IEEE-488 adapter for 1541

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IEEE-488 adapter for 1541

Jeff_Birt

Saw this posted on they Lemon64 forum, thought it was an interesting project.

 

https://dl2dw.de/en/diy-projects/commodore/50-trimod-cbm-adapter

 

Jeff_Birt (Hey Birt!)

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Re: IEEE-488 adapter for 1541

Francesco Messineo
Hi Jeffrey!
I also started some years ago my own project for converting a 1451
into a 2031LP, of course with switchable kernel and maintaining both
ports. A daughterboard is quite an easy thing to add to the 6522.
However I realized that 1541 format isn't write-compatible with the
3040/4040, so at least for me it wouldn't allow me to share the same
disk (well, share in read only mode, yes) between my PETs.
Converting a 1541C is way easier anyway, you don't need a ROM adapter,
just a 27256 and a switch and you can re-use the 27128 socket on the
1541C motherboard.

Frank

On Sat, Apr 6, 2019 at 5:31 PM Jeffrey Birt <[hidden email]> wrote:

>
> Saw this posted on they Lemon64 forum, thought it was an interesting project.
>
>
>
> https://dl2dw.de/en/diy-projects/commodore/50-trimod-cbm-adapter
>
>
>
> Jeff_Birt (Hey Birt!)

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Re: IEEE-488 adapter for 1541

Jim Brain
In reply to this post by Jeff_Birt
On 4/6/2019 10:20 AM, Jeffrey Birt wrote:

Saw this posted on they Lemon64 forum, thought it was an interesting project.

 

https://dl2dw.de/en/diy-projects/commodore/50-trimod-cbm-adapter

 

Jeff_Birt (Hey Birt!)

Darn, I was working on the same thing, but had not gotten it finished :-)

Obviously, I think it's a cool idea.

Jim

-- 
Jim Brain
[hidden email] 
www.jbrain.com
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RE: IEEE-488 adapter for 1541

Jeff_Birt
In reply to this post by Francesco Messineo
Hi Frank,
Do you have any more information about converting the 1541C?

Jeff_Birt (Hey Birt!)

-----Original Message-----
From: Francesco Messineo <[hidden email]>
Sent: Saturday, April 6, 2019 10:37 AM
To: [hidden email]
Subject: Re: IEEE-488 adapter for 1541

Hi Jeffrey!
I also started some years ago my own project for converting a 1451 into a 2031LP, of course with switchable kernel and maintaining both ports. A daughterboard is quite an easy thing to add to the 6522.
However I realized that 1541 format isn't write-compatible with the 3040/4040, so at least for me it wouldn't allow me to share the same disk (well, share in read only mode, yes) between my PETs.
Converting a 1541C is way easier anyway, you don't need a ROM adapter, just a 27256 and a switch and you can re-use the 27128 socket on the 1541C motherboard.

Frank

On Sat, Apr 6, 2019 at 5:31 PM Jeffrey Birt <[hidden email]> wrote:

>
> Saw this posted on they Lemon64 forum, thought it was an interesting project.
>
>
>
> https://dl2dw.de/en/diy-projects/commodore/50-trimod-cbm-adapter
>
>
>
> Jeff_Birt (Hey Birt!)





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Re: IEEE-488 adapter for 1541

Francesco Messineo
Hi Jeffrey,
I've never went further than the schematic phase on my project, but
the only difference (for this particular case) between a 1541 and
1541C is that the -C has a single 16kbytes ROM instead of the 2 x
8kbytes ROMs of the old 1541. It can however run the same firmware as
all the memory mappings are the same. The original 1541C ROM has an
additional CS2 line tied to +5V on pin 27, so to install a dual
firmware, you can simply use a 27256 EPROM with pin 27 left outside
the socket and connect it  to any of the power rails via a 4k7
resistor, then connect a switch to the same pin that goes to the other
supply rail. So you can select either the lower 16K half or the upper
16K half of the 27256 (its pin 27 is A14). On one half you can burn
the original 1541C (or any other 1541's version) firmware and on the
other half, the complete 2031 firmware.
The daughterboard going into the 6522 socket is the same for all the
1541 versions.
It's just easier because you don't need an adapter to substitute the
original 2364 ROMs of the 1541. Also 1541C tend to be cheaper (the
same apply to the 1541-II, but this one has less space inside the
case) than the 1541 and often they have a mechanic with a track-0
sensor (that you enable by cutting JP3, but it needs the right
firmware to be effective, and also I've seen some 1541C without the
sensor installed) that it's really good to avoid the infamous track-0
sound when a formatting starts or in case of read errors.
As I said, I abandoned the conversion project because I'd rather have
a write compatible unit with the 3040 that I'm now sharing between my
PETs.

