Shugart SA400L Minifloppy User manual

SA400L Minifloppy™
Diskette Storage Drive
Shugar
m
2D
I—'

TABLE OF CONTENTS
Page
TABLE OF CONTENTS i
LISTOFHGURES iii
LIST OF TABLES v
ABBREVIATIONS/MNEMONICS v
SECTION! INTRODUCTION M
1.1 General Description l-l
1.2 Specification Summary 1*1
1.2.1 Performance Specifications 1-1
1.2.2 Functional Specifications 1-1
1.2.3 Physical Specifications 1*2
1.2.4 Reliability Specifications 1-2
SECTION II ELECTRICAL INTERFACE 2-1
2.1 General 2-1
2.2 Signal Interface 2-2
2.3 PowerInterface 2-2
2.4 Input/Output Lines 2-2
2.5 FrameGround 2-2
SECTION III PHYSICAL INTERFACE 3-1
3.1 General
3.2 J1/PIConnector ^5
3.3 J2/P2 Connector
3.4 Frame Grounding
SECTION IV THEORY OF OPERATION J
4.1 General Operations
4.2 Head Positioning "2
4.3 Diskette Spindle Drive J o
4.4 Read/Write Head
4.5 Recording Format
4.5.1 General
4.5.2 Byte
4.6 Formats ^ o
4.6.1 Soft Sectored Recording Format
4.6.2 Track Layout 'e
4.6.3 Hard Sectored Recording Format
4.7 Drive Motor Control
4.7.1 Head Load
4.7.2 Single DriveSystem
4.7.3 MultipleDriveSystem
4.8 Index Detector
4.9 Track Zero Indication
4.10 Track Accessing
4.10.1 Stepper Motor "o
4.10.2 StepperControl -«
4.11 Read/Write Operations
4.12 Read/Write Head ,2
4.13 WriteCircuitOperation
4.14 Read Circuit Operation ^
4.15 Write Protect
SECTION V MAINTENANCE l'\
5.1 Maintenance Equipment e ,
5.1.1 AlignmentDiskette
5.1.2 Exerciser
5.1.3 Special Tools

5.2 Diagnostic Techniques 5-1
5.2.1 Introduction 5-1
5.2.2 Soft Error Detection and Conection 5-2
5.2.3 Write Error 5-2
5.2.4 Read Error 5-2
5.2.5 Seek Error 5-2
5.2.6 InterchangeError 5-2
5.3 Removalsand Replacements 5-3
5.3.1 Faceplate 5-3
5.3.2 DriveMotor Assembly 5-3
5.3.3 StepperMotor and Actuator Cam 5-3
5.3.4 Head and Carriage Assembly 5-3
5.3.5 Clamp Hub 5-3
5.3.6 Hub Frame Assembly 5-4
5.3.7 Write Protect Switch 5-5
5.3.8 Index Detector Assembly 5-5
5.3.9 Index LED 5-5
5.3.10 Track Zero Switch 5-5
5.4 Check. Adjustments, and Alignment 5-5
5.4.1 Test Point Locations 5-5
5.4.2 Head Amplitude Check 5-6
5.4.3 Motor Speed Adjustment 5-7
5.4.4 Motor Speed Adjustment (Using aFrequency Counter) 5-7
5.4.5 Track GO SwitchAdjustment 5-7
5.4.6 Carriage Limiter 5-9
5.4.7 Index Timing Adjustment (Soft Sector) 5-9
5.4.8 Index/SectorTiming Adjustment (Hard Sector) 5-10
5.4.9 Head/Radial Alignment 5-10
5.4.10 Write Protect Switch Adjustment 5-12
5.4.11 Read/Write Head Cleaning Procedure 5-12
5.5 Receiving Inspection 5-13
5.5.1 Philosophy 5-13
5.5.2 Procedure 5-13
SECTION VI MAINTENANCE DIAGRAMS 5-1
SECTION VII ILLUSTRATED PARTS CATALOG 7-J
7.1 Description
7.2 Cablesand CableConnections 7-1
7.3 Recommended Spare Parts Stocking Guide 7-1

