From: msmcdoug@no.spam.iinet   
      
   Ralph Fox wrote:   
      
   > The 'ID Address Mark' and 'Data Address Mark' are preceded by a 'sync mark',   
   > which is a specific pattern of data bits and clock bits that never occurs in   
   > sector data.   
   >   
   > When the WD179x is formatting a disk (executing a 'write track' command),   
   > an F5 byte writes a 'sync mark' instead of an F5 data byte.  (The bytes   
   > F5 thru FE all have special meaning to the 'write track' command.)   
      
   You mean a missing clock transition between bits 4 & 5?   
      
   Regards,   
      
   --   
   |              Mark McDougall                | "Electrical Engineers do it   
   |     |   with less resistance!"   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)