Top 10k strings from myFDC765.rtf in <root> / doc / technical / specifications / FDC8272.zip /

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   1 often to check whether the FDC is ready, busy, or has returned an error etc.. The interval between successive reads must be minimal 12 \f1\fs24\'b5\f0\fs20 sec.= 42 Tstates of Z80 \par
   1 \uc1\pard\ulnone\f0\fs20\par
   1 When we want to read a full track, like a CAT file, only the first sector must be specified with the number of bytes to be read. When the CAT resides on track 0 (HC-IF1!) then also the Seek command can be skipped.                                                                                              \par
   1 To make interaction possible with the low level sector routine for HC2000 from BASIC, the data that has to end up in the \ul task file\ulnone  should first be poked in a data block as visible in the listing. In fact only the drive, side (=head) and track numbers are a (little) processed by the routine before they are put in the taskfile. \par
   1 The write-sector routine as given will only write 256 byte sectors. For 512 bytes sectors another ' writloop2' must be added. Counter B=0=256 again. See listing\par
   1 The sector-size number is 1=256, 2=512, 3=1024, 4=2048, 5=4096. For single density formats there also exist a sector-size 0=128. (Based on NEC uPD765A 1982)    \par
   1 The number of bytes to be written and/or read during each phase may differ for each of  the \par
   1 The FDC gives out important signals in its main status register. This register must be read\par
   1 The 8272 (=765A) type FDC works in 3 steps called phases:\par
   1 The 765 type FDC is capable of reading and writing multiple sectors and even multiple tracks. \par
   1 Note that sector lengths and sector numbers can be chosen individually during Format and that unknown disks may have ' irregularities' as a kind of copy-protection\par
   1 In fact the number of bytes to read or write must be determined by the programmer. The length of each sector however is stored in the sector ID on disk during Format, and read by the FDC during a read-sector command. The universal sector-read routine for HC2000 reads one byte of data outside the read-sector-data loop, and then checks the sector size in the relevant FDC register and from that calculates the remaining number of bytes to read from the given sector. When the number of data bytes to read is known (and constant) this detour can be left out! \par
   1 15 possible commands. \ul A datasheet will give a full list.\ulnone\par
   1 - In advance of, and during the \b Command phase \b0 all necessary parameters are collected \par
   1 - During the \b Result phase \b0 a \cf1 number of status bytes must(!) \cf0 be read. Here these bytes are\par
   1 - During the \b Execute phase \b0 the command is carried out. P.e. the data bytes from a sector\par
   1   stored in the \ul result file\ulnone . (By the 'getresult' routine)\par
   1   routine). (old version: dowrite)\par
   1   plus the required number of bytes \cf0 from the task file are fed to the FDC (the ' writcomm'\par
   1   must be read in this phase after a Read Sector command is issued. \par
   1   and stored in a table (here called \ul task file\ulnone ) and this phase ends \cf1 after the command byte \par
   1                                                                                  \par