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A kinda long shot...

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Ian Rogers

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Has any of our members experience reading and writing to a magnetic tape...

I want to interface a specific magnetic tape drive to a PC... I have looked aimlessly through countless pages, but not really sure what I'm looking for...

The tape is a microdrive used by Dr Sinclair way back when these were the dogs dodah's... I know tons already.. speed bits per cm.. data polarisation etc.. But I don't know, and seem to not be able to find out, the data format... I am assuming similar to cassette tape drives...

Dr Sinclair used ULA chips to do all the mundane stuff, so the old "black box" theory... The device in question is on my new...LOL new!! QL... I want to make a transfer utility....
 

Ian Rogers

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Cheers bob.... Funny, I have that book... I never realised the content about the microdrive.. I still need some more info though...

I'll do a thorough read and see if I can get it working with an older PC...
 

Tony Stewart

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I had a regular cassette recorder with a 9600 Baud realtime port for transferrng MC6800 Code onto our custom motherboard 1978. I understand this is an endless loop supporting 115kbps.

Having done 10 yrs in Mag recording industry, I would expect internal tape format is MFM (RLL 1,2)... but dont know what this unit interface protocol actually used.

... Around same time I had a musician friend in mid-80's with a SONY VCR Betamax with a 1Mbps interface for his digital studio recordings.

This design suffered from tape tension control and very unreliable. The HP9825 I had in '77 had a high speed mini cartridge and very reliable.
 
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Ian Rogers

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Having done 10 yrs in Mag recording industry, I would expect internal tape format is MFM (RLL 1,2)... but dont know this user interface protocol.
I would have liked it to be so.... I have used MFM and RLL back on the x86.. But alass..... This is a continual tape and the whole 5 meters is read every access.. Each header ( leader ) and each datablock is divided by a space...

The book, as shown by Bob, Shows me the preamble, header and datablocks... I can fathom the preamble... 10 zero's and two full bytes, but after the header there is a "gap" this is 3.75ms, but of what?? If zero is polarized and one is not.. What would "gap" read.... I'm going to have to get out my old analogue storage scope and do a read, a write, and an erase so I can see what "gap" actually is... The reason is after the gap there is twelve more preamble bytes... So where does the "gap" end and the preamble start.
 

Ian Rogers

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Got that book as well... Incidentally that is the Spectrum rom.... The code is in the shadow rom in interface 1

I have that as well....

However!! I found the snippet that seems to be missing..

The reason it was eluding me was the preamble and the gaps... BUT!!! they aren't part of the code...So it wasn't documented... The snippet I found was the last piece of the jigsaw... I should be able to make the interface work now..

The only thing now is.. The QL and the spectrum run the microdrives at slightly different speeds...
 
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