LIST OF FIGURES
Figure Title Page
1-0 SA400LDrive 1-0
2-1 Interface Connections 2-1
2-2 InterfaceSignal Driver/Receiver 2-3
3-1 InterfaceConnectors - PhysicalLocations 3-1
3-2 J1 Connector Dimensions 3-2
3-3 J2 Connector 3-2
4-1 Functional Diagram 4-1
4-2 Byte (FMEncoding) 4-3
4-3 Recommended Soft SectorSingle Density (Even Boundaries) (FM) 4-3
4-4 MFM Recommended Format. 256 Bytes/16Records Per Track (IBM Type) 4-4
4-5 Recommended Hard Sector FM and MFM Formats 4-5
4-6 Motor Control Functional Diagram 4-6
4-7 Drive Select Functional Diagram 4-6
4-8 Index Detector Logic 4-7
4-9 Index Timing Diagram 4-7
4-10 Track GO Indication Diagram 4-8
4-11 Track (X) Timing Diagram 4-8
4-12 StepperControl Functional Diagram 4-9
4-13 Step TimingDiagram 4-9
4-14 Bit Cell 4-10
4-15 Basic Read/Write Head 4-11
4-16 Recorded Bit 4-11
4-17 Readinga Bit 4-11
4-18 IF and 2FRecordingRux and PulseRelationship 4-12
4-19 Read/Write Head 4-12
4-20 Write Circuit FunctionalDiagram 4-13
4-21 Read Circuit FunctionalDiagram 4-14
4-22 Write ProtectFunctional Diagram 4-14
5-1 HubFrameAdjustment 5-4
5-2 Test Point Locations 5-6
5-3 Motor Speed Adjustment 5-7
5-4 TrackZero Position 5-8
5-5 TrackZero Switch Adjustment 5-8
5-6 Carriage Limiter Clearance 5-9
5-7 IndexDetector Adjustment 5-10
5-8 SA400L Service Position 5-11
5-9 Index Timing 5-11
5-10 Correct Head Radial Alignment 5-12
5-11 Head Radial Alignment 5-12
5-12 Write Protect Switch Adjustment 5-13
6-1 Write Protect Inoperative 5-1
6-2
Diskette Not Rotating 5-2
6-3 Track (X) Indicator Inoperative 5-3
6-4
Drive Not Coming On Line 5-4
6-5
Index Pulse Inoperative 5-5
6-6 Drive PCB Logic Diagram 5-6
6-7 Read/Write Logic Diagram 5-6
6-8
Write Protect Logic Diagram 5-6
6-9
Motor Speed Control Logic Diagram 5-6
6-10
Power Diagram 5-7
6-11 400L (40 Track) Read/Write Schematic Diagram (2sheets) 6-9
7-1 SA400L Exploded View 7-2
7-2 DrivePCB Parts Location (P/N 25210) 7-4
7-3 Track 00 Switch Parts Location 7-7
7-4 Carriage/Head Parts Location 7-8
7-5 Hub Frame Parts Location 7-9
7-6
Head Load Solenoid Parts Location 7-10
ill

LIST OF TABLES
Table Title Page
2-1 DC Power 2-2
7-1 P/N to Figure - Reference 7-11
7-2 Cable and Cable Connections Part Numbers 7-12
7-3 Spare Parts Stocking Guide 7-13
ABBREVIATIONS / MNEMONICS
bp!
Bits per Inch
NHA
Next Higher Assembly
CK
Clock
NRZ
Non-Return to Zero
CRC
Cyclic Redundancy Check
R/W
Read/Write
fcl
Flux Changes per Inch
tpi
Tracks per Inch
FM
Frequency Modulation
TRK Track
ID
Identification
WG OFF Write Gate Off
IFC
illustrated Parts Catalog
WP
Write Protect
MFM
Modified FM
2F
Double Frequency
NHA
Next Higher Assembly
ABOUT THIS MANUAL
While every effort has been made to ensure that the information provided herein is correct, please notify us in the
event ofan error or inconsistency. Write any comments on the form in the back of this manual and send to.
Shugart
Technical Publications. MS 3-14
475 Oakmead Parkway
Sunnyvale. CA 94086
(408) 733 ()l(n)
This manual (P/N 39028-1) supersedes and makes obsolete the previous edition of this manual (P N 39028-0.
dated 5/81).
IV

