:

In reference to this old posting:

http://www.softwolves.com/arkiv/cbm-hackers/13/13116.html

I thought I'd note that I designed a C64 cartridge containing a MC6809 and some RAM.  I know it's not exactly the same as your idea, but it is easier to prototype.

https://www.facebook.com/go4retro/photos/a.386509271508869.1073741826.386509238175539/984731561686634/?type=3&theater

The initial goal is to multiplex the two CPUs, allowing the 6809 to access some shared RAM on the low PHI2 portion of the cycle, and 64 access on the high portion.  Then, I'll try to speed up the 6809 to 4MHz and see if I can keep the shared memory in place.

Possibly later, I'll see if I can have the 6809 take over the bus like SuperCPU and Chameleon64, but I suspect I have to learn quite a bit more about the system bus.

Jim


-- 
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[hidden email] 
www.jbrain.com
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Re: 6809 in a C64

MiaM
In reply to this post by Konrad B
Den Wed, 23 May 2018 15:22:44 +0200 skrev Konrad B
<[hidden email]>:
> 2018-05-23 14:35 GMT+02:00 Steve Gray <[hidden email]>:
> > Very cool! FYI, the Commodore 64 BTX cartridges also contain a
> > 6809, but i haven't seen schematics for them anywhere. They also
> > have their own video chip. Other than that, there's really not much
> > info out there about them.

> "BTX Decoder Modul II", the one in REU-like case, has the 6803 MPU and
> is interfaced to the "main CPU" with the 68HC34 dual port RAM.

Why were it made that way?

Did the German BTX have some fancy features that the British
(Viewdata?) and Swedish Teledata never had?

Handic/Datatronic, the Commodore importer in Sweden up to 85, made a
software-only solution for the terminal emulation. The cart only
contained an eprom, easily pirateable (or so I've heard...), and the
hardware were an AM7910/7911 (can't remember which) on a board in a box
that plugged in to the user port. Four "radio buttons" push buttons to
select 75/1200 with and without some kind of equalization, and 300/300
originate and answer (according to the European CCITT standard,
although you surely could rewire the modem to use the Bell standard for
300 baud if you wanted to dial cross the ocean). There were also two
momentary push buttons labeled data and telephone (but in Swedish), and
a LED. You dialed using your ordinary phone and when you heard the tone
of the modem in the other end, you pushed and held "data" for a while,
and hoped that the LED would still be lit when you released the button.
As long as the modem IC detected the other ends carrier the LED would
keep lighting and and the modem would be connected. The C64 provided
power to the modem and the phone wire were soldered onto the board
directly.

Anyways the "TeleData 64" cartridge for Videotex emulation seemed to
emulate everything you wanted.

Not sure how it was done though. Maybe they used hires mode to be able
to freely select foreground and background colors? With 1200 baud
receiving data rate I guess that the 6510 had enough time to both
produce text in hires mode and receive data via the usual user port
RS232 bit bang method. (Sending must have been trivial as it was 75
baud).

With 1200 baud you receive one bit every 13th scan lines, and with 75
baud you send a bit each 208th scan line. That equals to one byte sent
every 6-7th frame and one byte recieved every 130th scan line, which
equals to about 2.4 bytes per frame. There should be plenty of time to
do all processing although you'd probably need a (ring) buffer to not
drop characters after a screen clear or scroll operation.

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Re: 6809 in a C64

Groepaz
Am Mittwoch, 23. Mai 2018, 15:50:03 CEST schrieb Mia Magnusson:

> Den Wed, 23 May 2018 15:22:44 +0200 skrev Konrad B
>
> <[hidden email]>:
> > 2018-05-23 14:35 GMT+02:00 Steve Gray <[hidden email]>:
> > > Very cool! FYI, the Commodore 64 BTX cartridges also contain a
> > > 6809, but i haven't seen schematics for them anywhere. They also
> > > have their own video chip. Other than that, there's really not much
> > > info out there about them.
> >
> > "BTX Decoder Modul II", the one in REU-like case, has the 6803 MPU and
> > is interfaced to the "main CPU" with the 68HC34 dual port RAM.
>
> Why were it made that way?
>
> Did the German BTX have some fancy features that the British
> (Viewdata?) and Swedish Teledata never had?

IIRC it originates from typical german regulations - ie "software" decoders
were illegal at the beginning, only certified devices were allowed to be used
with BTX.

--

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http://vice-emu.sourceforge.net  http://magicdisk.untergrund.net

If you mean vaxx stuff or chemtrails stuff, etc.etc. I can tell you it's real
- like it or not. EOD.
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Re: 6809 in a C64

Anders Carlsson
In reply to this post by MiaM
Mia Magnusson wrote:

> Maybe they used hires mode to be able to freely select foreground and
> background colors?
>
Bingo!

