Shugart SA410 User manual

SA41 0/460
96TPI
Single/Double-sided
Minifloppy™ Diskette
Storage Drives
^Shugart
uuu
3
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i

©SHUGART 1981
ALL RIGHTS RESERVED

TABLE OF CONTENTS
1.0 Introduction 1
1.
1
General Description 1
1.2 Specification Summary 1
1.2.1 Performance Specifications 1
1.2.2 Functional Specifications 2
1.2.3 Physical Specifications 2
1.2.4 Reliability Specifications 2
2.0 Functional Characteristics 3
2.1 Electronics 3
2.2 Drive Mechanism 3
2.3 Positioning Mechanism 3
2.4 Read/Write Head(s) 3
2.5 Recording Formats 3
3.0 Functional Operations 4
3. 1Power Sequencing 4
3.2 Drive Selection 4
3.3 Motor On 4
3.4 Track Accessing 4
3.4. 1Step Out 4
3.4.2 Step In 5
3.5 Side Selection (SA460 Only) 5
3.6 Read Operation 5
3.7 Write Operation 8
3.8 Sequence of Events 8
4.0 Electrical Interface 10
4. 1Signal Interface 11
4.1.1 InputLines 11
4.1.1.1 Input Line Terminations 12
4.1.1.2 Drive Select 1-4 12
4.1.1.3 MotorOn 12
4.1.1.4 Direction Select 13
4.1.1.5 Step 13
4.1.1.6 Write Gate 13
4.1.1.7 Write Data 13
4.1.1.8 Side Select (SA460 Only) 14
4.1.1.9 In Use (Option) 14
4.1.2 Output Lines 14
4.1.2.1 Track 00 14
4.1.2.2 Index/Sector 14
4.1.2.3 Read Data 14
4.1.2.4 Write Protect 15
4.1.2.5 Drive Status 15
4. 2Power Interface 16
4.2.1 Frame Ground 16
5.0 Physical Interface 17
5.1 Jl/Pl Connector 17
5.2 J2/P2 Connector 18
5.3 Frame Grounding 18
6.0 Drive Physical Specifications 20
61Mechanical Dimensions 20
6.2 Mounting 20

TABLE OF CONTENTS (CONT)
7.0 Recording Format 21
7. 1General 21
7.2 Byte 21
7.3 Formats 22
7.3.1 Soft Sectored Recording Format 22
7.3.1.1 Track Layout 23
7.3.1.2 Hard Sectored Recording Format 23
8.0 Customer Installable Options 25
8.1 Drive Select 27
8.2 The Door Lock Solenoid fOption) 28
8.3 Side Select 29
8.4 Drive Status 30
8.5 Write Protect 31
9.0 Operation Procedures 32
9.1 Minidiskette Loading 32
9.2 Minidiskette Handling 32
10.0 Installation of Packaging Materials 33

LIST OF ILLUSTRATIONS
Figure 1. SA410/460 96 TPI Minifloppys iv
2. SA410/460 Functional Diagram v
3. Track Access Timing 5
4. Read Initiate Timing 6
5. Read Data Timing (FM) 6
6. FM and MFM Code Comparisons 7
7. Write Initiate Timing 7
8. Write Data Timing (FM) 8
9. General Control and Data Timing Requirements 9
10. Interface Connections 10
11. Interface Signal Driver/Receiver 12
12. Step Timing 13
13. Write Data Timing (FM Encoding) 14
14. Index Timing (Soft Sectored Media) 15
15. Index/Sector Timing (SA115 or SA167 Media) 15
16. Index/Sector Timing (SA117 or SA167 Media) 15
17. Read Data Timing (FM) 15
18. Interface Connectors-Physical Locations 17
19. Jl Connector Dimensions 18
20. J2 Connector 18
21. Physical Dimensions 19
22. Recommended Mounting 20
23. Byte (FM Encoding) 21
24. Data Bytes 21
25. Recommended Soft Sector Single Density (FM) (Even Boundaries) 22
26. MFM Recommended Format -256 Bytes/ 16 Records Per Track (IBM Type) 22
27. Recommended Hard Sector FM and MFM Formats 24
28. Component Locations 26
29. Drive Select, Motor On and In Use 27
30. Door Lock From In Use or Drive Select 28
31. Side Select, Using Direction Select ...29
32. Drive Status 30
33. Write Protect 31
34. Carriage Stop 33
35. Door Retainer 34
36. Drive Container 35
37. Shipping Container 36
in