39028-46
FIGURE 1-0. SA400L DRIVE

SECTION 1
INTRODUCTION
1.1 GENERAL DESCRIPTION
This manual provides depot level maintenance information necessary to maintain, trouble-shoot, and repair the
SA400L Minifloppy diskdrive manufactured by Shugart. Aseparate OEM manual (SA400LOEM
P/N 39019) is
available which describes the installation, interface, and power requirements useful for the applications of the
SA400L.
The SA400L floppy drives have these standard features:
a. Compact size and weight similar to most tape cassette units.
b. Single and double density capability.
c. 125/250 k bytes (unformatted) storage capacity.
d. 125/250 k bits/second transfer rate.
e. Low heat dissipation.
f. Positive media insertion to avoid media
damage.
g. EK^ drive motor (eliminates ac requirements).
h. Proprietary read/write head designed and manufactured byShugart.
i. Write protect circuitry,
j. Activitylight.
1.2 SPECIFICATION SUMMARY
1.2.1 Perfomance Specificatlona
Capacity Single Density Double Density
(in bytes) (FM) (MFM)
Unformatted
Per Disk 125,000 250,000
Formatted (16 Records/Track)
Per Disk 81.920 163,840
Per Track 2,048 4,096
Per Sector 128 256
Formatted (10 Records/Track)
Per Disk 102,400 204,800
Per Track 2,560 5,120
Per Sector 256 512
TransferRate 125 k bits/sec. 250 k bits/sec.
Latency (avg.) 100 ms
Access Time
Track-to-Track 20 ms
Average 286 ms
Settling Time 20 ms
1.2.2 Functional Specifications
RotationalSpeed 300 rpm
Recording Density 2768 bpi (FM) 5536 bpi (MFM)
Flux Density 5536 fci (FM) 5536 fci (MFM)
Track Density 48 tpi
1-1

Media Requirements
SA104 (soft-sectored)
SA105 (16 sectors, hard-sectored)
SA107 (10 sectors, hard-sectored)
Industry standard flexible diskette
Oxide on 0.(X)3 in. (0.08 mm) Myleur
5.25 in. (133.4 mm) square jacket
1.2.3 Physical Speclficadons
Operatiiig Shlppiii9 Storage
Environmental Limits
Ambient Temperature 50® to 115®F —40® to 144®F —8® to 117®F
(10.0® to 46.1®C) (-40® to 62®C) -22® to 47'C)
Relative Humidity 20 to 80% 1 to 95% 1 to 95%
Maximum Wet Bulb 85®F (29.4®C) No Condensation No Condensation
DC Voltage Requirements
+12 V ± 5% @ 1.80 A max
-I- 5 V ± 5% @ 0.70 A max
Mechanical Dimensions (exclusive of front panel)
Width = 5.75 in. (146.1 mm)
Height = 3.25 in. (82.6 m,m)
Depth = 8.25 in. (209.6 mm) Nominal
Weight = 3 lbs. (1.36 kg) Nominal
Power Dissipation
13.3 Watts (45.3 BTU/hr) Continuous (typical)
7.3 Watts (24.9 BTU/hr) Standby (typical)
1.2.4 Reliability Specificatioiis
Mean Time Between Failure: 8000 power on hours at 25% duty cycle
Mean Time to Repair: 30 minutes
Error Rates:
Soft Read Errors: 1 per 10' bits read.
Hard Read Errors: 1 per 10" bits read.
Seek Errors: 1 per 10® seeks
Media Life:
Passes per Track: 3.0 x 10®
Insertions: 30,(X)0+
1-2

SECTION II
ELECTRICAL INTERFACE
2.1 GENERAL
The electrical interfacebetween the SA400L drive and the host system is viatwo connectors. The first connector,
Jl, provides the signal interface (see figure 2-1). The second connector, J2, provides the dc power. Frame
ground is connected vai a faston connector located at the rear of the casting.
DRIVE
HOST SYSTEM
SPARE SIGNAL LINE
Jl
21
SPARE SIGNAL LINE
4
DRIVE SELECT 4^6 , 3
^INDEX/SECTOR
8 , 5
DRIVE SELECT 1^10 ,' 7
DRIVE SELECT 212 1' 9
.11
DRIVE SELECT 3
14
MOTOR ON
^
16
> 1J
DIRECTION SELECT ^
18
•ID
'17
'19
STEP
^20 ,
WRITE DATA
^
22
WRITE GATE
^
24
'41
'23
^ TRACK 00
26
^ WRITE PROTECT
28 ,
'4D
^READ DATA
30
SPARE SIGNAL LINE
32
SPARE SIGNAL LINE
34
•.Jl
»33
+ 5VDC
»•
J2
4
+12VDC
^1
• 3
, 0
n7^
FRAME "=
GROUND
FIGURE 2-1. INTERFACE CONNECTIONS
2-1

