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Tandy 1000 Technical Reference Manual

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Tandy 1000
8272A
Technical Reference Manual
number
read
off
the
diskette,
then
the
FDC
takes
data
from
the
processor
byte-by-byte
via
the
data
bus,
and
outputs
it
to
the
FDD
After
writing
data
into
the
current
sector,
the
Sector
Number
stored
in
"R"
is
incremented
by one, and the
next
data
field
is
written
into.
The FDC
continues
this
"Multi-Sector
Write
Operation"
until
the
issuance
of
a
Terminal
Count
signal.
If
a
Terminal
Count
signal
is
sent
to
the
FDC
it
continues
writing
into
the
current
sector
to
complete
the
data
field.
If
the
Terminal
Count
signal
is
received
while
a
data
field
is
being
written
then
the
reo
malnder
of
the
data
field
is
filled
with
00 (zeros).
1
~e
FDC
reads
the
10
field
of
each
sector
and
checks
"1e CRC
bytes.
If
the
FDC
detects
a read
error
(Incorrect
CRC) in
one
of
the
10
Fields,
it
sets
the
DE (Data Error)
flag
of
Status
Register
1
to
a 1 (high),
and
terminates
thE
Write
Data
Command.
(Status
Register
0
also
has
bits
7
and 6
set
to
0 and 1
respectively.)
:r)e
Wnte
Command
operates
in
much
the
same
manner
as
the
Read
Command.
The
following
items
are the
5ome;
refer
to
the
Read
Data
Command
for
details:
•
Transfer
Capacity
• EN (End
of
Cylinder)
Flag
•
ND
(No
Data)
Flag
•
Head
Unload
Time
Interval
• ID
Information
when
the
processor
terminates
com·
mand
(see
Table
2)
•
Definition
of
DTL
when
N =0
and
when
N " 0
In
we
Write
Data
mode,
data
transfers
between
the
proc·
essor
and
FDC
must
occur
every
31
IJS
in
the FM mode,
or,a
every
15 IJS In the
MFM
mode.
If
the
time
interval
between
data
transfers
is
longer
than
this
then
the FDC
set5
the
OR (Over Run) flag
in
Status
Register
1
to
a 1
(high). and
terminates
the
Write
Data
Command.
Fe)/
mln,.rlopples,
multiple
track
writes
are
usually
not
permlttea.
This
IS
because
of
the
tU'n·off
time
of
Ute
erase
heaa
cOils-the
head
sWitches
tracks
before
the
erase
head
lurns
off
Therefore
the
system
shOUld
'YPlcally
wall
1.3
mS
before
attempting
to
step
or
lnange
sideo
WRITE DELETED
DATA
ThiS
command
IS
the
same
as
the
Write
Data
Command
except
a
Deleted
Data
Address
Mark
is
written
at the
beginning
01
the
Data
Field
instead
of
the
normal
Data
Address
Mark
READ
DelETED
DATA
Trlis
command
IS
the
same
as
the
Read
Data
Command
except
that
when
the
FDC
detects
il
Data
Address
Mark
at the
beginning
of
a
Data
Field
(and SK = 0 (Iowl),
it
Will
read all the
data
in
the
sector
and
set
the
CM
flag
In
Status
Register
2
to
a 1 (high), and
then
terminate
the
comrr,and. If SK =
1.
then
the
FDC
skips
the
sector
with
the Data
Address
Mark
and reads the
next
sector
READ A
TRACK
This
command
IS
similar
to
READ
DATA
Command
except
that
the
entire
data
field
is
read
continuously
from
each
of
the
sectors
of
a track.
Immediately
after
encountering
the
INDEX
HOLE,
the
FDC
starts
reading
6-232
all
data
fields
on
the
track
as
continuou~
blocks
of
data
If
the
FDC
finds
an
error
in
the
ID
or
DATA
CRC
check
bytes,
It
continues
to
read
data
from
the
track.
The
FDC
compares
the
10
information
read
from
each
sector
with
the
value
stored
in
the
lOR,
and
sets
the
NO
flag
of
Status
Register
1
to
a 1 (high)
if
there
is
nO
comparison.
Multi-track
or
skip
operations
are
not
allowed
with
this
cornmand
This
command
terminates
when
EOT
number
