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I thought it about time to lay out the format of a standard Oric tape header...

$16
$16
$16 (Minimum of three $16's)

$24 (Synchronisation byte)

$0
$0

$0(Basic) or $80(Assembler)

$0(No Autostart) or $80(Basic Autostart) or $C7(Assembly Autostart)

High Byte of the End address
Low Byte of the End Address

High Byte of the Start Address
Low Byte of the Start Address

$0

Filename(Up to 16 characters)

$0

Program Data


Note that i have used hexadecimal notation throughout

hello,

yes

thanks

I have ben reading some tap files with a hex editor I find that the header content is not consistence

I expected the data start stop addresses and file name addresses to be in the same place all the time

regards

john davis uk

As written the number of $16 is variable because it's a synchronization pattern, technically you could have many of them, it just happens that 3 is the minimum that still gives readable data.
The rest is consistent.

hello

I have download all of the theoric magazines and found this in issue #19

It explains the tape format

see attached

regards

john davis uk

hello

I have download all of the theoric magazines and found this in issue #19

It explains the tape format

see attached
regards

john davis uk

I've thrown this onto the wiki, which I think matches the exposition given above plus some detail on the actual waveform and a brief mention of the hardware/software implementation. Hopefully it's accurate but if not then, well, it's a wiki. So easy to fix.

In an old discussion about it, we establised that the Oric ROM actually needs four $16 at the beginning of the file. 1st one is used to synch the signal decoding, the 3 next to confirm it's the header synch sequence.
That's funny because for a long time I thought the Oric synchronised its reading speed according to the tape player speed, but actually no: it synchronises the byte decoding, passing bits to start at the right one to decode the next byte.

Also, I wonder if there are no specific values for commands like STORE.

I've updated the wiki page to say four rather than three but otherwise I think we're of an understanding: the Oric decides how quickly the tape is running, and whether encoding is slow or fast, just by inspective the waves as detected. Is that what we both think?

Thanks for the update!

Aha, sorry when I was talking about "speed" in my old (and wrong!) synchronisation understanding, I meant the tape player speed which can vary a little form one player to another! In my youth I thought the synch header was used by the Oric to adapt itself to a tape that was played 5% faster for instance - which is absolutely not what's happening

About fast or slow encoding/decoding speed, it's the human being that decides the decoding speed, by adding ",S" or not after CLOAD Thankfully by ear we can recognise a slow or fast recording!

Back in the days when I had a real Oric Atmos, I always thought that it would have been better if the tape header was always saved in SLOW format with a flag in the header to say whether the main program/data was FAST or SLOW format. That way when using CLOAD the ',S' parameter wouldn't be needed.