2.2 SIGNAL INTERFACE
Connection to J1 is through a 34 pin PCB edge card connector. The pins are numbered 1through 34 with the
even numbered pinson the component sideofthe PCB. The odd numberedpinsare on the non-componentside.
Pin 2 is located on the end of the PCB connector closest to the comer and is labeled 2. A key slot is provided be
tween pins 4 and 6 for optional connector keying.
2.3 POWER INTERFACE
DC power to the drive is via connector P2/J2 which is located on the non-component side of the drive PCB near
the spindle drive motor. The drive uses two voltages. Table 2-1 outlines the voltage and current requirements.
TABLE 2-1. DC POWER
P2
PIN
1
DC VOLTAGE
-I- 12VDC
+ 12 Return
+ 5 Return
+ 5 VDC
TOLERANCE
±0.6 VDC
±0.25 VDC
CURRENT
*1.80 A MAX
0.90 A TYP
0.70 A MAX
0.50 A TYP
MAX
RIPPLE (p to p)
100 mV
50 mV
•THE 12Vdc CURRENT IS COMPOSED OF THREE COMPONENTS; HEAD LOAD CURRENT, DISKETTE
DRIVE MOTOR CURRENT. AND PCB FUNCTIONS. EACH OF THESE COMPONENTS HAS THE
FOLLOWING CONTRIBUTIONTO THE 12 Vdc CURRENT REQUIREMENTS.
1. PCB FUNCTIONS (DRIVE "STANDBY" CURRENT) —0.4A TYP; 0.5 A MAX
2. HEAD LOAD (DRIVE SELECTED) -0.16 A TYP; 0.2 A MAX
3. DRIVE MOTOR: START(FOR 400 ms MAX) —1.0 A TYP; 1.1 A AMX
RUNNING 0.36 A TYP; 1.1 A MAX (MOTOR STALLED)
38028-17
2.4 INPUT/OUTPUT UNES
There are four output lines from the SA400L. The output signals are driven with an open collector output stage
capable of sinking a maximum of 48 mA at a logical zero level or true state with a maximum voltage of 0.4 V
measured atthe driver. When the line driver isa logical oneor false state the driver is off andthe collector cunentis
amaximum of 250 /lA.
There are nine Input lines to the SA400L. See figure 2-2 for the recommended circuit. These input lines have the
following electrical specifications.
True = Logical zero = Vin ± 0.0 V to +0.4 V @ lin = 48 mA (max)
False = Logical one = Vin + 2.5 Vto +5.25 V I® lin = 250/lA (open)
Input Impedance = 150 ohms
2.5 FRAME GROUND
It is important that the drive be frame grounded to the host system ac ground or frame ground. Failure to do so
may result in drive noise susceptibility. Refer to paragraph 3.4 for the procedure.
2-2

MAX 10 FEET
RIBBON OR
ISTED PAIR
I M/
—H Rl
rrw
150 0
39028-2S
FIGURE 2-2. INTERFACE SIGNAL DRIVER/RECEIVER
2-3/2-4 (blank)

SECTION ill
PHYSICAL INTERFACE
3.1 GENERAL
This section describes the physical connectors usedon the drive and therecommendedconnectors to be used with
them. See figure 3-1 for connector locations.
Drive PCS
Frame Connector
Amp P/N 60972-1
J1
Frame Ground^s^^
> Amp P/N 61664-1
P1 Connector
Scotchflex P/N
3463-0001 or
Amp P/N 583717-5
Amp P/N 350211-1
P2 Connector
AmpP/N 1-480424-0
3902S-1S
FIGURE 3-1. INTERFACE CONNECTORS• PHYSICAL LOCATIONS