On Sat, Apr 6, 2019 at 7:25 PM Jeffrey Birt <[hidden email]> wrote:

>
> Hi Frank,
> Do you have any more information about converting the 1541C?
>
> Jeff_Birt (Hey Birt!)
>
> -----Original Message-----
> From: Francesco Messineo <[hidden email]>
> Sent: Saturday, April 6, 2019 10:37 AM
> To: [hidden email]
> Subject: Re: IEEE-488 adapter for 1541
>
> Hi Jeffrey!
> I also started some years ago my own project for converting a 1451 into a 2031LP, of course with switchable kernel and maintaining both ports. A daughterboard is quite an easy thing to add to the 6522.
> However I realized that 1541 format isn't write-compatible with the 3040/4040, so at least for me it wouldn't allow me to share the same disk (well, share in read only mode, yes) between my PETs.
> Converting a 1541C is way easier anyway, you don't need a ROM adapter, just a 27256 and a switch and you can re-use the 27128 socket on the 1541C motherboard.
>
> Frank
>
> On Sat, Apr 6, 2019 at 5:31 PM Jeffrey Birt <[hidden email]> wrote:
> >
> > Saw this posted on they Lemon64 forum, thought it was an interesting project.
> >
> >
> >
> > https://dl2dw.de/en/diy-projects/commodore/50-trimod-cbm-adapter
> >
> >
> >
> > Jeff_Birt (Hey Birt!)
>
>
>
>
>

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Re: IEEE-488 adapter for 1541

André Fachat


Am 6. April 2019 19:51:25 schrieb Francesco Messineo
<[hidden email]>:

>

>
>
> As I said, I abandoned the conversion project because I'd rather have
> a write compatible unit with the 3040 that I'm now sharing between my
> PETs.

The write difference is in the gap length between header and block IIRC and
this would be a simple one byte change I'd expect or maybe two if you add
the format routine.

So should be doable with a simple conversion.

Regards
André
>



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RE: IEEE-488 adapter for 1541

Jeff_Birt
In reply to this post by Francesco Messineo
Ah, OK. Somehow, I thought from your first message that the 6522 wasn’t need on the 1541-C and I did not see how that could work 😊

Thanks!

Jeff_Birt (Hey Birt!)

-----Original Message-----
From: Francesco Messineo <[hidden email]>
Sent: Saturday, April 6, 2019 12:48 PM
To: [hidden email]
Subject: Re: IEEE-488 adapter for 1541

Hi Jeffrey,
I've never went further than the schematic phase on my project, but the only difference (for this particular case) between a 1541 and 1541C is that the -C has a single 16kbytes ROM instead of the 2 x 8kbytes ROMs of the old 1541. It can however run the same firmware as all the memory mappings are the same. The original 1541C ROM has an additional CS2 line tied to +5V on pin 27, so to install a dual firmware, you can simply use a 27256 EPROM with pin 27 left outside the socket and connect it  to any of the power rails via a 4k7 resistor, then connect a switch to the same pin that goes to the other supply rail. So you can select either the lower 16K half or the upper 16K half of the 27256 (its pin 27 is A14). On one half you can burn the original 1541C (or any other 1541's version) firmware and on the other half, the complete 2031 firmware.
The daughterboard going into the 6522 socket is the same for all the
1541 versions.
It's just easier because you don't need an adapter to substitute the original 2364 ROMs of the 1541. Also 1541C tend to be cheaper (the same apply to the 1541-II, but this one has less space inside the
case) than the 1541 and often they have a mechanic with a track-0 sensor (that you enable by cutting JP3, but it needs the right firmware to be effective, and also I've seen some 1541C without the sensor installed) that it's really good to avoid the infamous track-0 sound when a formatting starts or in case of read errors.
As I said, I abandoned the conversion project because I'd rather have a write compatible unit with the 3040 that I'm now sharing between my PETs.




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Re: IEEE-488 adapter for 1541

Francesco Messineo
In reply to this post by André Fachat
On Sat, Apr 6, 2019 at 8:26 PM André Fachat <[hidden email]> wrote:

>
>
>
> Am 6. April 2019 19:51:25 schrieb Francesco Messineo
> <[hidden email]>:
>
> >
>
> >
> >
> > As I said, I abandoned the conversion project because I'd rather have
> > a write compatible unit with the 3040 that I'm now sharing between my
> > PETs.
>
> The write difference is in the gap length between header and block IIRC and
> this would be a simple one byte change I'd expect or maybe two if you add
> the format routine.

does the 2031 firmware make a write compatible format with the 4040?
If yes, why did commodore change the 1541 code?

Frank

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Re: IEEE-488 adapter for 1541

Spiro Trikaliotis
Hello,

* On Sat, Apr 06, 2019 at 11:05:21PM +0200 Francesco Messineo wrote:
 
> does the 2031 firmware make a write compatible format with the 4040?
> If yes, why did commodore change the 1541 code?

No, it is not. The 2031 and 1540 are not write-compatible, the early
1541 are not, but later 1541 (starting with 901229-03) are write
compatible with both 2031 and 4040:

http://cbm-hackers.2304266.n4.nabble.com/C64-IEEE-interface-tp4659295p4660079.html

http://www.softwolves.com/arkiv/cbm-hackers/11/11677.html
(have a look at the discussion of "GAP" being $08 or $09)

Regards,
Spiro.

--
Spiro R. Trikaliotis
http://www.trikaliotis.net/

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Re: IEEE-488 adapter for 1541

vossi
Like Spiro said, later 1541 are write compatible to cbm-drives.
But The 3040, 4040, 2031 HP have different heads than the 1541 has.

I had a 4040 connected to my MMF and wrote disks for it with my
1541@zoomfloppy.
But after some month I have problems to read the disks - I also tried the
2031HP - the same problems.
Both drives are perfectly adjusted and cleaned by me - incl. speed
adjustment.
Fresh good 1541-written disks work great, but with the time I get problems.
I also tried other 1541-drives to write disks - but still read problems...

But The disks I wrote in the 4040 itself are running perfectly.

I think the older cbm-drives have different write and or output power in the
analog part.

PS: Now I use only 8050 /sfd1001 disks in all my PET/cbms - and no problems
anymore.



-----
greets
Christian
--
Sent from: http://cbm-hackers.2304266.n4.nabble.com/

greets
Christian
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Re: IEEE-488 adapter for 1541

Francesco Messineo
In reply to this post by Spiro Trikaliotis
Hi Spiro,

On Sun, Apr 7, 2019 at 10:14 AM Spiro Trikaliotis
<[hidden email]> wrote:

>
> Hello,
>
> * On Sat, Apr 06, 2019 at 11:05:21PM +0200 Francesco Messineo wrote:
>
> > does the 2031 firmware make a write compatible format with the 4040?
> > If yes, why did commodore change the 1541 code?
>
> No, it is not. The 2031 and 1540 are not write-compatible, the early
> 1541 are not, but later 1541 (starting with 901229-03) are write
> compatible with both 2031 and 4040:
>
> http://cbm-hackers.2304266.n4.nabble.com/C64-IEEE-interface-tp4659295p4660079.html
>
> http://www.softwolves.com/arkiv/cbm-hackers/11/11677.html
> (have a look at the discussion of "GAP" being $08 or $09)

Yes, I've read again those threads, so my next question is: what
changes need to be made to the 2031 firmware to make it write
compatible with the 4040? Is there a single byte to change to have 10
bytes gap like the 4040 does?

Frank

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Re: IEEE-488 adapter for 1541

MiaM
In reply to this post by Francesco Messineo
Den Sat, 6 Apr 2019 17:37:27 +0200 skrev Francesco Messineo
<[hidden email]>:

> Hi Jeffrey!
> I also started some years ago my own project for converting a 1451
> into a 2031LP, of course with switchable kernel and maintaining both
> ports. A daughterboard is quite an easy thing to add to the 6522.
> However I realized that 1541 format isn't write-compatible with the
> 3040/4040, so at least for me it wouldn't allow me to share the same
> disk (well, share in read only mode, yes) between my PETs.
> Converting a 1541C is way easier anyway, you don't need a ROM adapter,
> just a 27256 and a switch and you can re-use the 27128 socket on the
> 1541C motherboard.

Isn't the 1541C like a 1541 but with a track 0 sensor and changed ROM
to use that sensor? My impression were that this still used two 8kbyte
ROMs.

IIRC the track 0 sensor interferes with the I/O ports required for the
IEEE-488 port. The linked description probably takes care of this, but
I'd advice to check what parts of the ROM does the track 0 check. If it
isn't in the same ROM as the IEEE/IEC code, then both ROMs needs to be
switched instead of only one of them.

While 1541-II is the new style case drive which indeed uses one 16kbyte
27128.

