ATASI 3020 Installation and operation manual

SERIES 3000
OEM MANUAL
TABLE OF CONTENTS
1.0 INTRODUCTION
1.1 GENERAL DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . 1
1.2 DEVICE SPECIFICATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.2.1 ENVIRONMENTAL_?PECIFICATIONS . . . . . . . . . . . . . . . . . . . . . . . 2
1.2.2 RELIABILITY SPECIFICATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.2.3 PERFORMANCE
SUMMARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2.4
FUNCTIONAL SUMMARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.0 GENERAL OPERATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1 ORGANIZATION . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.2 READ/WRITE/INTERFACE PWA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.3 SPINDLE/EMA DRIVE PWA . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . 4
2.4 SERVO CONTROL PWA . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . .. . . . . 4
2.5 SPINDLE DRIVE MECHANISM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.6 AIR FILTRATION
SYSTEM . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . 5
2.7 POSITIONING MECHANISM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . 5
2.8 READ/WRITE HEADS AND MEDIA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.0 FUNCTIONAL OPERATION . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . 6
3.1 POWER SEQUENCING . .. . .. .. . . . .. .. . . . .. . .. . .. . .. .. .. . . . .. . . 6
3.2 DRIVE SELECTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.3 CYLINDER ACCESSING . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . 7
3.4 HEAD SELECTION . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.5 READ OPERATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.6 WRITE OPERATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
4.0 ELECTRICAL INTERFACE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
4.1 CONTROL INPUT LINES ....................................... 11
4.1.1 -WRITE GATE ........................................... 11
4.1.2 -HEAD SELECT .......................................... 11
4.1.3 -DIRECTION IN ......................................... 12
4.1.4
-STEP .................................................. 13
4.1.5 -DRIVE
SELECT 1-4 ....................................... 13
4.2 CONTROL OUTPUT LINES .................................... 13
4.2.1
-SEEK COMPLETE ....................................... 13
4.2.2 -TRACK 0 .............................................. 14
4.2.3 -WRITE
FAULT .......................................... 14
4.2.4
-INDEX ................................................. 14
4.2.5 -READY
................................................ 14
4.3 DATA TRANSFER LINES ........................................ 14
4.3.1
+/-MFM WRITE DATA .................................... 15
4.3.2
+/-MFM READ DATA .................................... 16
4.3.3 READ/WRITE
TIMING .................................... 16

4.4 -DRIVE SELECTED ........................................... . 17
4.5 POWER INTERFACE .......................................... . 18
4.6 CUSTOMER OPTION ........................................ . 18
5.0 PHYSICAL INTERFACE ........................................... . 19
5.1 J1/P1 CONNECTOR - CONTROL SIGNALS .................... . 20
5.2 J2/P2 CONNECTOR - DATA SIGNALS ......................... . 21
5.3 J3/P3 CONNECTOR - DC POWER ............................ . 22
5.4
J4/P4 FRAME GROUND ...................................... . 22
6.0 PHYSICAL SPECIFICATIONS ...................................... . 23
6.1
MOUNTING ORIENTATION .................................. . 23
6.2
MOUNTING HOLES ......................................... . 23
6.3 PHYSICAL
DIMENSIONS ............. , ....................... . 23
6.4 SHIPPING REQUIREMENTS
................................... . 23
7.0 SURFACE DEFECTS . . . . .. . . . . .. . . . . . .. . . . . .. . . . . . .. . . . . .. . . . . .. . . . 25
FIGURES:
1 POWER UP SEQUENCE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2
CONTROL SIGNALS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3
DATA SIGNALS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
4 TYPICAL
CONNECTION, 4 DRIVES .............................. 10
5 CONTROL SIGNAL RECEIVER/DRIVER COMBINATION ........... 11
6A STEP MODE TIMING (NORMAL) ............................... 12
6B STEP MODE TIMING (BUFFERED) ............................... 12
7 SELECT JUMPER, TERMINATOR AND )3 LOCATIONS .............. 13
8 INDEX
TIMING ............................................... 14
9
DATA LINE DRIVER/RECEIVER COMBINATION ................... 15
10A MFM ENCODING ............................................. 15
10B WRITE PRE-COMPENSATION PATTERNS ......................... 16
11 READ/WRITE DATA TIMING .................................... 17
12 CURRENT REQUIREMENTS .................................... 18
13 +12V STARTING CURRENT ..................................... 18
14 CONNECTOR LOCATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
15
J1 CONNECTOR DIMENSIONS ................................. 20
16 )2 CONNECTOR DIMENSIONS ................................. 21
17 )3 CONNECTOR LAYOUT ...................................... 22
18
MOUNTING DIMENSIONS .................................... 24
1.1
SECTION 1 - INTRODUCTION
GENERAL DESCRIPTION
The ATASI Series 3000 DISK DRIVES are random access storage devices
with two, three or four non-removable 5114 inch disks as storage media.
Each disk surface employs one moveable head to service its data tracks
and one disk surface is dedicated to continuous servo positioning data.
High performance and high unit reliability are achieved through the use
of a linear voice coil and a closed loop servo positioning system. The
inherent simplicity of mechanical construction and electronic controls
allows for maintenance free operation throughout the life of the drive.
The electronic PWA's are mounted outside the head disk area for quick
and simple field serviceability.
Mechanical and contamination protection for the heads, disk and
actuator are provided by a Disk Drive Module, (DOM) which is a sealed
mechanical enclosure with a self contained recirculating air filtration
system that supplies clean air and temperature equalization throughout
the DOM.
Shock and thermal isolation are provided by the combination of a heavy
duty steel chassis to which the DOM is shock-mounted, and internal
isolation within the DDM.
The bottom surface of the lowest disk contains the continuous servo data,
utilized to ensure precise positioning of the read/write heads.
The ATASI Series 3000 uses a ST506/4XX compatible interface.
The unit size and mountings are identical to the industry standard mini-
floppy disk drives and uses the same de voltages and connector.
KEV FEATURES:
• 30 Msec average seek time. (+3.0 Msec settling)
•
Storage capacities of 19.84, 33.07 and 46.30 megabytes unformatted.
• Spare Tracks. (10 per surface)
• Dedicated disk servo surface with servo guard band.
• Dedicated landing zone.
• Patented linear motor/closed loop servo head positioning.
• Double shock isolation.
• Thermal isolation.
• Industry Standard 5114-inch physical size and mountings.
• Same DC voltages as Standard 5114-inch drive.
• ST506/4XX compatible interface.
• 5.0 Mbit/sec data transfer rate.
1

1.2 DEVICE SPECIFICATION
1.2.1 ENVIROMENTAL SPECIFICATIONS
Environmental Limits:
Operating Temperature
Non Operating Temperature
Operating Humidity
Non Operating Humidity
Maximum Wet Bulb
Thermal Gradient
Operating Altitude
Operating Vibration
Non Operating Shock
Voltage Requirements:
+5VDC± 5% 1.0 Amp typical
10°
to 50° C
-40° to 60° C
10% to 80%
5% to 95%
25° c
(Non-condensing)
10° C per hour
0 to 10,000 feet
.5G at 10-500 Hz
30Gs
+12VDC±5'X, 4.5
Amps max (starting for 15 sec) 2.5 Amps typical
(For more information see Figure 12)
1.2.2 RELIABILITY SPECIFICATIONS
MTBF=12,000 POH
PM=NONE REQUIRED
MTTR=30
Minutes
Component Design life=5 Years
ERROR RATES:
Soft read errors=1 per 10/10th bits read
Hard read errors=1 per 10/12th bits read*
Seek errors=1 per 10/6th seeks
*Not recoverable within 16 re-tries
2
1.2.3
PERFORMANCE SUMMARY
Model 3020 3033 3046
Capacity Unformatted ( + 10 spare Cylinders)
Per Drive 19.84MB 33.07MB 46.30MB
Per Surface 6.61MB 6.61MB 6.61MB
Per Track 10.416KB 10.416KB 10.416KB
Capacity Formatted (+ 10 Spare Cylinders)
Per Drive 15.60MB 26.00MB 36.40MB
Per Surface 5.20MB 5.20MB 5.20MB
Per Track 8.192KB
8.192KB 8.192KB
Per Sector 256Bytes 256Bytes 256Bytes
Sectors/Track
32 32 32
Transfer Rate
5Mbit/sec
5Mbit/sec
5Mbit/sec
Seek Time
Track to Track 3.0ms 3.0ms 3.0ms
Average
30.0ms 30.0ms 30.0ms
Maximum 60.0ms
60.0ms
60.0ms
Settling 3.0ms 3.0ms 3.0ms
Average Latency 8.33ms 8.33ms 8.33ms
Start
Time 15 Sec 15 Sec
15 Sec
NOTE: The access times specified above are typical over a large number of
positionings. Due to the nature of a track following servo and some
customer unique parameters they should not be used as absolute
maximum values.
1.2.4 FUNCTIONAL SUMMARY
Rotation +/-1% 3600rpm 3600rpm
3600rpm
Recording max 8780bpi 8780bpi 8780bpi
Flux Density
8780fci 8780fci 8780fci
Track
Density
800tpi 800tpi 800tpi
Data Cylinders 645 645 645
Tracks 1905
3175 4445
R/W Heads 3 5 7
Disks 2 3 4
Index
3

SECTION 2 - GENERAL OPERATION
2.1 Organization
There are three basic functions that are required by a Disk Drive. They
are, to position the Read/Write heads over the desired track, to Write
Data,
and to Read Data. In the ATASI 3000 drives this is done with the
following electro-mechanical assemblies:
• Read/Write/Interface PWA
• Spindle/EMA Drive PWA
•
Servo Control PWA
• Spindle Drive Mechanism
• Air Filtration System
• Positioning Mechanism
• Read/Write Heads and Media
21 READ/WRITE/INTERFACE PWA
The READ/WRITE/INTERFACE PWA, to which all power, control and data
signals are connected, provides the following functions:
• POWER reception and internal voltage regulation.
• CONTROL INPUT SIGNAL reception and Internal distribution.
• CONTROL OUTPUT SIGNAL acrnmulation, sequencing and
transmission.
• READ/WRITE
SIGNAL bi-directional reception, conditioning and
transmission.
• FAULT detection and FAULT SIGNAL generation.
2.3 SPINDLE/EMA DRIVE PWA
The SPINDLE/EMA DRIVE PWA contains a dedicated MICROCOMPUTER
and is mounted directly to the bottom of the DOM mechanical
enclosure. It derives its power from the R/W/INTERFACE PWA and
provides the following functions:
• Power and speed control to the spindle drive motor.
• Power drive to the voice coil actuator, Electro Magnetic Actuator (EMA).
2.4 SERVO CONTROL PWA
The SERVO CONTROL PWA contains a dedicated MICROCOMPUTER
and is mounted to the top cover of the DOM mechanical enclosure, and
provides the following functions:
• Signal sequence control and monitoring during the power up operation.
• Receives the SERVO DATA that is read from the dedicated SERVO
DISK surface by the SERVO HEAD.
• Conditions the SERVO DATA and generates POSITION SIGNALS.
• Distinguishes between STEP and BUFFERED MODE seeks. In the case
of BUFFERED MODE, generate, detect and control the carriage
velocity to ensure the optimum arrival at the desired cylinder.
• Continuous position control while on track.
4
2.5 SPINDLE DRIVE MECHANISM
A brushless DC drive motor rotates the spindle at 3600 RPM± l'X,. The
motor is thermally isolated from the baseplate to minimize the tempera-
ture transfer. The motor, spindle and disk stack are dynamically balanced
to eliminate vibration. A dedicated MICROCOMPUTER provides
complete digital control of the spindle rotation and permits algorithm
control of motor start and stop.
2.6 AIR FILTRATION SYSTEM
The disks and read/write heads are fully enclosed in the DOM module
using an integral recirculating air system with an absolute filter to
maintain a clean environment. Integral to the filter is a port which permits
pressure equalization with the ambient air.
2.7 POSITIONING MECHANISM
The read/write heads are mounted on a ball bearing supported linear
carriage which is pcsitioned by a linear voice coil motor, driven by the
closed loop servo system.
2.8 READ/WRITE HEADS AND MEDIA
The recording media consists of a lubricated thin magnetic oxide coating
on a 130 mm diameter aluminum substrate. This coating formulation.
together with the low load force/low mass Winchester type heads,
permit reliable contact start/stop operations. Data on each of the data
surfaces is read or written by one read/write head. Each head accesses
645
data cylinders.
5

SECTION 3 - FUNCTIONAL OPERATION
3.1 POWER SEQUENCING
OCON
DISK UP
TO SPEED
-TRACK
o·
-READY•
The +5 and +12 volts de may be applied in any order. +12 volts must be
applied to start the spindle drive motor. A MICROCOMPUTER monitors
the disk rotation. At 3600 +/-1%, the heads will automatically recalibrate
to track 00. Under normal operation, thesignal -TRACK 0 will precede the
signals -READY and -SEEK COMPLETE by typically less than 30 µsec. The
-READY signal
is inhibited or disabled by any fault condition. The disk
drive can only perform read/write or seek functions following the setting
of the -READY signal. (see Figure 1 for the signal sequence).
... , ,.4---15 SEC MAX ___ .,., .. ,
I
:~11 SEC TYP...l
I ., ....................................... ...
• 1 SEC
I I TYP I
I AUTO REGAL ~Ill • I
I I I
I
-SEEK
COMPLETE•
I I =E' ,..--
........... ~..,..,..,._., ...... 3.0•µ•S•E•C ........... !-.~I ........................ .
: I I :..--
_____ ---...i __ .,._ __ .... ~----T-Y_P_1 __ S-EC ____ ..........., .. ______________ _
• -TRACK 0, -READYand -SEEK COMPLETE will notbe presentat the interface unless the
drive is selected
Figure 1 POWER UP SEQUENCE
6
3.2 DRIVE SELECTION
Drive selection occurs when one of the -DRIVE SELECT lines is activated.
Only the respective drive selected will respond to the signals from the
controller interface. There is also a radial select line which permanently
selects the drive (See Section 4.6).
3.3 CYLINDER ACCESSING
Read/Write head positioning is accomplished by:
• Activating the respective -DRIVE SELECT line.
• -READY
condition with -SEEK COMPLETE.
•
No FAULT conditions exist.
• Selecting the correct -DIRECTION.
• Pulsing the
-STEP line.
Each -STEP pulse will move the heads 1 cylinder. Motion i'> inward or
outward depending on the state of the -DIRECTION IN signal. A high
state indicates
inward toward the spindle and a low indicates outward
from the spindle. Seeks can be done in 3ms steps, or in the buffered mode
(see 4.1.4).
3.4 HEAD SELECTION
Read/write heads may be selected by placing the respective binary
address on the -HEAD SELECT lines.
3.5 READ OPERATION
Reading data is accomplished by:
• -DRIVE SELECT.
• Inactive -WRITE GATE .
• No FAULT conditions.
• Disk
drive is -READY and -SEEK COMPLETE.
• -HEAD
SELECT for the appropriate head.
• Present MFM READ DATA to the host controller.
3.6 WRITE OPERATION
Writing data is accomplished by:
• -DRIVE SELECT.
• Drive 1s -READY and -SEEK COMPLETE.
• -HEAD
SELECT for the appropriate head.
• No FAULT conditions.
• Activate -WRITE GATE and receive MFM WRITE DATA from the host
controller.
7

SECTION 4 -ELECTRICAL INTERFACE
The disk drive interface is divided into three catagories, each of which is physically
separate.
• CONTROL SIGNALS
•
DATA SIGNALS
• DC POWER
FLAT RIBBON OR TWISTED PAIR MAX 20 FEET
HOST SYSTEM DISK DRIVE
'""
1-
RESERVED 2
......
3~
-HEAD SELECT 22
~
4
-WRITE GATE
5-+
......
6
7---.
-SEEK COMPLETE 8
9---.
-
-TRACK 0
10
-WRITE FAULT
11~
-
12
13__.
-HEAD SELECT 2°
~
14
RESERVED (TO J2 PIN IT
15___.
16
17__.
~HEAD SELECT 2'
18
-INDEX
19----4.
-20
21~·
--READY
22 ....
23~·
-STEP 24
25----4.
-DRIVE SELECT 1
~
26
-DRIVE SELECT 2
27~·
28
-DRIVE SELECT 3
29~·
30
-DRIVE SELECT 4
31~·
32
33~·
-DIRECTION IN
34
,,
.....
1...i
J1/P1
-+5VDC 4 }
l
+5V RETURN
......
3
+12VDC 1
l
+12V RETURN 2
*
J3/P3
DC
GNDM
l TWISTED PAIR (20 GA or larger)
mMEGROUND FRAME GND
J4/P4
Figure 2 CONTROL SIGNALS
8
All control signals are digital (open collector TTL) and either provide signals to the
drive from the host controller or to the host controller from the drive via connector
J1/P1. The data transfer signals are differential and are connected via connector
J2/P2. DC power utilizes connector J3/P3. The one exception to the above is
-DRIVE SELECTED which is a digital signal, but is transmitted via J2/P2. Figures 2
through 4 show connector pin assignments and interconnection of cabling
between the disk drives and the host controller.
HOST SYSTEM
....
-
~
'lii'
•
FLAT CABLE OR TWISTED PAIR
20 FEET MAXIMUM
DRIVE SELECTED 1
RESERVED 3
SPARE
5
RESERVED (TO
J1 PIN 16)
7
SPARE 9
SPARE
10
tMFM WRITE DATA
13
-MFM WRITE DATA
14
......
GND
+MFM READ
DATA
17
-MFM READ DATA
18
GND
DISK DRIVE
2-
4-4.
6-4.
8--4.
11_.
12 ......
15 ......
16_.
19 .....
20~~
T
Figure 3 DATA SIGNALS
9
'"'
J2/P2
1.1

CONTROL
DATA
DRIVE #1
CONTROLLER
DATA
DRIVE #2
DATA
DRIVE #3
DATA
DRIVE #4
DC VOLTAGES-----'
FRAME GROUND ------'
• The last or only drive in the control cable string must have the terminator resistor pack
installed All other drives must have their terminators removed
Figure 4 TYPICAL CONNECTION, 4 DRIVES
10
4.1 CONTROL INPUT LINES
The control input signals are of two types: Those to be multiplexed in a
multiple drive system and those intended to do the multiplexing. fhe
multiplexed lines are -WRITE GATE, -HEAD SELECT, -STEP and -DIREC-
TION IN. The multiplexer is -DRIVE SELECT. The active state for all of
these lines is low or 0-+.7VDC. The inactive state is high OR +2-+SVDC.
The control input lines require the following specifications. (see Figure 5
for recommended circuitry).
PART OF +5V
TERMINATOR _
RESISTOR NETWORK '°llli.r
7438
•---- 20 FT (MAX) ---M
Figure 5
-
-
-
-
CONTROL SIGNAL RECEIVER/DRIVER COMBINATION
4.1.1 -WRITE GATE
This line, when active, enables write data to be written on the disk.
The inactive state enables data to be read from the disk. The
inactive state also enables seek operations.
4.1.2 -HEAD SELECT 20, 21, 22
These lines provide a means to select R/W heads in a binary coded
sequence. When all -HEAD SELECT lines are inactive, HEAD 0 is
selected. When the drive is not selected, R/W heads are deselected.
An illegal head address will deselect all heads.
11

4.1.3 -DIRECTION IN
This signal defines the direction of the carriage and R/W head
movement when the -STEP line is pulsed. An active -DIRECTION IN
defines a seek toward the spindle. An inactive -DIRECTION IN
defines a seek away from the spindle. (see Figures 6A and 6B for
signal timing).
I I
__ .. .,HI "'I ·---100 NS MIN
I I :
100 NS MIN ~ :..... I
I I I
I I I
I I I
-DIRECTION -~----• ! .. ~-------
14 3 MS MIN •1
--STEP
-SEEK
COMPLETE
-DIRECTION
--STEP
-SEEK
COMPLETE
-------w. w. 1.25µS MIN
_____ -----. ___ : .. r-100 NS MAX ~ ,.__ 1.0 MSc
FIGURE 6A STEP MODE TIMING (NORMAL)
I• 11
---.i :...,._ 100 NS MIN ---+t ..,____ 100 NS MIN
I I 11
·tmm ____ ... : l"~----- ...
-I I
I 2 5 µS MIN __ __..,~: :
1 500 NS MAX I I
____.u u ....... -
: I ~ :..._125µS MIN
---.i }4--100 NS MAX
:I L
FIGURE 68 STEP MODE TIMING (BUFFERED)
12
4.1.4 -STEP
This signal causes the R/W heads to move in the direction indicated
by DIRECTION IN. There are
two modes of STEP operation,
NORMAL and BUFFERED. In the NORMAL MODE the -STEP
pulses may occur at intervals not less than 3msec. The width of the
pulses may range from 1.25 µsec to 1.0 msec. In the BUFFERED
MODE the -STEP pulses can occur at intervals from 2.5 µsec to 500
µsec. The minimum pulse width in BUFFERED MODE is 1.25 µsec
(See Figures 6A and 6B for timing).
4.1.5 -DRIVE SELECT 1-4
This signal, when active, enables the respective drive interface
signals
to communicate with the host controller. Addresses are
customer selectable internal to the drive via Sl-4 on the
READ/WRITE/ INTERFACE PWA. (see Figure7 for jumper locations).
TERMINATOR
RESISTOR PACK
DRIVE SELECT I
JUMPERS PIN 1
6 ·'-----
AAAAA f·"
1111
~
+SV
RETURN
R;iy~Nv./+SV
+12Jj_
aooo]
\
J3
Figure 7 SELECT JUMPER, TERMINATOR AND J3 LOCATIONS
4.2 CONTROL OUTPUT LINES
I
The control output lines indicate the operational status, t1m1ng and
functional response
of the disk drive. These signals are enabled to the
host controller,
only while the drive is selected. (see 4.6 for the exception).
4.2.1 -SEEK COMPLETE
This <,1gnal become'> Jctive when the R/W head'> have settled on the
desired cylinder
at the end of a SEEK. READ or WRITE operations
may not be initiated
until -SEEK COMPLETE is true. -SEEK
COMPLETE will go inactive within 100 mec after the leading Pdge of
a -STEP pulse. or the first in a series of -STEP pulses. or if +5 VDC or
+12 VDC .ire lost momentarily.
13

4.2.2 TRACK 0
This signal becomes active when the disk drive's R/W heads are
positioned at TRACK 0, the outermost data track.
4.2.3 -WRITE FAULT
This signal becomes active when one of the following conditions
exists in a selected disk drive:
(a) -WRITE GATE true and NO WRITE CURRENT.
(b) WRITE CURRENT present
without -WRITE GATE.
(c) Multiple heads are selected.
