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Fix 86F spec formatting
This commit is contained in:
RichardG867
@@ -9,109 +9,110 @@ Specification for v2.12
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All offsets are in hexadecimal.
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.. code-block:: none
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00000000: Magic 4 bytes ("86BF")
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00000004: Minor version (0C)
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00000005: Major version (02)
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00000006: Disk flags (16-bit)
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Bit 0 Has surface description data (1 = yes, 0 = no)
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This data indicates if the corresponding bit on the FM/MFM
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encoded surface is a normal bit or a special bit (weak bit
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or hole, depending on the other bit):
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0 = The corresponding FM/MFM encoded surface bit is normal
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1 = The corresponding FM/MFM encoded surface bit is either
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a weak bit or a hole:
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Corresponding FM/MFM encoded bit is 0:
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Hole (noise on read, not overwritable)
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Corresponding FM/MFM encoded bit is 1:
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Weak bit (noise on read, overwritable)
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Bits 2, 1 Hole (3 = ED + 2000 kbps, 2 = ED, 1 = HD, 0 = DD)
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Bit 3 Sides (1 = 2 sides, 0 = 1 side)
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Bit 4 Write protect (1 = yes, 0 = no)
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Bits 6, 5 RPM slowdown (3 = 2%, 2 = 1.5%, 1 = 1%, 0 = 0%)
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Bit 7 Bitcell mode (1 = Extra bitcells count specified after
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disk flags, 0 = No extra bitcells)
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The maximum number of extra bitcells is 1024 (which
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after decoding translates to 64 bytes)
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Bit 8 Disk type (1 = Zoned, 0 = Fixed RPM)
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Bits 10, 9 Zone type (3 = Commodore 64 zoned, 2 = Apple zoned,
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1 = Pre-Apple zoned #2, 0 = Pre-Apple zoned #1)
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Ignore if disk type is 0 (fixed RPM)
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Bit 11 Data and surface bits are stored in reverse byte endianness
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Bit 12 If set:
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If bits 6, 5 are not 0, they specify % of speedup instead
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of slowdown;
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If bits 6, 5 are 0, and bit 7 is 1, the extra bitcell count
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specifies the entire bitcell count
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For converting other stuff to 86F, I recommend to set this bit
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and bit 7 and clear bits 6 and 5,
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and just specify the entire bitcell count.
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00000008: Offsets of tracks
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Note that thick-track (eg. 360k) disks will have (tracks * 2) tracks, with each
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pair of tracks being identical to each other.
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Each side of each track is stored as its own track, in order (so, track 0 side 0,
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track 0 side 1, track 1 side 0, track 1 side 0, etc.).
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Track offset + 00000000: Track flags (16-bit)
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Bits 7, 6, 5 RPM:
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000 = 300 rpm
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001 = 360 rpm
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Bits 4, 3 Encoding:
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00 = FM
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01 = MFM
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10 = M2FM
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11 = GCR
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Bits 2, 1, 0 Bit rate, if encoding is MFM:
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000 = 500 kbps
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001 = 300 kbps
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010 = 250 kbps
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011 = 1000 kbps
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101 = 2000 kbps
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If encoding is FM, the bit rate is half that.
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If the bitcell count is present:
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Track offset + 00000002: Extra (or total, depending on disk flags) bit cells count (32-bit)
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If this specifies extra bit cells rather than total, it is a signed
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integer, and when negative, makes the track smaller.
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Track offset + 00000006: Bit cell where index hole is (32-bit)
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Track offset + 0000000A: FM/MFM/M2FM/GCR-encoded data (track length bytes)
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Track offset + 0000000A + track length: Surface description data if present (track length bytes)
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Else:
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Track offset + 00000002: Bit cell where index hole is (32-bit)
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Track offset + 00000006: FM/MFM/M2FM/GCR-encoded data (track length bytes)
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Track offset + 00000006 + track length: Surface description data if present (track length bytes)
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Track lengths if the bitcell count is not present or it does not represent total bit cells:
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Hole 0 (DD) or 1 (HD):
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2.0% RPM slowdown: 12750 words
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1.5% RPM slowdown: 12687 words
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1.0% RPM slowdown: 12625 words
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0.0% RPM slowdown/speedup: 12500 words
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1.0% RPM speedup : 12376 words
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1.5% RPM speedup : 12315 words
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2.0% RPM speedup : 12254 words
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Hole 2 (ED):
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2.0% RPM slowdown: 25250 words
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1.5% RPM slowdown: 25375 words
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1.0% RPM slowdown: 25250 words
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0.0% RPM slowdown/speedup: 25000 words
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1.0% RPM speedup : 24752 words
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1.5% RPM speedup : 24630 words
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2.0% RPM speedup : 24509 words
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Hole 3 (ED + 2000 kbps):
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2.0% RPM slowdown: 51000 words
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1.5% RPM slowdown: 50750 words
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1.0% RPM slowdown: 50500 words
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0.0% RPM slowdown/speedup: 50000 words
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1.0% RPM speedup : 49504 words
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1.5% RPM speedup : 49261 words
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2.0% RPM speedup : 49019 words
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1 word = 2 bytes (so 16 bits)
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If extra bit cells count is present and it indicates extra bit cells count:
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Track length = (Track length << 4) + Extra bitcells count
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If (Track length & 15)
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Track length + (Track length >> 4) + 1
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Else
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Track length + (Track length >> 4)
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If extra bit cells count is present and it indicates total bit cells count,
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then the total bit cells count become the track length, padded upwards to the
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nearest word in the file.
