D77mod_format.md

D77mod Disk Image Format Specifications

Header (0x2b0 bytes)

offset	size	Contents
0x0000	17	image name (ASCIIZ)
0x0011	1	(mod)raw track data support flag (0x00=not support, 0x10=supported)
0x0012	8	reserve (0x00)
0x001a	1	write protect flag (0x00: no protect, 0x10: write protected)
0x001b	1	disk type (0x00: 2D, 0x10: 2DD, 0x20: 2HD)
0x001c	4	total disk image size
0x0020	4 * 164 (0x290)	sector data table (0-163 track)
0x02b0	4 * 164 (0x290)	(mod)track data table (0-163 track) 0=No track data or dirty track

(mod)Track data (+0x540 (=0x20+0x290+0x290))

offset	size	contents
0x0000	4	(mod)track data size
0x0004	variable	(mod)track data

Sector data (+0x2b0 when without track data, +??? with track data)

offset	size	contents
0x0000	1	C
0x0001	1	H
0x0002	1	R
0x0003	1	N
0x0004	2	# of sectors in this track
0x0006	1	density (0x00: double density, 0x40: single density)
0x0007	1	Deleted data (0x00: normal, 0x10: deleted data)XM7: 0x10 => RECORD_TYPE_ERR
0x0008	1	status (0x00: normal end, others: disk BIOS status) XM7: 0xb0 => Data CRC_ERR
0x0009	2	(mod)sector position (MFM byte)
0x000b	1	(mod)Status extension. 0x01 = ID_CRC error
0x000c	2	(mod)ID_CRC values
0x000e	2	sector size
0x0010	variable	sector data