Color Computer CoCo SDC, Manual

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COCO SDC | 29
Following the File Header is the array of Track Records. Each track record begins with a 256
byte header and is then followed by 6250 bytes of raw track data. There are 150 bytes of unused
padding at the end of a track record which are included to align every track on a 512 byte
boundary within the file.
SDF Track Record
Track Header
Sector
ID Table
Sector Entry 0
Sector Entry 1
Sector Entry 2
Sector Entry 30
••
•
Track Header
Info Record
Sector
ID Table
Raw
Track Data
Padding
256
bytes
8 bytes
248
bytes
6250
bytes
150
bytes
8 bytes
per Entry
The fixed track size of 6250 bytes can accommodate either a single-density (125 kbps) or double-
density (250 kbps) track at 300 rpm. The SDF format does NOT support 8 inch floppy disks or
high density (500 kbps) images.
Any part of a track which is recorded in single-density has each byte written twice in succession.
This preserves the correct spacing of data on mixed-density tracks.
Contents of the SDF 256 byte Track Header
Byte Offset Length in
Bytes
Description
0 1 Number of used entries in the Sector ID Table.
1 7 Reserved. All seven of the remaining Info Record bytes should be set
to zero.
8 248 Sector ID Table.
Each entry in the Sector ID Table is 8 bytes in length and contains information about one sector
recorded on the track. The total size of the table is 248 bytes and can accommodate a maximum of
31 sector entries for a single track. All used entries must appear sequentially from the beginning
of the table. The unused entries must be filled with zeroes and placed at the end of the table.