FIGURE 1. SA410/460 96 TPI MINIFLOPPYS
IV

WRITF
READ DATA READ
LOGIC
PROTECT
ASSM
-*
DRIVE
SELECT SIDE
SELECT
WRITE DATA
WRITE
LOGIC
*
WRITE GATE STEPPER
ACTUATOR
*SIDE SELECT
i
WRITE PROTECT —
«
iu
R/W HEAD
ASSM.
,R/WO
DRIVE R/W1 /• \
SELECT oDOOR
CLOSE
SWITCH
CONTROL
LOGIC
/
/
//
STEP v/
DIRECTION SELECT TRACK
00
-SENSOR
INDEX/
SECTOR
DETECTOR
DRIVE SELECT
MOTOR ON
IN USE *- /
/
DOOR LOCK _, /
»• IN USE
LED
TRACKOO / s.
«#
hNDEX/SECTOR
*\rf
DRIVE STATUS (DRIVE \^ y
[MOTOR JL-
i» V^T »- DOOR
IOOK
*SA460 ONLY
SOLENOID
(OPTION)
FIGURE 2. SA41 0/460 FUNCTIONAL DIAGRAM

1.0 INTRODUCTION
1.1 General Description
The compact SA410 single-sided and SA460 double-sided, 96 TPI, Minifloppy™ disk drives offer areliable, low
cost high performance solution for OEM data storage applications which require maximum capacity in aMinflop-
py. The SA410/460 Minifloppy drives are less than one-half the size of Shugart's standard SA801 floppy disk
drive, fit comfortably in the space allocated for most tape cassette units, and offer up to one megabyte of unformat-
ted capacity.
SA410/460 Minifloppy drives have these standard features: compact size -just 3.25" high x5.75" wide x8.25"
deep, and weight of three pounds; low heat dissipation; positive media insertion to keep door from closing on
media; rapid start DC drive motor with precision servo speed control and integral tachometer; direct drive stepping
motor actuator with precise HeliCam™ V-groove lead screw; ball bearing anti-backlash followers; read/write head
assembly; internal write protect circuitry; activity light, and solid die cast chassis.
The SA410 and SA460 are your best choices for word processing systems, microprocessor based systems, 'in-
telligent' calculators, program storage, personal computer systems and other applications where low cost higher
capacity random access data storage is required. The SA410/460 offers the most cost effective data storage of any
flexible media disk drive
.
Key Features
96 Track per inch
Precise HeliCam™ Actuator
0.5/1 MByte (unformatted) capacity
SA400/450 I/O compatibility
Same compact size and weight as the SA400/450 -similar to most tape cassette units
125/250 Kbits/second transfer rate
Single and double density capability
Low heat dissipation
Positive media insertion to avoid media damage
Rapid start DC drive motor (eliminates AC requirements)
Shugart Bi-Compliant™ read/write head assembly on SA460
Write protect circuitry
Activity light
Door Lock Solenoid
Drive Status
1.2 Specification Summary
1.2.1 Performance Specifications
Capacity
Unformatted
Per Disk
Per Surface
Per Track
Formatted
(10 Sector/Track)
Per Disk
Per Surface
Per Track
Transfer Rate
Latency (avg.)
Access Time (w/o settling)
Track to Track
Side to Side
Average
SA410
Single/Double Density
250/500 KBytes
250/500 KBytes
3.1/6.2 KBytes
204.8/409.6 KBytes
204.8/409.6 KBytes
2.56/5.12 KBytes
125/250 Kbits/sec
100 msec
6msec
158 msec
SA460
Single/Double Density
0.5/1 MByte
250/500 KBytes
3.1/6.2 KBytes
409.6/819.2 KBytes
204.8/409.6 KBytes
2.56/5.12 KBytes
125/250 Kbits/sec
100 msec
6msec
0.2 msec
158 msec

