Mitsubishi M4851 Installation and operation manual

MITSUBISHI
5 1/4" FLEXIBLE DISK DRIVE
MODEL M4851
OEM MANUAL
TJ2-G30?11 A
11/83

1.
1.1
1.2
1.2.1
1.2.2
1.2.3
1.2.4
1.2.5
2.
2.1
2.2
2.3
2.4
2.5
3.
3.1
3.2
3.3
3.4
3.5
3.6
3.7
3.8
4 •
4.1
4 .1. 1
4.1.2
4.1.3
4.1.4
4 .2'
4 •2 •1
5 •
5.1
5.2
5.3
M4851 OEM MANUAL
INTRODUCTION
General Description
Specifications-
Performance Specs
Functional Specs
Physical Specs
Environmental Specs
Reliability Specs
GENERAL OPERATION
System Operation
Electronics
Rotation Mechanism
Positioning Mechanism
Read/Write Heads
FUNCTIONAL OPERATION
Power-On Sequencing
Drive Selection
Positioning Operation
Side Selection
Re'ad Ope rat ions
Write Operations
Disk Insertion
Disk Removal
ELECTRICAL INTERFACE
Signal Interface
Cabling Method and Input Terminations
Line Drives and Receivers
Input Signal Lines
Output Signal Lines
Power Interface
DC Power
PHYSICAL INTERFACE
Signal Connector
DC Power Connector
Frame Ground Connector

.~ MITSUmSHIE~~R~
5.4 Interface Connector Location
6.1 Installation Orientation
6.2 Drive Dimensions
7. USER OPTIONS
7.1 DSO ... OS3
7.2 MX
7.3 HS
7.4 HM
7.5 HC
7.6 MM
7.7 MS
7.8 H-l
7.9 H-2
7.10 H-3
7.11 R-2
7.12 R-3
7.13 R-4
7.14 MC
7.15 RD-RS
7.16 DI
7.17 Write Protect Inversion
7.18 Terminations
7.19 Options Timing Examples
7.20 Summary Table
8.
8.1
8.1.1
8.1.2
8.1.3
8.2
8.3
8.3.1
8.3.2
9 •
9.1
9.2
RECORDING FORMAT
Recording Encoding
FM
MFM
MMFM
Track Format .
Error Detection and Correction
Write Errors
Read Errors
SHIPPING
Shipping Damage
Re-Shipping

1.0 INTRODUCTION
The Mitsubishi M4851 is a high-performance, double-sided, double
bit and double track density flexible disk drive using a standard
5.25-inch diskette, that provides maximum customer satisfaction
with high reliability and long service life.
- Main Features -
o
Only half the height of a standard mini-floppy drive.
o Has an unformatted ca?acity of one-half megabyte.
o Includes a diskette ejector for easy diskette removal.
o A
new circular gimbal spring in the
suspension mechanism greatly improves
performance.
read/write head
medium tracking
o The steel band, flat stepping motor drive system for
positioning achieves the best intertrack access time in its
class: just 6 ms.
o The maintenance-free, DC, brushless, direct-drive motor
obviates the belt replacement necessary for conventional
counterparts.
o Excellent media interchangeability, wide .off-track window
time margin, and high performance are maintained over wide
ambient temperature and relative humidity ranges.
. .
o The high-torque s~indle motor permits control by switching
on and off either the motor (starting time 250 ms) or the
head load solenoid (loading time less than SO ms).
I
o Dynamic clamping insures correct dis~ seating with easy disk
insertion.

~ MrrSUB~~EU~~C
1.1 GENERAL DESCRIPTION
o
The M4851 Flexible Disk Drive is a twin-head,
double-sided magnetic disk drive with an
unformated memory capacity of one-half megabyte
for double-density recordings.
o The M4851 reads and writes 5.25-inch, double-sided
diskettes in double-density format.
o The M485l employs· the unique Mitsubishi circular
gimbal spring for holding and loading the magnetic
heads to assure soft, steady contact with the
medium. This means excellent read/write operation
and a long service life for the medium. One of
the outstanding features of this mechanism is
reduction of the effects of jacket deformation and
thickness variations, thereby stabilizing
read/write performance.