(d)
When a valid selected head is shorted or open
(e) When-WRITE GATE is active with NO WRITE DATA
-WRITE FAULT is latched in the drive and can be cleared by a
power down or deselection of the drive
4.2.4 -INDEX
This signal is presented to the host controller from a selected disk
drive once for each revolution of the disk, and represents the
beginning of a track. (see Figure 8 for timing).
i..------16 6MS Norn ------_.I
I
I
LI LI
I I
---..I ,.._ 1.5 MS TYP
NOTE The only valid way to capture index 1s on the leading edge
Figure 8 INDEX TIMING
4.2.5 -READY
This signal in combination with -SEEK COMPLETE indicatesthat the
selected disk drive is READY to READ, WRITE or SEEK.
4.3 DATA TRANSFER LINES
These DATA TRANSFER LINES are DIFFERENTIAL in design, consisting of
two pairs of balanced signals used to transfer MFM DATA to and from the
selected disk drive. (see Figure 9 for recommended circuitry).
HIGH
TRUE
100 HIGH
TRUE
Figure 9
DATA LINE DRIVE/RECEIVER COMBINATION
4.3.1 +/-MFM WRITE DATA
DATA
PATTERN
MFM
ENCODED
DATA
FLUX
TRANSITIONS
DATA
WINDOW
CLOCK
WINDOW
MFM
DECODED
DATA
These two differential MFM (Modified Frequency Modulation)
signal lines define the code to be written on the track. The
transition
of +MFM WRITE DATA going more POSITIVE than -MFM
WRITE DATA causes a transition, or flux reversal on the disk by the
selected head. To ensure data integrity at the error rate specified,
the WRITE DATA transmitted by the host controller must be PRE-
COMPENSATED from cylinders 320 through 645. Optimum pre-
comp of both early and latedata is 12 nsec. (see Figure 10A for MFM
ENCODING and Figure 108 for WRITE PRE-COMP patterns. All
patterns not represented in Figure 108 are written on-time).
, ~--o _________ a _________ a ____ _
D D c c c c c
f..- 200ns BIT CELL
I
I I
~I 1-4-10ons
.JLJl ............ n ______________ __
Figure 10A MFM ENCODING
14 15

0 1 1
,.., ,..., t ...... +
-----IDL-..1 DL...
LwRITE DATA LATE
1 1 0
~
l WRITE DATA EARLY
0 0
._ __ _.c c
l WRITE CLOCK LATE
0 0 1
C D
l WRITE CLOCK EARLY
Figure 108 WRITE PRE-COMPENSATION PATTERNS
4.3.2 +/- MFM READ DATA
The transitions, "DATA" sensed by the selected head from a pre-
recorded track are transmitted to the host controller as MFM READ
DATA. The transition of +MFM READ DATA going more positive
than
-MFM READ DATA indicates the sensing of aflux reversal on
the disk by the selected head.
4.3.3 READ/WRITE TIMING
READ and WRITE functions require proper signal sequencing to
ensure DATA INTEGRITY. (See Figure 11 for proper signal timing).
16
-DRIVE SEL L'----------------------
-HD SEL
~
+MFM VALID
READ DATA
-WRITE GATE
WRITE CURRENT
~ 15 µSEC MAX (HEAD SWITCHING)
; ~ 25-50ns
J...20onsTYP
BIT CELL _ I I _ 8µ SEC MAX
--J r- WRITE/READ
"''
__ ...;.RliliEillclilo.,y.E.RY._
I ~
400ns-.J._I_• ______ ~,
MAX I I :
I I !
I I
200ns--..f I~
I
I
I
......
I
I
I
t4-1µs
I
I ~ ~50-150ns
+MFM WRITE DATA nnn
-------------------- ~---------
. I , __ 200ns TYP
~ BIT CELL
Figure 11 READ/WRITE DATA TIMING
4.4 -DRIVE SELECTED
The -DRIVE SELECTED line becomes true when the associated -DRIVE
SELECT matches the PHYSICAL ADDRESS of the disk drive, or the radial
option is selected.
17