of
sectors
have been read.
If
the
FDC
does
not
find
an ID
Address
Mark
on
the
diskette
after
it
encounters
the
INDEX
HOLE
for
the
second
time,
then
it
sets
the
MA
(missing
address
mark)
flag
in
Status
Register
1
to
a 1 (high),
and
terminates
the
command.
(Status
Register
0
has
bits
7
and
6
set
to
0
and
1
respectively.)
READ
ID
The
READ
ID
Command
is
used
to
give
the
present
pOSI-
tion
of
the
recording
head. The FDC
stores
the
values
from
the
first
10
Field
it
is
able
to
read. If
no
proper
ID
Address
Mark
's
found
on
the
diskette,
before
the
iN-
DEX
HOLE
IS
encountered
for
the
second
time
then
the
MA
(Missing
Address
Mark) flag in
Status
Register
1
is
set
to
a 1 (high),
and
if
no
data
is
found
then
the
ND
(No
Data)
flag
is
also
set
in
Status
Register
1
to
a 1 (high)
and
the
command
is
terminated
FORMAT
A
TRACK
The
Format
Command
allows
an
entire
track
to
be for-
matted.
After
the
INDEX
HOLE
is
detected,
Data
is
writ-
ten
on
the
Diskette:
Gaps,
Address
Marks, 10
Fields
and
Data
Fields.
all
per
the
IBM
System
34
(Double
Density)
or
System
3740
(Single
DenSity)
Format
are
recorded
The
particular
format
which
will
be
written
is
contrOlled
by
the
values
programmed
into
N
(number
of
bytes/sec·
tor), sc
(sectOrs/cylinder),
GPL
(Gap Length), and D
(Data
Pattern)
which
are
supplied
by the
processor
dur-
Ing
the
Command
Phase.
The
Data
Field
IS
filled
with
the
Byte
of
data
stored
in D The ID
Field
for
each
sector
is
supplied
by
the
processor;
that
is,
four
data
requests
per
sector
are
made
by
the
FDC
for
C
(Cylinder
Number),
H (Head
Number),
R
(Sector
Number)
and N
(Number
of
ByteS/Sector).
This
a!low~
the
diskette
to
be
formatted
with
nonsequential
sector
numbers,
if
desired
After
formatting
each
sector,
the
processor
must
send
new
values
for
C.
H,
R,
and
N
to
the 8272A
for
each
sec-
tor
on
the
track.
The
contents
of
the
R
Register
IS
in-
cremented
by
one
after
each
sector
IS
formatted,
thus,
the
R
register
contains
a value
of
R + 1 when
it
is read
dUfing
the
Result
Phase. ThiS
Incrementing
and
format-
ting
continues
for
the
whole
track
until
the
FDC
en-
counters
the
INDEX
HOLE
for
the
second
time.
where·
upon
It
terminates
the
command.
If
a
FAULT
signal
is
received
from
the
FDD
at
the
end
of
a
wflte
operation
tren
the
FDC
sets
the
EC
flag
of
Status
Register
0 to a 1 (high),
and
terminates
the
com·
mand
after
setling
bits
7
and
6
of
Status
Register
0 to 0
and
1
respectively
Also
the
loss
of
a READY
signal
at
the
beginning
of
a
command
execution
phase
causes
command
terminalion.
Table
9
shows
the
relat
lonshlp
between
N, SC,
and
GPL
for
variOUS
sector
sizes

Table of Contents

Other manuals for Tandy 1000

Preview: User Guide
User Guide337 pages
Preview: Programmer's Reference Guide
Programmer's Reference Guide251 pages
Preview: Basic Reference Manual
Basic Reference Manual411 pages
Preview: Owner's Manual
Owner's Manual46 pages

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Tandy 1000 Specifications

General IconGeneral
ProcessorIntel 8088
Processor Speed4.77 MHz
RAM128 KB (expandable to 640 KB)
Operating SystemMS-DOS 2.11
ManufacturerTandy Corporation
Release Year1984
StorageSingle or double 5.25" floppy disk drive (360 KB), optional hard drive
SoundTandy 3-voice sound
PortsParallel, Serial
GraphicsCGA (Color Graphics Adapter)
Graphics Modes320x200, 640x200

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