SA410 SA460
Settling Time 15 msec 15 msec
Motor Start Time 200 msec 200 msec
1.2.2 Functional Specifications
Rotational Speed 300 rpm 300 rpm
Recording Density 2788/5576 bpi 2961/5922 bpi
(inside track)
Flux Density 5576 fci 5922 fci
Track Density 96tpi 96tpi
Tracks 80 80
Index 11
Encoding Method FM/MFM FM/MFM
Media Requirements
soft sectored SA114 SA164
16 sectors hard sectored SA115 SA165
10 sectors hard sectored SA117 SA167
Industry standard flexible diskette
Oxide on 0.003 in. (0.08mm) Mylar
5.25 in. (133.4mm) square jacket
1.2.3 Physical Specifications
Environmental Limits Operating Shipping
Ambient Temperature =40°F to 115°F (4.4°C to 46.1°C) -40° to 144°F (-40°C to 62°C)
Relative Humidity =20% to 80% 1% to 95%
Maximum Wet Bulb =78°F (25.6°C) no condensation
Storage
-8°Fto 117°F (-22°C to 47°C)
1% to 95%
no condensation
DC Voltage Requirements
+12V ±5% @1.3A typical, 2.2A MAX
+5V ±5% @0.5A typical, 0.7A MAX
Mechanical Dimensions (exclusive of front panel)
Width =5.75 in. (146.1mm)
Height =3.25 in. (82.6mm)
Depth =8.25 in. (205mm)
Weight =3lbs. 3ozs. (1.44 Kg) Nominal)
Power Dissipation =
18.2 watts (62.1 BTU/Hr) Continuous (typical)
14.6 watts (49.8 BTU/Hr) Standby (typical)
1.2.4 Reliability Specifications
MTBF: 8000 POH under typical usage *
'Assumes the duty cycle of the drive spindle motor to be 25%
PM: Not required
MTTR: 30 minutes
Component Life: 5years
Error Rates:
Soft Read Errors:
Hard Read Errors:
Seek Errors:
1per 109bits read
1per 1012 bits read
1per 106seeks
Media Life:
Passes per Track: 3.0 x106
Insertions: 30,000 +

2.0 FUNCTIONAL CHARACTERISTICS
The SA410/460 Minifloppy disk drives consist of:
1. Read/Write and Control Electronics
2. Drive Mechanism
3. Precision Track Positioning Mechanism
4. Read/Write Head(s)
2.1 Electronics
The electronics are packaged on one PCB which contains:
1. Index Detector Circuits
2. Head Position Actuator Driver
3. Read/Write Amplifier and Transition Detector
4. Write Protect
5. Drive Select Circuits
6. Spindle Motor Control
The Head Positioning Actuator moves the read/write head{s) to the desired track on the diskette. The head(s) are
loaded onto the diskette when the door is closed.
2.2 Drive Mechanism
The DC drive motor under servo speed control (using an integral tachometer) rotates the spindle at 300 rpm
through abelt-drive system. An expandable collet/spindle assembly provides precision media positioning to ensure
data interchange. Amechanical interlock prevents door closure without proper media insertion, thus eliminating
media damage.
2.3 Positioning Mechanism
The read/write head assembly is accurately positioned through the use of aprecision HeliCam V-groove lead
screw with aball follower which is attached to the head carriage assembly. Precise track location is accomplished as
the lead screw is rotated in discrete increments by astepping motor.
2.4 Read/Write Head(s)
The glass bonded ceramic and ferrite read/write head(s) contain tunnel erase elements to provide erased areas bet-
ween data tracks. Thus normal interchange tolerances between media and drives will not degrade the signal to
noise ratio and diskette interchangeability is insured.
The read/write head(s) are mounted on acarriage which is located on precision carriage ways. The diskette is held
in aplane perpendicular to the read/write head(s) by aplaten located on the base casting. This precise registration
assures perfect compliance with the read/write head(s). The read/write head(s) is in direct contact with the
diskette. The head surfaces have been designed to obtain maximum signal transfer to and from the magnetic sur-
face of the diskette with minimum head/diskette wear.
2.5 Recording Formats
The format of the data recorded on the diskette is totally afunction of the host system, and can be designed around
the users application to take maximum advantage of the total available bits that can be written on any one track.
For adetailed discussion of the various recording formats refer to Section 7.0.

