Shugart SA 400 minifloppy User manual

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SA400 rt&J
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© Copyright 1977 Shugart Associates

PREFACE
This service manual contains all the information
required to service the SA 400 MiniFloppy drive
in
the field. The service manual is divided into 3
sections:
Section I Theory of Operations
Section 2 Maintenance Manual
Section 3 Illustrated Parts Catalog
Each section contains its own Table of Contents.
For information on the SA 400 drive specifica-
tions, interfacing, track formats, and applications
notes refer to Shugart Associates OEM manual
PIN 54102.

Section 1

Table c)f Contents
1.0 Theory
of Operations 1
1.1
General Operations 1
1.2
Head Positioning . 1
1.3 Diskette Spindle
Drive.
2
1.4 Head/Write
Head .2
1.5 Hecording Format 2
1.6
Bit Cell 3
1.7
Byte.
3
1.8 Tracks.
4
1.9 Track Format 4
1.10 Sector Recording Format 4
1.11
Soft Sector Recording Format. 4
2.0 Drive
Motor Control 6
3.0 Drive Selection 7
3.1
Head
Load. 7
3.2
Singlle Drive System. 7
3.3 Mu Itiple Drive System.
7
4.0 Index Detector 8
5.0 Track Zero Indication .9
6.0 Track Accessing 10
6.1
Stepper Motor.
10
6.2 Stepper Control 10
6.3 Step
Out.
10
6.4 Step In Mode 10
7.0 Read/Write Operations
13
8.0 Read/Write
Head .
16
9.0 Write Circuit Operation
17
10.0
Read Circuit Operation 18
11.0 Write Protect
19
12.0 Interface .20
12.1 J1/P1Connector .20
12.2 D.C. Power 20
12.3 I
nput/Output Lines.
20

List of Illustrations
1.
Functional Diagram. 2
2.
Data Pattern 2
3.
Bit Cell 3
4.
Byte.
3
5.
Data Bytes 3
6. