schematics for floppy disk interfaces

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Pr0f
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Re: schematics for floppy disk interfaces

Post by Pr0f »

Derek_Stewart wrote:Hi,

I had a look at the QEP III manual, which is a little lacking in a lot of places, but the Options Sub Menu indicate a Jumble option to jumble the data or address line.

The manual should of really describe the jumble function.
The jumble function allows any data line to be swapped for any other data line on the EPROM, and/or any address line to be swapped for another on the EPROM - as Dave said, this is to make it easier to route tracks on a pcb, since basically it doesn't actually really matter if D0 or D7 are swapped on the EPROM - as long as the data is correct when it's read on the databus. To make an image of the ROM you need to use SBYTES for the address the ROM is located at.


Silvester
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Re: schematics for floppy disk interfaces

Post by Silvester »

Pr0f wrote:To make an image of the ROM you need to use SBYTES for the address the ROM is located at.
To create a true binary representation use SBYTES (ie. see what the CPU actually reads). But to produce an EPROM image suitable for original PCB you need to either read EPROM directly or, knowing the 'jumble', use a BASIC program such as I did for QEP (see http://www.dilwyn.me.uk/qlrom/qep3v108.zip).


David
Derek_Stewart
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Re: schematics for floppy disk interfaces

Post by Derek_Stewart »

Hi,

If I follow the convert_bas to un-jumble the QEP3 ROM, the eprom data and address lines connection to the QL bus must be determined to produce the un-jumble sequence.


Regards,

Derek
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Pr0f
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Re: schematics for floppy disk interfaces

Post by Pr0f »

Derek_Stewart wrote:Hi,

If I follow the convert_bas to un-jumble the QEP3 ROM, the eprom data and address lines connection to the QL bus must be determined to produce the un-jumble sequence.
That could be done, as the QL expansion bus is well known, and the eproms have standard jedec pinouts - so data and address lines are also well known - it's just a 15 minute beep session with a multimeter :-)


Silvester
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Re: schematics for floppy disk interfaces

Post by Silvester »

Dave wrote:Look at the first four bytes and bit re-order them to get the correct ROM identifier, and that will be true for the whole ROM.
Ah, but not if the address lines have also been jumbled. The scrambled ROM identifier could be buried anywhere in the scrambled address range.

Though I guess it could be an interesting programming task to try to unravel it in BASIC.
Pr0f wrote: it's just a 15 minute beep session with a multimeter :-)
Sounds much easier :-)

(Thankfully Ian Burkinshaw did all the hard work in his excellent service manual for QEP3. In which both data and address lines have been jumbled :o ).


David
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BSJR
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Re: schematics for floppy disk interfaces

Post by BSJR »

aalea wrote:BSJR: there are any posibility to get a .img file of the utilities disk?
I hope this will do as well. Copied and zipped from the original "Utilities v3.0" disc.
QDisc3.zip
(10.12 KiB) Downloaded 134 times
BSJR


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aalea
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Re: schematics for floppy disk interfaces

Post by aalea »

BSJR wrote:
aalea wrote:BSJR: there are any posibility to get a .img file of the utilities disk?
I hope this will do as well. Copied and zipped from the original "Utilities v3.0" disc.
QDisc3.zip
BSJR
Thank You so much, this app are very intersting and usefull, I upload a img of the disk, in case somebody want to use it with a gotek drive emulator.
Attachments
Qdisk3_utils.zip
(147.2 KiB) Downloaded 111 times


nikosdoykas
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Re: schematics for floppy disk interfaces

Post by nikosdoykas »

so you can read witha programmer the 1.19 rom of your qdisk???
thanks for the disk...


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aalea
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Re: schematics for floppy disk interfaces

Post by aalea »

I think there are a name confusion.
BSJR, that provide the zip with the programs, have a 1.13 version.
I, that provide the disk, have the 1.16 clone, you should know, it's a blue PCB ;-)
Derek_Stewart is the one that publish pictures of the version 1.19.

I already started to reverse engineering of this PCB, I have all the Copper side and about 80% of the component side, I use kicad, not eagle, but i got enought information to say that the encription of the ROM is related to the Address lines, Data line are not swapped, but several Axx are.

So next is for Derek:
To advance it will be very useful not only the content of the rom directly from the chip, but also to obtain it from the QL, to be able to compare and verify that the Axx swap lines are correct.

It will also be very helpful if I can get a detailed picture, for example one that doesn't have the chips in the sockets, or other details that are not clear in the picture, and if you can do a basic check with an electrical (continuity) tester, we can share details of what I need privately if you don't want to dirty the threat.


Derek_Stewart
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Re: schematics for floppy disk interfaces

Post by Derek_Stewart »

Hi,

I will see what I can do with regards to the photograph.

I have copied the jumbled rom code to a file, I will determine the correct unjumble sequence of address and data lines and decode the Rom, I will save the QL Rom slot where the Rom is located, for comparison.

The Rom is v1.18


Regards,

Derek
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