3.2 J1/PI CONNECTOR
The dimensions for the J1 connector are shown in figure 3-2.
0.036 ± 0.004-
KEY SLOT
0.450 ±0.010
0.050" NOM
0.050" NOM
1.795 ±0.005
0.100" NOM
BOARD THICKNESS 0.062 ± 0.007"
FIGURE 3-2. J1 CONNECTOR DIMENSIONS
The recommended connectors for PI are tabulated below:
0.063" NOM (2X)
382304)7
TYPE OF CABLE
MANUFACTURER
CONNECTOR P/N
CONTACT P/N
Twisted Pair, #26
AMP
583717-5
1-583616-1
Flat Cable
3M "Scotchflex"
34634X)01
NA
3.3 J2/P2 CONNECTOR
The dc power connector, J2, is mounted on the non-component side of the PCB and is located near the drive
motor. J2 is a 4-pin AMP Mate-N-Lok connector, P/N 350211-1. The recommended mating connector (P2) is
AMP P/N 1-480424-0, using AMP pins P/N 61473-1. J2, pin 1, is labeled onthe component side of the PCB.
Wire used should be <^18 AWG. Figure 3-3 illustrates J2 connector as seenon the drive PCB from the non-
component side.
+ 12 VDC
00 0 0—
VDC
39211-16
FIGURE 3-3. J2 CONNECTOR
3.4 FRAME GROUNDING
The SA400L must be frame-grounded to the host system to ensure proper operation. If the frame of the drive is
not fastened directly to the frame of the host system with a good ac ground, a wire from the system ac frame
ground must be connected to the SA400L. For this purpose, a faston tab is provided on the drive at the rear of the
casting where a faston connector can be attached or soldered. The tab is AMP P/N 61664-1 and the mating con
nector is AMP P/N 60972-1 (see figure 3-1).
3-2

SECTION IV
THEORY OF OPERATION
4.1 GENERAL OPERATIONS
The SA400L Minifloppy Drive consists of read/write and controlelectronics, drive mechanism, motor control,
read/write head, and track
positioning mechanism. These componentsperform the following functions.
a. Interpret and generate control signals.
b. Move read/write head to the desired track.
c. Read and write data.
d. Maintain correct diskette speed.
The relationship and interface signals for the internal functions of the SA400Lare shown in figure 4-1.
The Head Positioning ActuatorCam positionsthe read/write head to the desired track on the diskette.
WRITE PROTECT (COM!
^EAD DATA
READ
LOGIC
DRIVE SELECT
WRITE DATA
WRITE GATE
WRITE PROTECT
WRITE
LOGIC
DRIVE SELECT
STEP
DIRECTION SELECT
DRIVE SELECT (4 LINES^
,TRACK 00
,INDEX/SECTOR
MOTOR ON
CONTROL
LOGIC
WRITE PROTECT
READ HEAD
WRITE HEAD
ACTIVITY LIGHT
HEAD LOAD SOLENOin
TRACK 00 (COM)
TRACK 00 (N/Oi
MOTOR CONTROL
TACHOMETER
STEPPER OA
STEPPER OB
STEPPER OC
STEPPER OD
INDEX/SECTOR DETECTOR
INDEX/SECTOR LED
FIGURE 4-1. FUNCTIONAL DIAGRAM
4-1
WRITE PROTECT
SWITCH
INDEX/SECTOR
DETECTOR
INDEX/SECTOR
LED
TEPPER MOTOR
TRKOO
SWITCH
DRIVE
MOTOR