1.2
1.2.1
SPECIFICATIONS
Performance specifications (Table 1-1)
Memory capacity
Unformatted
Disk
Per surface
Per track
Formatted
Disk
Per surface
Per track
Transfer rate
Average latency time
Access time
Track to track
Average
Set tling time
Head loading time
Motor starting time
Double Density
500 kilobytes
250 kilobytes
6.25 kilobytes
327.7 kilobytes
163.8 kilobytes
4096 bytes =
256 bytes x 16 sectors
250 kilobits/second
100 mS
6 mS maximum (unsettled)
103 mS (including settling
time)
25 mS maximum
50 mS maximum (including
settling)
250 mS maximum
Table 1-1 Performance Sgecifications

1.2.2
Functional specifications (Table t-2)
Recording density
Magnetic flux inversion density
Encoding method
Track density
Number of cylinders
Number of tracks
Number of heads
Rotation speed
Rotation period
Index
Media
Double Density
5922, bits per inch,
maximum
5922 FeI, maximum
MFM
48 tracks per inch
40
80
2
300 RPM
200 mSec
1
Double-sided 48 TPI,
double density,standard
5.25-inches diskette
Table 1-2 Functional Specifications

~ MrrSU~SHIE~~~C
1.2.3
Physical specifications .(Table 1-3)
DC power requirements
+5 V
+12 V
Heat dissipation
Physiqal dimensions
Height
Width
Depth
Front panel dimensions
Height
Width
Weight
+5 V 5%, 0.5 A ty?ical (seeking)
+12 V 5%, 0.5 A typical (seeking)
8.5 watts typical, seeking
5.0 watts typical, reading in
standby mode
4.0 watts typical motor off
(Except ~··.for front panel)
1.62 in (41 mm)
5.75 in (146 mm)
8 in (203.2 mm)
1.65 in (42.0 mm)
5 • 8 3 i n (14 8 . 0 mm)
2.9 lbs (1.3 kg)
Table 1-3 Physical Specifications

1.2.4 Environmental Specifications (Table 1-4)
Operating environmental
conditions
Ambient temperature
Relative humidity
Shock
Vibration
Altitude
Non-operatwng environmental
conditions
Ambient temperature
Relative humidity
Shock
Vibration
Altitude
Transportation environment
conditions (max 72 hours)
Ambient temperature
Relative Humidity
5 to 46 Deg. C (41 F to 115 F)
20% to 80% (Maximum wet bulb
temperature: 29 C (85 F)
2.5 G Max (20 mSec)
0.25 G Max (5-200 Hz.)
-300 to 3000 meters
-20 to 51 Deg. C (-4 F to 125 F)
5% to 95%
30 G Max (20 mSec)
3.0 G Max (5-200 Hz.)
-300 to 3000 meters
-40 to 62 Deq. C
(-40 to 144 Deg. F)
1% to q5~, non-condensing
Table l-4 Environmental Specifications

~.2.5 Reliability specifications (Table 1-5)
MTBF 10,000 POH minimum
MTTR 30 minutes
Unit life 5 years or 20,000 energized hours,
whichever comes first
Media
life
Insertion
Rotational
life
Tap-tap
Error rate
Soft read error
Hard read error
Seek error
4
3 x 10
or more
6
3.5 x 10 pass/track
5
10
on
the same
-9
10 bit
-12
10 bit
-6
to seek
spot
Table 1-5 Reliability Specifications
or more
of
a track

READ DATA
~iRITE GATE
WRITE DATA
niRITE PROTECT
SIDE SELECT
:N USE
;)IRECTION
SELECT
DRIVE SELECT
TR;"CK 00
READ
CIRCUIT
WRITE
CIRCUIT
CONTROL
LOGIC
L ___
READ/WRITE HEAD 0
READ/WRITE HEAD 1
T~CKOO
DETECTER
HEAD LOAD
SOLENOID
~--,---' ~'IR I TE PROTECT
DETECTOR
INDEX LED
,------
ACTIVITY
LED
DISK
~ -PRESE~T
SWITCH
INDEX DETECTOR
SPINDLE MOTOR ASSY
~----------- --------,--------
D.CMO~TR :
HOTOR /~~2 1
COCiTROL c==:::===-~~ l ~/
CIRCUIT .. ~ i
I I
L ____________________________ ~
Figure 2-1 M4851 Functional Diagram

2.0 GENERAL OPERATION
2.1 System Operation
The M485l Flexible Disk Drive consists of a' medium
rotating mechanism, two read/write
to position the read/write heads on
to load the read/write heads on the
circuits to read and write data,
components.
heads, an actuator
tracks, a solenoin
medium, electronic
and to drive these
The rotation mechanism clamps the medium inserted into
the drive to the spindle, which is directly cou~led to
the DC brushless motor, and rotates it at 300 rpm. The
positioning actuator moves the read/write head over the
desired track of the, medium. Then, the head loading
solenoid loads 'the read/write head on the medium to
read or write data.
2.2 Electronic Circuits
The electronic circuits driving the individual
mechanisms of the M485l are located on a single
printed-circuit board, which consists of the following
circuits:
o Line. driver and receiver that exchanges signals
'with the host system
o Drive selection circuit
o Index detection circuit
o Head positioning actuator drive circuit
o Head loading solenoid drive circuit
o Spindle motor control circuit
o Read/write circuit
o Write protect circuit
o Track 00 detection ci"rcuit
o Drive ready detection circuit
o Head selection circuit
o In use and panel indicator LED drive circuit

2.3 Rotation Mechanism
The diskette
direct-drive
300 RPM.
rotation mechanism uses a
motor to directly rotate the
2.4 Positioning Mechanism
DC brushless
soindle at
The positioning mechanism is a high-performance steel
band type.
The head carriage assembly is fastened to the steel
band which in turn is secured around the capstan of a
two-phase hybrid stepping motor; ·a 3.6 turn of the
stepping motor moves the read/write head one track in
the designated direction, thus positioning the
read/write head.
This drive system' is temperature compensated to
minimize read/write head deviations from the disk
tracks caused by ambient temperature change.
2.5 Read/Write Heads
The read/write heads use MnZn magnetic ferrite.
Each read/write head has three ferrite cores,
consisting of a read/write core and erase cores on both
sides of the read/write core to erase the space between
tracks (tunnel erase).
The two read/write heads, which are located face-to-
face with the disk between them, are mounted on
compliant, circular gimbal springs so that the heads
track the disk with qood contact to enable maximum
reproduction of the signals from the disk. ~he high
surface tracking ability of the circular gimbal keeps
the disk free of stress, and thus improves diskette
life.

3. a FUtJCT I CtlAL OPE RAT ION
3.1 Power On Sequencing
No read/write operation may be performed for a period
of 200 msec after the application of DC power to the
drive.
The read/write head may be positioned on an incorrect
track after switching the DC power on, so before
starting a read/write operation, perform a step out
operation until a track 00 signal is detected, thus
correctly positioning the head at a known position.
3.2 Drive Selection
The M485l daisy chain cablinq system permits connection
of multi91e drives with a single cable.
These drives are selected when the drive select lines
from the controller become active. Only the drive
whose drive select line is active sends and receives
signals to and from the host system. The select lines
on the drives must have different numbers if two or
more drives are connected. If the same number is
assigned, an operation error occurs due to interference
among the ou~put signals of the drives.
3.3 Positioning Operation
The see~operation which moves the read/write head to
the desired track selects a direction first, inward or
outward, with the polarity of the direction select
signal, and moves the head with the step signal. If
access to a track two or more tracks away is required,
step pulses are continuously sent until the head moves
to the desired track.
Head movement occurs with the trailinq edge of the step
pulse. Fig. 3-1 shows the operation timing.
3.4 Side One Selection
The read/write heads located on both sides of the
diskette are selected by the side one select signal.
When the side one select line is high, the side'O head
is selected. When it is low, the side 1 head is
selected.

3.5 Read Operation
Three modes of encoding, FM, MFM, or MMFM are used for
the data stored on media. FM is used for single-
density recording, and MFM or MMFM for double-density
recording. .
The required timing for FMread operations is shown in
Figs. 3-1 and 4-5. These timing specifications are
necessary for accurate read operation.
A comparison of the FM and MFM encoding modes is shown
in Fig. 3-2. See chapter 8 for a complete description
of encoding methods.
3.6 Write Operation
Write data can be encoded by either FM, MFM, or MMFM.
The M485l has good contact stability of the read/write
heads on the medium and employs high-performance
read/write heads, so no precompensation is necessary
for correcting the bit shift effect when writing data
in the MFM mode (double density). Specifically,
precompensation of 250 nSec or smaller should be used
on tracks 43 and above, and none should be used on
lower numbered tracks.
The required timing for write operation is shown in
Fig. 4-3. See chapter 8 for a complete description of
encoding methods.