I just downloaded Teledata.CRT and remembered that the title screen has
double height text which of course requires either a full set of custom
characters or working in hires mode. According to a register dump in
VICE, $D011 is set to $3B = hires mode and $D018 = $29. The latter
register appears to be set all the time, which kind of suggests there
are two buffers of hires data so the program can switch between those.
Probably that it loads and generates a videotex page in the buffer not
currently displayed and switches to that one when it is done.

Whether generating a hires screen for every page loaded had been faster
with a 6809 in the cartridge to offload the 6510 inside the computer is
beyond my knowledge, but I understand that the BTX cartridges might use
the 680x chips more due to the (existing?) hardware decoding solution
was based on those CPUs than for speed purposes.

Best regards

Anders Carlsson



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Re: 6809 in a C64

J. Alexander Jacocks
Jim,

This looks to be an excellent beginning.  I'm very enthusiastic about the options for using the 6809, as I have always been impressed with the overall execution efficiency of that CPU.

Is there any interest for the c128 use of this cart?  The 80 column RGB modes would be a significant plus for OS9.

- Alex

On Wed, May 23, 2018 at 10:28 AM, Anders Carlsson <[hidden email]> wrote:
Mia Magnusson wrote:

Maybe they used hires mode to be able to freely select foreground and background colors?

Bingo!

I just downloaded Teledata.CRT and remembered that the title screen has double height text which of course requires either a full set of custom characters or working in hires mode. According to a register dump in VICE, $D011 is set to $3B = hires mode and $D018 = $29. The latter register appears to be set all the time, which kind of suggests there are two buffers of hires data so the program can switch between those. Probably that it loads and generates a videotex page in the buffer not currently displayed and switches to that one when it is done.

Whether generating a hires screen for every page loaded had been faster with a 6809 in the cartridge to offload the 6510 inside the computer is beyond my knowledge, but I understand that the BTX cartridges might use the 680x chips more due to the (existing?) hardware decoding solution was based on those CPUs than for speed purposes.

Best regards

Anders Carlsson




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Re: 6809 in a C64

MiaM
In reply to this post by Groepaz
Den Wed, 23 May 2018 16:00:18 +0200 skrev [hidden email]:

> Am Mittwoch, 23. Mai 2018, 15:50:03 CEST schrieb Mia Magnusson:
> > Den Wed, 23 May 2018 15:22:44 +0200 skrev Konrad B
> >
> > <[hidden email]>:
> > > 2018-05-23 14:35 GMT+02:00 Steve Gray <[hidden email]>:
> > > > Very cool! FYI, the Commodore 64 BTX cartridges also contain a
> > > > 6809, but i haven't seen schematics for them anywhere. They also
> > > > have their own video chip. Other than that, there's really not
> > > > much info out there about them.
> > >
> > > "BTX Decoder Modul II", the one in REU-like case, has the 6803
> > > MPU and is interfaced to the "main CPU" with the 68HC34 dual port
> > > RAM.
> >
> > Why were it made that way?
> >
> > Did the German BTX have some fancy features that the British
> > (Viewdata?) and Swedish Teledata never had?
>
> IIRC it originates from typical german regulations - ie "software"
> decoders were illegal at the beginning, only certified devices were
> allowed to be used with BTX.

We had that kind of regulations too, but sometime in perhaps 83-84 third
party vendors could get their modems approved, so Handic/Datatronic got
their modem for C64 approved. I guess that this was partially due to
the telco wanted people to get on to their "Datavision" service.

Afaik there were no special regulation on actual usage of the
Datavision (Swedish national monopoly telcos BTX/Viewdata/Prestel
service), only that the modem had to be approved for connecting to the
public telephone network. Btw for some reason the Swedish post (totally
separate from the telco right from the start) had their own Prestel
service. I don't know why (, and I also don't know why they started a
web site in the 90's as it didn't generate any revenue for them, while
the telco operated website generated dialup traffic)...

--
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Re: 6809 in a C64

MiaM
In reply to this post by Anders Carlsson
Den Wed, 23 May 2018 16:28:20 +0200 skrev Anders Carlsson
<[hidden email]>:

> Mia Magnusson wrote:
>
> > Maybe they used hires mode to be able to freely select foreground
> > and background colors?
> >
> Bingo!
>
> I just downloaded Teledata.CRT and remembered that the title screen
> has double height text which of course requires either a full set of
> custom characters or working in hires mode.

Oh yes, I forgot about that. So both double height chars and free
choice of foreground/background combinations are the reasons for hires
mode.

Btw did you somehow see if it would produce the Swedish national chars
ÅÄÖ even without those chars in charrom?