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00000000: Magic 4 bytes ("86BF")
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00000004: Minor version (0C)
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00000005: Major version (02)
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00000006: Disk flags (16-bit)
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Bit 0 Has surface description data (1 = yes, 0 = no)
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This data indicates if the corresponding bit on the FM/MFM
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encoded surface is a normal bit or a special bit (weak bit
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or hole, depending on the other bit):
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0 = The corresponding FM/MFM encoded surface bit is normal
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1 = The corresponding FM/MFM encoded surface bit is either
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a weak bit or a hole:
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Corresponding FM/MFM encoded bit is 0:
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Hole (noise on read, not overwritable)
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Corresponding FM/MFM encoded bit is 1:
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Weak bit (noise on read, overwritable)
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Bits 2, 1 Hole (3 = ED + 2000 kbps, 2 = ED, 1 = HD, 0 = DD)
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Bit 3 Sides (1 = 2 sides, 0 = 1 side)
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Bit 4 Write protect (1 = yes, 0 = no)
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Bits 6, 5 RPM slowdown (3 = 2%, 2 = 1.5%, 1 = 1%, 0 = 0%)
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Bit 7 Bitcell mode (1 = Extra bitcells count specified after
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disk flags, 0 = No extra bitcells)
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The maximum number of extra bitcells is 1024 (which
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after decoding translates to 64 bytes)
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Bit 8 Disk type (1 = Zoned, 0 = Fixed RPM)
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Bits 10, 9 Zone type (3 = Commodore 64 zoned, 2 = Apple zoned,
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1 = Pre-Apple zoned #2, 0 = Pre-Apple zoned #1)
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Ignore if disk type is 0 (fixed RPM)
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Bit 11 Data and surface bits are stored in reverse byte endianness
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Bit 12 If set:
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If bits 6, 5 are not 0, they specify % of speedup instead
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of slowdown;
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If bits 6, 5 are 0, and bit 7 is 1, the extra bitcell count
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specifies the entire bitcell count
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For converting other stuff to 86F, I recommend to set this bit
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and bit 7 and clear bits 6 and 5,
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and just specify the entire bitcell count.
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00000008: Offsets of tracks
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Note that thick-track (eg. 360k) disks will have (tracks * 2) tracks, with each
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pair of tracks being identical to each other.
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Each side of each track is stored as its own track, in order (so, track 0 side 0,
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track 0 side 1, track 1 side 0, track 1 side 0, etc.).
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Track offset + 00000000: Track flags (16-bit)
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Bits 7, 6, 5 RPM:
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000 = 300 rpm
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001 = 360 rpm
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Bits 4, 3 Encoding:
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00 = FM
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01 = MFM
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10 = M2FM
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11 = GCR
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Bits 2, 1, 0 Bit rate, if encoding is MFM:
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000 = 500 kbps
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001 = 300 kbps
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010 = 250 kbps
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011 = 1000 kbps
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101 = 2000 kbps
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If encoding is FM, the bit rate is half that.
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If the bitcell count is present:
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Track offset + 00000002: Extra (or total, depending on disk flags) bit cells count (32-bit)
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If this specifies extra bit cells rather than total, it is a signed
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integer, and when negative, makes the track smaller.
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Track offset + 00000006: Bit cell where index hole is (32-bit)
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Track offset + 0000000A: FM/MFM/M2FM/GCR-encoded data (track length bytes)
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Track offset + 0000000A + track length: Surface description data if present (track length bytes)
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Else:
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Track offset + 00000002: Bit cell where index hole is (32-bit)
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Track offset + 00000006: FM/MFM/M2FM/GCR-encoded data (track length bytes)
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Track offset + 00000006 + track length: Surface description data if present (track length bytes)
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Track lengths if the bitcell count is not present or it does not represent total bit cells:
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Hole 0 (DD) or 1 (HD):
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2.0% RPM slowdown: 12750 words
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1.5% RPM slowdown: 12687 words
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1.0% RPM slowdown: 12625 words
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0.0% RPM slowdown/speedup: 12500 words
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1.0% RPM speedup : 12376 words
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1.5% RPM speedup : 12315 words
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2.0% RPM speedup : 12254 words
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Hole 2 (ED):
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2.0% RPM slowdown: 25250 words
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1.5% RPM slowdown: 25375 words
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1.0% RPM slowdown: 25250 words
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0.0% RPM slowdown/speedup: 25000 words
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1.0% RPM speedup : 24752 words
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1.5% RPM speedup : 24630 words
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2.0% RPM speedup : 24509 words
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Hole 3 (ED + 2000 kbps):
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2.0% RPM slowdown: 51000 words
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1.5% RPM slowdown: 50750 words
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1.0% RPM slowdown: 50500 words
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0.0% RPM slowdown/speedup: 50000 words
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1.0% RPM speedup : 49504 words
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1.5% RPM speedup : 49261 words
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2.0% RPM speedup : 49019 words
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1 word = 2 bytes (so 16 bits)
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If extra bit cells count is present and it indicates extra bit cells count:
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Track length = (Track length << 4) + Extra bitcells count
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If (Track length & 15)
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Track length + (Track length >> 4) + 1
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Else
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Track length + (Track length >> 4)
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If extra bit cells count is present and it indicates total bit cells count,
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then the total bit cells count become the track length, padded upwards to the
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nearest word in the file.
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