The electronics packaged on the drive PCB contains:
a. Index Detector circuits
b. Head Position Actuator Driver
c. Read/Write Amplifier and Transition Detector
d. Step Control Logic
e. Track Zero Sensing circuits
f. Write Protect circuitry
g. Motor on/off circuitry
h. Motor speed control
4.2 HEAD POSITIONING
An electrical stepping motor drives the Head Position Actuator Cam which positions the read/write head. The
stepping motor rotates the actuator cam clockwise or counter-clockwise. The using system increments the step
ping motor to the desired track. Each step consists of two steps to the stepper motor for each step pulse supplied
on the interface.
4.3 DISKETTE SPINDLE DRIVE
The diskette dc drive motor rotatesthe spindle at300rpmthrough a belt-drive system. 50 or60 Hzoperation isac
commodated without any changes. A Clamping Hub moves in conjunction with the hub frame that precisely
clamps the diskette to the spindle hub. The motor is started by making the interface signal MOTOR ON true and is
stopped by makingthis signalfalse.
4.4 READ/WRITE HEAD
The read/write head is ceramic and in direct contact with the diskette. The head surface hasbeen designed to ob
tain maximum signal transfer toand from the magnetic surface ofthe diskette with minimum head/diskette wear.
The SA400L ceramic head isa single element read/write head with straddle erase elements to provide erased
areas between data tracks. Thus, normaltolerance between media and drives will not degrade the signalto noise
ratio and ensures diskette interchangeability.
Theread/write head is mounted on a carriage which is located onthe Head Position Actuator Camandis driven
through a cam follower. The diskette is held in a plane perpendicular to the read/write head by one platen located
on the base casting.
4.5 RECORDING FORMAT
4.5.1 General
The format ofthedata recorded onthe diskette is totally a function ofthehost system. Data canberecorded onthe
diskette using singleor double density.
4.5.2 Byte
A byte, when referring to serial data (being written onto or read from the disk drive), is defined as eight consecutive
bit cells. The most significant bit cell is defined as bit cell 0. The least significant bit cell is defined as bit cell 7. When
reference is made toa specific data bit (i.e., data bit 3), it is with respect to the corresponding bit cell (bit cell 3).
During a write operation, bit cell 0 of each byte is transferred to the disk drive first with bit cell 7 being transferred
last. Correspondingly, the most significant byte of data is transferred to the disk first and the least significant byte is
transferred last.
4-2

Whendatais being readback from the drive, bit cell 0 ofeachbyte will betransferred first with bit cell 7 last. As with
reading, the most significant byte will be transferred first from the drive to the user.
Figure 4-2 iilustrates the relationship of the bits within a byte
BYTE
C D C D C
rLTLTLrLn.
BIT CELL
0
^ MSB
BINARY
REPRESENTATION
DATA BITS 1
CLOCK BITS 1
BIT CELL
1
BIT CELL
2
C
a
BIT CELL
3
CDC
rLTLTL
BIT CELL
4
BIT CELL
5
CDC
n_nj-L
CDC
rLTLTl
BIT CELL
6
BIT CELL
7
LSB ^
BIT CELL
8
HEXADECIMAL
REPRESENTATION
DATA BITS (OA)
CLOCK BITS (FF)
39028-2
FIGURE 4-2. BYTE (FM ENCODING)
4.6 FORMATS
Tracks maybe formatted innumerous ways depending on the using system. The SA400L can useeitherhardor
soft sectored formats.
4.6.1 Soft Sectored Recording Format
In this format, the using system may record one long record or several smaller records. Each track isstarted bya
physical index pulse and each record is preceded by a unique recorded identifier. This type of recording is called
soft sectoring. Figure 4-3 illustrates the recommended single density (FM) formats. Figure 4-4 shows the recom
mended double density (MFM) format.
PHYSICAL
INDEX
HEX BYTE
NUMBER
OF BYTES
16 RECORDS
10 RECORDS
5 RECORDS
2 RECORDS
1 RECORDS
UPDATE WRITE
n
GAP
1
FF
16
•ID FIELD-
SYNC I AM I ID I CRC
00 FE E] H]
61
REPEATED FOR EACH RECORD-
GAP
2
•DATA FIELD-
SYNC 1 AM 1
DATA CRC
WG
OFF
GAP
3
GAP
4
8
El
USER
DATA
m
FF FF FF
6 I 6
128
256
512
1024
2048
26
19
70
499
101
69
54
5
1032
NOTES: 1. Track Number. Head Number. Sector Number, Sector Length.
2. IBM or Equivalent CRC Generator.
3. FB lor Data or F8 for Deleted Data.
s
390284
FIGURE 4-3. RECOMMENDED SOFT SECTOR SINGLE DENSITY (EVEN BOUNDARIES)(FM)
4-3