3.0 FUNCTIONAL OPERATIONS
3.1 Power Sequencing
Applying DC power to the SA410 or SA460 can be done in any sequence; however, during power up, the WRITE
GATE line must be held inactive or at ahigh level. After application of DC power, a100 ms delay should be in-
troduced before any operation is performed. Also, after powering on, initial position of the read/write heads with
respect to the data tracks on the media is indeterminant. In order to assure proper positioning of the read/write
heads after power on, aStep Out operation should be performed until the Track 00 line becomes active
(Recalibrate)
.
3.2 Drive Selection
Drive selection occurs when adrive's DRIVE SELECT line is activated. Only the drive with this line active will res-
pond to input lines or gate output lines. Under normal operation, the DRIVE SELECT line enables the input and
output lines and lights the Activity LED on the front of the drive.
3.3 Motor On
In order for the host system to read or write data the DC drive motor must be turned on. This may be accomplished
by activating the line MOTOR ON. A200 ms delay must be introduced after activating this line to allow the motor
to come up to speed before reading or writing can be accomplished.
The motor must be turned off by the host system by deactivating the MOTOR ON line. This should be done if the
drive has not received anew command within two (2) seconds (10 revolutions of diskette) after completing the ex-
ecution of a command. This will insure maximum motor and media life. Note: All motors in adaisy chain con-
figuration are turned on with MOTOR ON. Reference sections 4.1.1.2 and 4.1.1.3.
3.4 Track Accessing
Seeking the read/write heads from one track to another is accomplished by:
a. Activating DRIVE SELECT line.
b. Selecting desired direction utilizing DIRECTION SELECT line.
c. WRITE GATE being inactive.
d. Pulsing the STEP line.
Multiple track accessing is accomplished by repeated pulsing of the STEP line until the desired track has been
reached. Each pulse on the STEP line will cause the read/write heads to move one track either in or out depending
on the DIRECTION SELECT line. Head movement is initiated on the trailing edge of the STEP pulse.
3.4.1 Step Out
With the DIRECTION SELECT line at aplus logic level (2.5V to 5.25V) apulse on the STEP line will cause the
read/write heads to move one track away from the center of the disk. The pulse (s) applied to the STEP line must
have the timing characteristics shown in Figure 3.

DRIVE SELECT
DIRECTION SELECT
-s*- REVERSE
500 ns MIN.
FORWARD
H^
1MsMIN.
STEP
\^ tt 21 MS
r*W~ MIN
rLTLT5- h- Vs MIN.
VsMIN.
Vs MIN.
5.5 MS
MIN.
•6 MS MIN.
•Vs MIN.
FIGURE 3. TRACK ACCESS TIMING
3.4.2 Step In
With the DIRECTION SELECT line at minus logic level (0V to .4V), apulse on the STEP line will cause the
read/write heads to move one track closer to the center of the disk. The pulse (s) applied to the STEP line must
have the timing characteristics shown in Figure 3.
3.5 Side Selection (SA460 only)
Head Selection is controlled via the I/O signal line designated SIDE SELECT. Aplus logic level on the SIDE
SELECT line selects the read/write head on the side surface of the diskette. Aminus logic level selects the side 1
read/write head. When switching from one side to the other. A200/xs delay is required after SIDE SELECT
changes state before aread or write operation can be initiated. Side select should not change state for aminimum
of 1.1 msec after write gate is terminated. Figure 4shows the use of SIDE SELECT prior to aread operation.
3.6 Read Operation
Reading data from the SA410/460 minifloppy drive is accomplished by:
a. Activating DRIVE SELECT line.
b. Selecting Head (SA460 only).
c. WRITE GATE being inactive.
The timing relationships required to initiate aread sequence are shown in Figure 4. These timing specifications are
required in order to guarantee that the read/write heads position has stabilized prior to reading.
The timing of Read Data (FM) is shown in Figure 5.

