Tandy TRS-80 Owner Manual & Programming Manual page 68
Color computer disk system
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Also See for TRS-80:
- Technical reference manual (204 pages) ,
- Service manual (60 pages) ,
- Owner's manual (16 pages)
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TECHNICAL INFORMATION
Sectors
Each
track contains 18
sectors,
numbered
1-18.
Each
sector
contains
338
bytes.
256
of
them
are
for
data.
The
remaining
bytes are
for
system
controls.
Byte#
Contents
0-55
System
controls
56-311
Data
312-337
System
controls
The hexadecimal
contents of the
system
control
bytes
are:
Byte#
Hexadecimal
Contents
0-7
00
8-10
F5
11
FE
12
Track
Number
13
00
14
Sector
Number
15
01
16-17
Cyclic
Redundancy Check <CRC)
18-39
4E
40-51
00
52-54
F5
55
FB
312-313
Cyclic
Redundancy Check (CRC)
314-337
4E
HOW
THE DATA
IS
ORGANIZED
Each
track contains
4,608 bytes
which
the
Com-
puter
can use
for
data:
18 sectors
per track
x 256 data
bytes per
sector
4,608 data bytes per track
The
data bytes
in
the 17th track contain the
disk's
directory.
The
data bytes
in
the
remaining 34
tracks are
for
disk
files:
Track
#
0-16
17
18-34
Disk
Files
Contents
of Track's
Data
Bytes
Disk
Files
Disk
Directory
Disk
Files
The Computer
divides
the
34
tracks
for
disk
files
into
68
granules. Since
each
track contains
two
granules,
one granule
is
2,304 bytes
long:
9
sectors in
V2
track
x 256 data
bytes per
sector
2,304 bytes
in
a granule
The Computer
uses granules
to
allocate
space
for
disk
files
in 2,304-byte
clusters.
Thus,
if
a
file
con-
tains
4,700
bytes,
the
Computer
allocates 3
gran-
ules (6,912 bytes) of disk
space
for
it.
The
location of
the
68
granules,
numbered
0-67,
is
as
follows:
Track
0,
Sectors
1-9
Track
0,
Sectors 10-18
Track
1,
Sectors
1-9
Track
16,
Sectors 10-18
Track
17,
Sectors 1-18
Track
18,
Sectors
1-9
Track
34,
Sectors 10-18
Granule
Granule
1
Granule
2
Granule 33
Directory
Granule 34
Granule
67
Note:
The
minimum
size
of
a
disk
file is
one granule
or
2,304
bytes.
A
di.sk
will
hold
a
maximum
of
68
disk
files.
Disk
Directory
The
directory
track (track
17)
contains
a
file
allo-
cation table
and
directory
entries.
The
sectors
on
this
track
which
contain
this
information
are:
Sector
#
Contents
2
File allocation table
3-11
Directory
entries
The
remaining
sectors in
the
directory
track are
for
future
use.
Directory Entries
The
9
sectors of
the directory
containing
directory
entries
(sectors 3-11) will
hold
up
to
72
entries.
Each
entry
is
32 bytes long
and
contains:
58
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