--
(\_/) Copy the bunny to your mails to help
(O.o) him achieve world domination.
(> <) Come join the dark side.
/_|_\ We have cookies.

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Re: IEEE-488 adapter for 1541

Francesco Messineo
On Sun, Apr 7, 2019 at 9:56 PM Mia Magnusson <[hidden email]> wrote:
>
> Den Sat, 6 Apr 2019 17:37:27 +0200 skrev Francesco Messineo
> <[hidden email]>:

>
> Isn't the 1541C like a 1541 but with a track 0 sensor and changed ROM
> to use that sensor? My impression were that this still used two 8kbyte
> ROMs.

Nope, I have all the versions and often repair them for other people.
the only drives that have 2 x 8K ROMs are the long board and short board 1541.
Schematic is available on zimmers.net if you like to check yourself.
It's called 1541B.

> IIRC the track 0 sensor interferes with the I/O ports required for the
> IEEE-488 port. The linked description probably takes care of this, but
> I'd advice to check what parts of the ROM does the track 0 check. If it
> isn't in the same ROM as the IEEE/IEC code, then both ROMs needs to be
> switched instead of only one of them.

Not all the 1541C have a track-0 sensor, and anyway it's connected to
PA0 of th 6522 that is a data line for IEEE-488, but since you need to
add switches for port-B pins that have other functions in the IEC
drive, you just add another logic (or analog, like CBM engineers would
have done) on PA0 pin.


>
> While 1541-II is the new style case drive which indeed uses one 16kbyte
> 27128.
Yes, of course those use a single ROM too.

Frank IZ8DWF

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Re: IEEE-488 adapter for 1541

Francesco Messineo
On Sun, Apr 7, 2019 at 10:21 PM Francesco Messineo
<[hidden email]> wrote:

>
> On Sun, Apr 7, 2019 at 9:56 PM Mia Magnusson <[hidden email]> wrote:
> >
> > Den Sat, 6 Apr 2019 17:37:27 +0200 skrev Francesco Messineo
>
> Not all the 1541C have a track-0 sensor, and anyway it's connected to
> PA0 of th 6522 that is a data line for IEEE-488, but since you need to
> add switches for port-B pins that have other functions in the IEC
> drive, you just add another logic (or analog, like CBM engineers would
> have done) on PA0 pin.

I meant logic or analog switch
Frank IZ8DWF

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Re: IEEE-488 adapter for 1541

Spiro Trikaliotis
In reply to this post by Francesco Messineo
Hello Francesco,

* On Sun, Apr 07, 2019 at 11:13:47AM +0200 Francesco Messineo wrote:
 
> Yes, I've read again those threads, so my next question is: what
> changes need to be made to the 2031 firmware to make it write
> compatible with the 4040? Is there a single byte to change to have 10
> bytes gap like the 4040 does?

You have to change the INTRA_SECTOR_GAP:

http://cbmrom.trikaliotis.net/listings/2031-01.lst

You can find it at $F5DB (F5DA: ldx #INTRA_SECTOR_GAP) and $FD1F (FD1E:
ldx #INTRA_SECTOR_GAP).

Other than that, you also have to adjust the ROM checksum (at $FF35 in
the 2031 ROM), or disable the ROM selftest.

Regards,
Spiro.

--
Spiro R. Trikaliotis
http://www.trikaliotis.net/

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Re: IEEE-488 adapter for 1541

Francesco Messineo
On Sun, Apr 7, 2019 at 11:03 PM Spiro Trikaliotis
<[hidden email]> wrote:

>
> Hello Francesco,
>
> * On Sun, Apr 07, 2019 at 11:13:47AM +0200 Francesco Messineo wrote:
>
> > Yes, I've read again those threads, so my next question is: what
> > changes need to be made to the 2031 firmware to make it write
> > compatible with the 4040? Is there a single byte to change to have 10
> > bytes gap like the 4040 does?
>
> You have to change the INTRA_SECTOR_GAP:
>
> http://cbmrom.trikaliotis.net/listings/2031-01.lst
>
> You can find it at $F5DB (F5DA: ldx #INTRA_SECTOR_GAP) and $FD1F (FD1E:
> ldx #INTRA_SECTOR_GAP).
>
> Other than that, you also have to adjust the ROM checksum (at $FF35 in
> the 2031 ROM), or disable the ROM selftest.

Thanks a lot! I might resume the project at this point. It would be
good to have a small drive for the PETs.
(and the 1001 is way too pricey).

Regards.
Frank
>
> Regards,
> Spiro.
>
> --
> Spiro R. Trikaliotis
> http://www.trikaliotis.net/
>