DC POWER
MOTOR ON
DRIVE SELECT
STEP
WRITE GATE
SIDE SELECT
(SA460 ONLY)
VALID READ DATA
-200 MS MIN.
II
200^s MIN
1_ i
i
2^s MAX.
-200 MS MAX.
21 MS MIN.
~ff-
-r*-
-*f-
-*f-
~U
-Tf-
juuuuir^
1.1 MS
-MIN.
1.1 MSEC
MIN.
ITU
FIGURE 4. READ INITIATE TIMING
READ DATA-
4.0/iS
NOM.
4.0/tS
NOM.
LTU U
A=LEADING EDGE OF BIT MAY BE ±800 ns FROM ITS NOMINAL POSITION
B=LEADING EDGE OF BIT MAY BE ±400 ns FROM ITS NOMINAL POSITION
FIGURE 5. READ DATA TIMING (FM)

BIT
CELLS 11111
CDCDCDC CDC
fm n_ji_n__n_rLJT_ri n_ri_rL
*- 4.00 L
MS P
BIT
CELLS 1 1 111
CCCD
nnn_n__
*•—/
/
/
/
8.00 ^s
////////
JDDD DCC D/
mfm ipnn n n_n n_////
FIGURE 6. FM AND MFM CODE COMPARISONS
MOTOR ON
DRIVE SELECT
STEP
WRITE GATE
WRITE DATA
SIDE SELECT.
500 NS
MIN
8.00^s MAX
uu~u"irLi
8.00^s MAX.
iy h1.1 MS
MIN.
FIGURE 7. WRITE INITIATE TIMING

The encoding scheme of the recorded data can be either FM or MFM. FM encoding rules specify aclock bit at the
start of every bit cell (Refer to Figure 6) .MFM encoding rules allow clock bits to be omitted from some bit cells, with
the following prerequisites:
The clock bit is omitted from the current bit cell if either the preceding bit cell or the current bit cell contains adata
bit. See Figure 6.
In the above mentioned encoding schemes, clock bits are written at the start of their respective bits cells and data
bits at the centers of their bit cells.
3.7 Write Operation
Writing data to the SA410/460 is accomplished by:
a. Activating the DRIVE SELECT line.
b. Selecting Head (SA460 only).
c. Activating the WRITE GATE line.
d. Pulsing the WRITE DATA line with the data to be written.
The timing relationships required to initiate aWrite Data sequence are shown in Figure 7. These timing specifica-
tions are required in order to guarantee that the read/write head's position has stabilized prior to writing. Drive
select, or side select (SA460), may not change nor astep command be issued for aminimum of 1.1 msec after
write gate is returned to an inactive state (refer to paragraph 4.1.1.7).
The timing specifications for the Write Data pulses are shown in Figure 8.
Write data encoding can be FM or MFM. The write data should be precompensated 100 ns on all tracks to counter
the effects of bit shift. The direction of compensation required for any given bit in the data stream depends on the
pattern it forms with nearby bits.
3.8 Sequence of Events
The timing diagram shown in Figure 9shows the necessary sequence of events with associated timing restrictions
for proper operation.
WRITE DATA LJ
200 ns MIN
'2100 ns MAX. 8.00/tS U* 4.00/iS
FIGURE 8. WRITE DATA TIMING (FM)

