d88 file structure

D88STRUC.txt

D88 (D68/D77/D98) File Structure 
JPN Translations (http://jpntrans.nobody.jp)

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People Involved
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Translation, editing, etc.: Tokugawa Corporate Forum's Ashura
Hosting: noname345

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Start of Document
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-         All values are stored in little-endian format. 


Image File Structure: 
===================== 

          Disk 1 Header 
          Disk 1 Data 
            Track 0 
              Sector 1 Header 
              Sector 1 Data 
              ... 
            Track 1 
              Sector 1 Header 
              ... 
            ... 
          Disk 2 Header 
          Disk 2 Data 
          Disk 3 Header 
          ... 


Disk Header: 
============ 
Size:     688 or 672 bytes.    

Offset    Size             Meaning 
------------------------------------------------------------------------------------ 
00h       16(CHAR)         Disk name / comment. 
10h       1                00h (ASCII comment terminator). 
11h       9                Reserved (00h). 
1Ah       1                Write protect flag. 00h = normal. 10h = write protected. *1 
1Bh       1                Media flag. 00h = 2D, 10h = 2DD, 20h = 2HD. *2 
1Ch       4(DWORD)         Disk size (includes header size). 
20h       4(DWORD) * 164   Track table. Offset of each track from disk start. *3 
                           0 if track is unformatted or not used. *4 

*1        Any non-zero value should be treated as write protected. 
*2        The tool "1DDITT" also defines the flags 30h for 1D and 40h for 1DD disks. 
*3        Older tools only allowed up to 160 entries. -> header size is 672 bytes. 
*4        At least one of the many D88 tools is known to set all unused entries at 
          the end of the table to the end of the disk. 

-         To get the maximum number of tracks check the first non-zero value in the table. 
          It must be either 688 or 672. 
-         If the disk is unformatted only the first value in the table is set (688 or 672) 
          and the disk ends after the table. 


Disk Data Area: 
=============== 
Offset:   2A0h or 2B0h. 
Size:     variable. 

Track: 
------ 
-         Each track starts at the offset (relative to start of disk) found in the 
          track table. 
-         Tracks don't have any header data. 

Sector: 
------- 
Size:     10h (header) + variable data size 

Offset    Size          Meaning 
------------------------------------------------------------------------------------------ 
00h       1             C (cylinder) 
01h       1             H (head). 
02h       1             R (record/sector ID). 
03h       1             N (sector size). Bytes in sector = 128 << N. 
04h       2(WORD)       Number of sectors in track. *1 
06h       1             Density flag. 00h = double density. 40h = single density. 
07h       1             Deleted data (DDAM) flag. 0 = normal, 10h = deleted. 
08h       1             FDC status code. 00h = normal, B0h = Data CRC error, etc. 
09h       5             Reserved (00h). *2 
0Eh       2(WORD)       Actual data size following the sector header in bytes. 
---                     End of sector header. 
10h       (variable)    Sector data. 

*1        If this is not the same for all sectors within a certain track the disk is damaged. 
*2        Neko Project II stores values used for 1.44MB floppy disk emulation here. 

-         Actual data length might not match N field value. 
-         Sectors appear in the order in which they were read. 
-         Sector headers without data are possible. 
-         Sector header fields should be checked carefully since damaged image files are 
          all too common. 
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End of Document
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Thanks
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Nightcrawler - Whose interest made this document into reality.
Aoto(?) - For his original info about the D88.