PHYSICAL
INDEX
NUMBER
OF BYTES
HEX BYTE
GAP 1
32
4E
UPDATE WRITE
•REPEATED FOR EACH NEW RECORD-
^ ID FIELD
SYNcIamI id I CRC
12 4 4 2
GAP
2
22
00 • m 0 4E
SYNC
12
00
•DATA FIELD-
AM
DATA I CRC
256
0 DATA [1]
NOTES: 1. First three bytes are Hex A1 with missing Clock Transitions between bits 4 and 5. Last byte is
Hex FE.
2. Track Number. Head Number. Sector Number. Sector Length (Hex 01).
3. IBM or Equivalent CRC
Generator.
4. Same as Note 1. except last byte = Hex FB.
I GAP
3
GAP
4
54 250
4E 4E 4E
38028-5
FIGURE 4^. MFM RECOMMENDED FORMAT. 256 BYTES/16 RECORDS PER TRACK (IBM TYPE)
4.6.2 Track Layout
Index isthe physical detector indicating one revolution ofthe media. Index is used to initiate format operations,
generate the READY signal inthe storage device, ensure one complete revolution ofthe media has been searched,
and for a deselectstorage device, signal aftera certainnumber of revolutions.
Gap 1 Gap 1 is from the physical index mark tothe identification (ID) field address mark sync. Gap 1
allows for physical index variation, speed variation, and interchange between storage devices.
ID Field Sync isa fixed number of bytes for separator synchronization prior to AM. Sync includes a
minimum of two bytes plus worst case separator sync up requirements.
ID Pre Addiesa Mark (MFM) isthree bytes of A1 with unique clock bits not written per encode
rules.
ID Address Mark (FM) isa unique byte to identify the ID field and not written per the encode
rules.
ID Address Mark (MFM) is one byte of FE and is written per the encode rules.
ID is a four byte address containing track number, head number, record number, and record
length.
CRC is two bytes for cyclic redundacy check (CRC).
Gap 2 Gap 2 is from ID CRC to data AM sync. Gap2 allows for speed variation, oscillator variation,
and erase core clearance to ID CRC bytes priorto write gate turn on for an update write.
Data Field Sync is a fixed number of bytes for separator synchronization prior to the AM. Sync includes a
minimum of two bytes plus worst case separator sync up requirements.
Pre Data Addreaa Mark (MFM) isthree bytes of A1 with unique clock bits not written per the
encode rules.
Data Address Mark (FM) isa unique byte to identify the data field and isnot written perthe
encode rules.
Data Address Mark (MFM) is one byteof FB or F8 and is written per the encode rules.
Data is the area for user data.
CRC is two bytes for cyclic redundancy check.
WG OFF (Write Gate Off) isone byte to allowfor write gate turn offafter an update write.
Gap 3 Gap3 is from WG OFF to next ID AM sync. Gap 3 allows for erase core to clear the data field
CRC bytes, speed and write oscillator variation, read preamplifier recovery time, and system turn
around time to read the following ID field.
Gap 4 Gap4 is the last gap prior to physical index. Gap 4 allows for speed and write oscillator varia
tion during a format write and physical index variation.
4-4

4.6.3 Haid Sectored Recording Format
In this format, the using system may record 16 or 10 sectors (records) per track. Each track isstarted by a physical
index pulse
and each sector is started by a physical sector pulse. This type of recording is called hard sectoring.
Figure4-5 Illustrates the hard sectored formats. The SA105 or SA107 minidiskette isto be used forthese formats.
All drive tolerances have been taken into account in developing these formats.
PHYSICAL!
SECTOR In
01
FF
16
SYNC AM ID
00 FB [D
6 1 4
DATA FIELD
(H
CRC
m
02
FF
PM.
HEX BYTE
NUMBER
OF BYTES
16 RECORDS
10 RECORDS.
MFM
HEX BYTE
NUMBER
OF BYTES
16 RECORDS
10 RECORDS
UPDATE WRITE
AA
16
128
256
FF OB Q] [2]
256
512
m
36
25_
AA
101
79
NOTES; 1. Track Number. Head Number. Record Number, Record Length.
2. User Data.
3. Oenerated by CRCOenerator (IBM or Equivalent).
FIGURE 4-5. RECOMMENDED HARD SECTOR FM AND MFM FORMATS
390284
4.7 DRIVE MOTOR CONTROL
The four main functions of the drive motor control are start/stop, speed control, over current protection, and
speed adjustment.
The motor used in the SA4(X)L isa dc drive motor and has a separate motor on and off interface line. Afterac
tivating the motoron line, a 400 ms delay mustbe introduced to allow proper motor speed before reading or
writing.
Whenmotoron isactivated to pin 16on the drive PCB,current will flow throughthe motor windings. Figure 4-6
shows the functional diagram of the motor speed control circuit. The motor speed control uses an integral
brushless tachometer. The output voltage signal from this tachometer is compared to a voltage frequency
reference level. The output from the vohage/frequencycomparator will controlthe necessary voltage to maintain
a constant spindle speed of 300 rpm. Motor speed adjustment changesthe reference voltage through a poten
tiometer.
4.7.1 Head Load
Whenthe shunt block position HLisshorted,the head will loadby energizing the head load solenoid when drive
select is brought to an active low. If theshunt block is positioned so HLisopen and MH isshorted, the head will
load with the motor on signal regardless of the state of drive select.
4-5