POWER ON *$-
MOTOR ON
DRIVE SELECT
VALID TRK. 00
AND WRT. PROT.
OUTPUT
VALID INDEX/
SECTOR OUTPUT
DIRECTION
SELECT
STEP
WRITE GATE
WRITE DATA
VALID
READ DATA
SIDE
SELECT
(SA460ONLY)
•200 MS MIN.
-if-
500 ns
MIN.
*£
500 ns MAX. 1.1 MS MIN. —*A
$t
200 MS.
MAX
-500 ns MAX. M
19
6MS
MIN.
•VsMIN.
-Vs MIN.
^»>
•21 MS MIN-
Vs MIN. 1f~
5.5 MS
MIN.
500 ns MIN.
200 MS MIN
200MsMIN.
21 MS
MIN. '
21 MS
MIN
**
-8^s MAX W
innr*9
ITU ^
2/iS MAX -
200 MS MAX •
•200/xS MIN. -*f
uL11 MS
\MIN.
1.1 MS MIN.
LTLT
1.1 MS MIN.
FIGURE 9. GENERAL CONTROL AND DATA TIMING REQUIREMENTS

4.0 ELECTRICAL INTERFACE
The interface of the SA410/460 minidiskette drives can be divided into two categories:
1. Signal
2. Power
The following sections provide the electrical definition for each line.
Refer to figure 10 for all interface connections.
Refer to section 8.0 for description of options.
HOST SYSTEM DRIVE
DOOR LOCK (OPTION) 2
J1
1
i3
I5
i7
i9
i11
i13
i15
17
'19
>21
'23
>25
i27
i29
I31
i33
FLAT RIBBON (
OR TWISTED
PAIR |
TWISTED
PAIR
IN USE ^4
DRIVE SELECT 46
^, INDEX/SECTOR 8
DRIVE SELECT 110
DRIVE SELECT 212
DRIVE SELECT 314
MOTOR ON 16
DIRECTION SELECT 18
STEP 20
WRITE DATA _22
^*
WRITE GATE 24
_TRACK 00 26
^WRITE PROTECT 28
^READ DATA 30
SIDE SELECT (SA460 ONLY) w32
_DRIVE STATUS 34
^
+5VDC w4
J2
13
>2
+12VDC _1
rJr, 1?
////LOGIC
AC GND
GND
// FRAME —
GROUND —"LOGIC
GND
FIGURE 10. INTERFACE CONNECTIONS
10

4.1 Signal Interface
The signal interface consists of two categories:
1. Control
2. Data Transfer
All lines in the signal interface are digital in nature and either provide signals to the drive (input), or provide signals
to the host (output), via interface connector Pl/Jl.
4.1.1 Input Lines
The input signals are of 3types, those intended to be multiplexed in amultiple drive system, those which will per-
form the multiplexing and those signals which are not multiplexed and affect all the drives in adaisy chain system.
The input signals to be multiplexed are:
1. DIRECTION SELECT
2. STEP
3. WRITE DATA
4. WRITE GATE
5. SIDE SELECT (SA460 only)
The input signals which are intended to do the multiplexing are:
1. DRIVE SELECT 1
2. DRIVE SELECT 2
3. DRIVE SELECT 3
4. DRIVE SELECT 4
The signals which are not multiplexed are IN USE and MOTOR ON.
The input lines have the following electrical specifications. (See Figure 11 for the recommended circuit.)
True =Logical zero =Vin 0.0V to +.04V @40 ma (max)
False =Logical one =Vin +2.5V to +5.25V @250^a (open)
Input impedance =220/330ohms
11

