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d88 file structure
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.
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