+ TACH IN
MOTOR
-TACH IN
-MOTOR OUT
SPEED ADJ
jr-WV
-MOTOR ON
FREQ/
+ MOTOR OUT
CONV
39028-7
FIGURE 4-6. MOTOR CONTROL FUNCTIONAL DIAGRAM
4.7.2 Single Drive System
With MX jumper shorted, the input tothe OR gate for output enable is ata low level. This causes the signal output
enable to always be true when the drive is powered on. Activating any drive select line will light the activity light
and enable reading and writing if the motor is running. See figure 4-7 for the logic required.
MOTOR ON
INPUT LINES
WRITE GATE
MX OPEN FOR MULTIPLE
DRIVE SYSTEM.
rri LEAVE SHORTED THE
liJ STRAPINTHE SHUNT
BLOCK FOR THE DRIVE
YOU WISH TO SELECT
mMH SHORTED: THE HEAD
WILL LOAD THE -MOTOR ON.
HL SHORTED: THE HEAD WILL
LOAD WITH -DRIVE SELECT
TO STEP
ONE-SHOT
PHASE A
ACTIVITY LITE
READ
READ ENABLE
READ PULSE
INDEX PULSE
OUTPUT ENABLE
WRITE PROT SWITCH
TRK 00 SWITCH
FIGURE 4-7. DRIVE SELECT FUNCTIONAL DIAGRAM
4-6
OUTPUT LINES
HEAOLOAO
39028-8

4.7.3 Multiple Drive System
There are four drive select lines. In multipledrivesystems, leave the jumper uncut in the shunt blockfor the drive
number desired. MXmust be cut forthe input and output to be daisey chained. WithMXcut. driveselect must be
true in order to activate output enable whichin turn gates the output lines, lights the activity light, and conditions
the input lines. Reading and writing can nowbe performed ifthe motor is running. Figure 4-7isthe drive select
functional diagram.
4.8 INDEX DETECTOR
Each time an index or sector hole is moved past the index photo detector, a pulse isformed. Thispulse ispresent
on the interface as index/sector at pin 8. Without a diskette in the drive, the output line
will be low so the using
system mustlookfora transition to be a valid signal. The detector outputisfedintoa schmidt trigger with a level
trigger latch back to maintain pulse stability while shaping thepulse. With output enable true, this pulse will beon
the interface as a negative goingpulse. See figures 4-8 and 4-9 for logic requiredand timings. Shownisthe output
from a soft sectored diskette.
<
[detector
o
©
©
40UTPUT ENABLE
FIGURE 4-a. INDEX DETECTOR LOGIC
-INDEX DETECTOR
200 ± IOOmSOC
SOFT SECTOR
- INDEX SECTOR
O
39028-9
39028-10
FIGURE 4-9. INDEX TIMING DIAGRAM
4.9 TRACKZERGINDICATIGN
Track00 signal (pin 26)isprovided to the using system to indicate whentheread/writehead ispositioned on track
zero. Figures 4-10 and 4-11 showthe logic and timing fortrackzeroindication. The track00 indication isprovided
whenthe head carriage actuatesthe track00 switch. Phase A is ANDed with drive select, which isthen ANDed
with the track (X) switch output. These conditions will cause a TRK 00 indication to the interface.
4-7