7438
MAX 10 FEET
RIBBON OR
TWISTED PAIR
v-
I
I
I
7414
FIGURE 11. INTERFACE SIGNAL DRIVER/RECEIVER
4.1.1.1 Input Line Terminations
The SA410/460 has been provided with the capability of terminating the eight input lines listed below.
1. MOTOR ON
2. DIRECTION SELECT
3STEP
4. WRITE DATA
5. WRITE GATE
6. SIDE SELECT (SA460 only)
7. DOOR LOCK
8. IN USE
These lines are terminated through a220/330 ohm resistor pack installed in adip socket.
In asingle drive system this resistor pack should be kept in place to provide the proper terminations.
In amultiple drive system only the last drive on the interface is to be terminated. All other drives on the interface
must have the resistor pack removed. External terminations may also be used, then the user must provide the ter-
minations beyond the last drive and each of the eight lines must be terminated to +5VDC through a220/330 ohm
1/4 watt resistor.
4.1.1.2 DRIVE SELECT 1-4
The SA460 or SA410 is configured to operate with up to four drives in amultiplexed multiple drive system.
SINGLE DRIVE SYSTEM (MX shorting plug installed)
With the MS shorting plug installed, DRIVE SELECT when activated to alogical zero level will turn the motor on.
With MX shorted, the I/O lines are always enabled.
MULTIPLE DRIVE SYSTEM (MX shorting plug not installed)
Four separate input lines (DRIVE SELECT ,1, DRIVE SELECT 2, DRIVE SELECT 3and DRIVE SELECT 4) are
provided so that up to four drives in amultiplexed system may have separate input pins. Only the drive with its uni-
que DRIVE SELECT line active will turn its motor on, allow the drive to respond to multiplexed input lines and
enable the outputs to drive their respective signal lines. Alogic zero on the interface selects aunique drive select line
for adrive.
4.1.1.3 MOTOR ON
This input, when activated to alogical zero level, will turn on the drive motor allowing reading or writing on the
drive. A0.2 second delay after activating this line must be allowed before reading or writing. This line should be
deactivated, for maximum motor life, if no commands have been issued to the drives within two seconds nominal
(10 revolutions of the media) after completion of aprevious command. This time may be varied by the host system
to maximize system through-put and motor life depending on application.
12

As discussed in section 4.1.1.2, when MS is shorted the motor will turn on when the DRIVE SELECT line is ac-
tivated or if the MOTOR ON line is activated. Auser selectable option is available where by the motor will turn on
only when the MOTOR ON line is activated.
4.1.1.4 Direction Select
This interface line defines direction of motion the read/write heads will take when the STEP line is pulsed. An open
circuit or logical one defines the direction as "out" and if apulse is applied to the STEP line the read/write heads
will move away from the center of the disk. Conversely, if this input is shorted to ground or alogical zero level, the
direction of motion is defined as "in" and if apulse is applied to the STEP line, the read/write heads will move
towards the center of the disk.
4.1.1.5 Step
This interface line is acontrol signal which causes the read/write heads to move with the direction of motion as
defined by the DIRECTION SELECT line. This signal must be a logical zero going pulse with aminium pulse width
of 1/ts and alogical one for 5.5 ms minimum between adjacent pulses. Each subsequent pulse must be delayed by
6ms minimum from the preceeding pulse.
The access motion is initiated on each logical zero to logical one transition, or the trailing edge of the signal pulse.
Any change in the DIRECTION SELECT line must be made at least lfis before the trailing edge of the STEP pulse,
the DIRECTION SELECT logic level must be maintained 1/is after trailing edge of STEP pulse. Refer to Figure 12
for these timings.
DRIVE SELECT
DIRECTION SELECT •
500 ns MIN,'
STEP
^
FORWARD
Hh- -^5-
Vs MIN.
LTLTIJ"
Vs MIN Hh
REVERSE
Vs MIN.
Vs MIN.
5.5 MS MIN Vs MIN
•6 MS MIN.
FIGURE 12. STEP TIMING
4.1.1.6 Write Gate
The active state of this signal, or logical zero, enables Write Data to be written on the diskette. The inactive state or
logical one, enables the read data logic and stepper logic. Refer to Figure 7for timings.
4.1.1.7 Write Data
This interface line provides the data to be written on the diskette. Each transition from alogical one level to alogical
zero level, will cause the current through the read/write heads to be reversed thereby writing adata bit. This line is
enabled by Write Gate being active. Write Data must be inactive during aread operation .Refer to Figure 13 for tim-
ings.
13