> According to a register dump in VICE, $D011 is set to $3B = hires
> mode and $D018 = $29. The latter register appears to be set all the
> time, which kind of suggests there are two buffers of hires data so
> the program can switch between those. Probably that it loads and
> generates a videotex page in the buffer not currently displayed and
> switches to that one when it is done.

It would be almost trivial to test how it works with real modem data.
As you dial up with your phone and not your computer, it would just
recieve data using 1200bps and display it without any working transmit
connection. Thus you could just hook up an RS232 interface and a null
modem to any other computer and just send Prestel coded data in 1200
baud and just ignoring the 75 baud back channel.

A qualified guess is that they might have used two hires screens to
make scrolling less jerky, and also to make a screen clear to appear
instant.

Or I might remember things badly, were there even scrolling on Prestel
or did you just have everything in one page?

Anyway afaik Teledata did support downloading a few pages and keeping
them in memory, maybe running them as a slide show, so they probably
used two hires screens to be able to flip screens without jerkyness.
When in online mode they might have used two screens just to have an
already cleared screen to flip to as soon as a clear screen command is
received, and then slowly clearing the other screen when there are
cycles left over.

(Never had any manual for the software back in the days, and those
features aren't intuitive so I never figured them out IIRC).

> Whether generating a hires screen for every page loaded had been
> faster with a 6809 in the cartridge to offload the 6510 inside the
> computer is beyond my knowledge, but I understand that the BTX
> cartridges might use the 680x chips more due to the (existing?)
> hardware decoding solution was based on those CPUs than for speed
> purposes.

But the 68xx and 65xx buses are rather similar, so at least most
peripherals can be used with either CPU. Maybe that knowledge weren't
passed along to such extent back in the days?

Or maybe there were just example code written for 68xx which they used
for most computers?

For example I've read that there were a peripheral for Atari which
contained a modem or serial interface, some video generation and some
CPU, for Prestel. Expensive. Afaik there were also something similar
available for Spectravideo.

Even though the C64 were in the top of the price range on home
computers back in the days, it must have been one of the cheapest
solutions for Prestel.

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Re: 6809 in a C64

Jim Brain
In reply to this post by J. Alexander Jacocks
On 5/23/2018 10:31 AM, J. Alexander Jacocks wrote:
> Jim,
>
> This looks to be an excellent beginning.  I'm very enthusiastic about
> the options for using the 6809, as I have always been impressed with
> the overall execution efficiency of that CPU.
>
> Is there any interest for the c128 use of this cart?  The 80 column
> RGB modes would be a significant plus for OS9.
As I am currently implementing the cart, there is no C64-specific issues
with it.  It'll act like a dual processor machine with shared memory. 
Thus, by writing the correct drivers, one can use any facility of the
C128, including REUs and such.  The 8502 of the C128 (or the Z80, I
guess) would need to help move data to/from the 6809 cart.

Jim


smf
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Re: 6809 in a C64

smf
On 23/05/2018 18:31, Jim Brain wrote:
> The 8502 of the C128 (or the Z80, I guess) would need to help move
> data to/from the 6809 cart.

8502 probably, iirc the z80 can't read the capslock key & it has to ask
the 8502 to help.

Unless you can fix the z80 speed problems on the c128, even with vic
turned off the z80 doesn't get all cycles for some reason.



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Re: 6809 in a C64

MiaM
Den Wed, 23 May 2018 19:46:51 +0100 skrev smf <[hidden email]>:
> On 23/05/2018 18:31, Jim Brain wrote:
> > The 8502 of the C128 (or the Z80, I guess) would need to help move
> > data to/from the 6809 cart.
>
> 8502 probably, iirc the z80 can't read the capslock key & it has to
> ask the 8502 to help.
>
> Unless you can fix the z80 speed problems on the c128, even with vic
> turned off the z80 doesn't get all cycles for some reason.

But it has LDIR for fast transfers.

I think we have had this discussion before but unless the Z80 is
severely crippled LDIR should be faster than memory copy using the 8502.

--
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RE: 6809 in a C64

Baltissen, GJPAA (Ruud)
In reply to this post by J. Alexander Jacocks

Hallo Alex,

 

 

> Is there any interest for the c128 use of this cart?  The 80 column RGB modes would be a significant plus for OS9.

 

Good idea!

 

Them now a very wild shot in the dark: what about replacing the Z80 with the 6809 in some way? Again, a very wild shot because I haven't looked at the schematics yet. Just the thought occurred.