~ ~rrSUB~~ELE~R~
3.7 Disk Insertion
The sequence of events that occur with disk insertion
are:
1) The user inserts the disk into the drive until
audible "click" is heard. This indicates that the
drive ejection mechanism has received the disk.
2) When the disk is fully inserted into the drive, a
mechanical switch is actuated, and the spindle
motor starts to rotate.
3) The user clamps the disk on to the rotating
spindle using the bridge handle. The handle is
moved until an audible click is heard.
4) The disk starts to rotate, and the index sensor
begins to detect pulses of light from the index
LED.
5) The index pulses are deteced in a m~n~mum period
of time; which switches the "current ready" and
nheld ready" logic to a true state. (If the disk
is not properly seated, this will not occur
because the index hole in the disk will never
allow light to strike the presise location
required to activate the photo-transistor that is
the index pulse senso~.) The spindle motor is
turned off.
6) Option jumper H-3 (or in some cases H-l) may be
used with o?tion He to load the head on to the
disk at this time. This is desirable if the user
wishes to eliminate the head load and settling
times associated with motor start/stop operation.
3.8 Disk Removal
To remove
the dis~ from the drive the user depresses
the front panel door Ela?, which releases the hridge
handle. The ejector mechanism then transports the .disK
out of the drive into the users finqers.
This action also resets the "held ready" status to a
false condition, which can be detected by having the
system controller poll the drive for its status (if the
R-3 option is used).

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VAUtl 'mCO~ 1-1 ~SOOns H}Il( -t
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INC2X I
FW1J ScU/(' I
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J'''' M:lJ -..J
~---------------------~--------.
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"'--lOOus MIN ---t L 4-u.~;1
--+--+-----+-o;--, ,J"..----tt· I
t---~Oms MIll " I
6:3am. MIN ~ a.o ... ~,~ .
, 'I J ~ l~O~;x ~p..J~1 -r--,-.~-Ctl-.s-· -MI-N--J~,-r--l-OOU2
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\~Aai) 1v;u.;:0 I ,v;>.;:,:o. :-U~
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Figure 3-1 Control and Data Timing

DATA I 1 I 1 I 1 o 1
DATA/III I 1I0I l!J! cis I 1]
/
/
/
(I
/
/
/
/
o
/
/
/
Figure 3.~ Comparison of FM and MFM encoding

4.0 ELECTRICAL INTERFACE
There are two kinds of electrical interfaces:
and DC power interface.
Signal interface
The signal interface sends and receives control signals and
read/write data between the M4851 and the host system via the
Jl/Pl connector.
The DC power interface drives the soindle drive motor of the
M485l, and supplies power to the electronic circuits and the
stepping motor which drives the read/write head positioning
mechanism via the J2/P2 connector.
The signals and pin arrangement of these two types of interfaces
are shown in Tables 3-1 and 3-2.
Source voltage
Pin number
+12 V DC
1
+12 V DC return
2
+5 V DC return
3
+5 V DC
4
Table 4-1 DC Power Connector Pin Arrangement (J2/P2)

~~MI~UBISHIE~~RIC
Signal
SPARE
IN USE
DRIVE
SELECT 3
INDEX
DRIVE SELECT 0
DRIVE
SELECT 1
DRIVE SELECT 2
MOTOR ON
DIRECTION
SELECT
STEP
WRITE DATA
WRITE GATE
TRACK
00
WRITE PROTECT
READ
DATA
SIDE
ONE SELECT
READY
Type
-----
Input
Input
Output
Input
Input
Input
Input
Input
Input
Input
Input
Output
Output
Output
Input
Output
Signal
Pin No.
2
4
6
8
10
12
14
16
18
20
22
24
26
°28
30
32
34
Ground/Return
Pin No.
1
3
S
7
9
11
13
l~
17
19
21
23
2S
27
29
31
33
Table 4-2 Signal Connector Pin Arrangement (Jl/Pl)