Tandy 1000
Technical Reference Manual
8272A
SINGLE/DOUBLE DENSITY
FLOPPY
DISK
CONTROLLER
• IBM Compatible
in
Both Single and
Double Density Recording Formats
• Programmable Data Record Lengths:
128,
256,
512,
or 1024 Bytes/Sector
• Multi·Sector and Multi·Track Transfer
Capability
• Drives
Up
to
4 Floppy
or
Mini-Floppy
Disks
• Data Transfers
in
DMA or Non·DMA
Mode
• Parallel Seek Operations on Up
to
Four Drives
• Compatible
with
all Intel and
Most
Other Microprocessors
• Single·Phase 8 MHz Clock
• Single
+ 5 Volt Power Supply (::t 10%)
The 8272A
is
an LSI
Floppy
Disk
Controller
(FDC) Chip,
which
contains
the
circuitry
and
control
functions
for
inter-
faci'1g a
processor
to
4
Floppy
Disk
Drives. It is
capable
of
supporting
either
IBM 3740
single
density
format
(FM), or
IBM
System
34
Double
Density
format
(MFM)
including
double
sided
recording.
The 8272A
provides
control
signals
which
simplify
the
design
of
an
external
phase
locked
loop
and
write
precompensation
circuitry.
The
FDC
simplifies
and
handles
most
of
the
burdens
associated
with
implementing
a
Floppy
Disk
Drive
Interface.
The
8272A
is
a pin-
compatible
upgrade
to
the
8272.
'"
TERMINAL
I~
COUN1~
I~
ORO
~
~~-
;~~E
~~
j:::
'~:1~'OCl
CS-~
I
Cl~~
"cc-
GND_
Figure
1.
8272A
Internal
Block
Diagram
DRIVE
SELECTQ
DRIVE
SELECT
1
MFM
MODE
IfW"JSEEK
HEAD
LOAD
HEAD
SElECT
LOW CURRENT,IDlAECTION
FAULT
RESET/STEP
<0
Jvcc
RO[ 2
J9
JRW/SEEK
WAr
3
38
1 LCTIDIA
(SI
37
;FAISTP
Aof
5
J6
J
HDL
DBor
6 35
]RDY
08,[
7
J4
]
WPITS
DBll
8
JJ
"jFLTITRKO
DBJ[
9
J2
lPS
o
DB4[
10
31
jPS
1
DBd
"
3D
J
WR
DATA
oad
12
29
~
05
0
DBr[
13
28
]
OSl
oRal
"
27
]
HDSEL
5Acxl
"
Te
r
16
IDX[
17
INTf
I.
ClK[
"
GNol
20
Figure
2.
Pin
Configuration
Intel
Corpofalion
assumes
no
responsibllltJ'
tor
Ihe
use
of
any
cirCUIHy
olher
than
circuitry
embodied
In
an
Intel
produc~.
No
olher
Circuit
palent
licenses
are
implied
,
Intel
Corporation,
1982 ORDER
NUMBER
210606.001
6-224
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