 

 

Met vriendelijke groet / With kind regards, Ruud Baltissen

 

www.Baltissen.org

 

 

 

 



De informatie in dit e-mailbericht is vertrouwelijk en uitsluitend bestemd voor de
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The information contained in this e-mail is confidential and may be privileged.
It may be read, copied and used only by the intended recipient.
If you have received it in error, please contact the sender immediately by
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Re: 6809 in a C64

Jim Brain
On 5/24/2018 12:41 AM, Baltissen, GJPAA (Ruud) wrote:

Hallo Alex,

 

 

> Is there any interest for the c128 use of this cart?  The 80 column RGB modes would be a significant plus for OS9.

 

Good idea!

 

Them now a very wild shot in the dark: what about replacing the Z80 with the 6809 in some way? Again, a very wild shot because I haven't looked at the schematics yet. Just the thought occurred.

I know we're all doing stuff because we can, but why pull a perfectly good Z80 out of the C128 when one can hang the 6809 off the cart port?

Jim

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RE: 6809 in a C64

Baltissen, GJPAA (Ruud)
Hallo Jim,

> but why pull a perfectly good Z80 out of the C128 when one can hang the 6809 off the cart port?

I rather prefer to have a 6809 on board than the Z80 but my main reason: it would free the expansion port so I will be able to use other cartridges.


Met vriendelijke groet / With kind regards, Ruud Baltissen

www.Baltissen.org




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The information contained in this e-mail is confidential and may be privileged.
It may be read, copied and used only by the intended recipient.
If you have received it in error, please contact the sender immediately by
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Re: 6809 in a C64

Jim Brain
On 5/24/2018 1:19 AM, Baltissen, GJPAA (Ruud) wrote:
> Hallo Jim,
>
>> but why pull a perfectly good Z80 out of the C128 when one can hang the 6809 off the cart port?
> I rather prefer to have a 6809 on board than the Z80 but my main reason: it would free the expansion port so I will be able to use other cartridges.
I think it's going to be tough to pull the Z80.  Bil Herd notes in his
stories that the C128 bootup relies on the Z80 pulling startup vectors
from low memory to handle carts like Magic Voice that play with the
control signals when 6502 vectors are pulled.

Ruud, I need to send you a cartridge expander.  :-)

Jim


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Re: 6809 in a C64

Anders Carlsson
In reply to this post by MiaM
Mia Magnusson wrote:

> Btw did you somehow see if it would produce the Swedish national chars
> ÅÄÖ even without those chars in charrom?

Yes, it displays the "Ö" in "V.G. ring önskad teledata-bas" when
emulated in VICE on an international C64.

> Or I might remember things badly, were there even scrolling on Prestel
> or did you just have everything in one page?

I can't tell for sure, but I doubt those pages scroll in either
direction. Slideshows yes, as you mentioned. A closer look at the code
would be in order if anyone is interested how it really works, but it
doesn't really fit in this topic, which was brought up by the fact the
BTX cartridges do have a co-pro while other Videotex oriented solutions
don't.

Best regards

Anders Carlsson



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Re: 6809 in a C64

smf
On 24/05/2018 13:48, Anders Carlsson wrote:
Or I might remember things badly, were there even scrolling on Prestel or did you just have everything in one page?

I can't tell for sure, but I doubt those pages scroll in either direction.

Prestel didn't scroll, but BTX wasn't exactly Prestel

https://en.wikipedia.org/wiki/CEPT_Recommendation_T/CD_06-01

https://en.wikipedia.org/wiki/Videotex#Standards

Meanwhile, the European national Postal Telephone and Telegraph (PTT) agencies were also increasingly interested in videotex, and had convened discussions in European Conference of Postal and Telecommunications Administrations (CEPT) to co-ordinate developments, which had been diverging along national lines. As well as the British and French standards, the Swedes had proposed extending the British Prestel standard with a new set of smoother mosaic graphics characters; while the specification for the proposed German Bildschirmtext (BTX) system, developed under contract by IBM Germany for Deutsche Bundespost, was growing increasingly baroque. Originally conceived to follow the UK Prestel system, it had accreted elements from all the other European standards and more. This became the basis for setting out the CEPT recommendation T/CD 06-01,[5][6] also proposed in May 1981. However, due to national pressure, CEPT stopped short of fixing a single standard, and instead recognised four "profiles": CEPT1, corresponding to the German BTX; CEPT 2, the French Minitel; CEPT 3, the British Prestel; and CEPT 4, the Swedish Prestel Plus. National videotex services were encouraged to follow one of the existing four basic profiles; or if they extended them, to do so in ways compatible with a "harmonised enhanced" specification. There was talk of upgrading Prestel to the full CEPT standard "within a couple of years". But in the event, it never happened. The German BTX eventually established CEPT1; the French Minitel continued with CEPT2, which was ready to roll out; and the British stayed with CEPT3, by now too established to break compatibility. The other countries of Europe adopted a patchwork of the different profiles.[7]

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