Re: GCR specification - where?

["Dr. Wolfgang Otrebski" <wolfgang.otrebski@siemens.at>]

Matthew T. Russotto wrote:
<snip> 
 
> Sure they are.  Just count cycles :-).  Though somewhere in the dusty
> attic of my head I remember that it takes 32 cycles to write a disk
> nibble and 40 seconds to write a self-sync nibble.  So first you write
> a few self-syncs, then every 32 cycles you need to load the data latch
> with a new value until you're done writing nibbles.  Then I think you
> write some more self-syncs, but I'm not sure.  In any case, it's all
> in the book.
seconds above read cycles ... 40 seconds would be awfully long :-)
works in the following way: 8 times a 1 and 2 times a 0 bit written
several times after each other and reading 8 bit only if starting with
a 1 bit gets You in sync after at most 5 self sync bytes:
11111111001111111100111111110011111111001111111100........
^....... - already in sync
 ^....... ^.......  in sync
  ^.......^.......  ok
   ^.......^....... ^....... ok
    ^.......^.......^....... ok and so on
Some copy protection schemes wrote 36 cycle self sync bytes
i. e. 8 ones and 1 zero or 7 ones and two zeroes, some even used
three consecutive zero bits (forbidden by specs but working under
certain circumstances) 
Hope I did not bore You
wolfgang
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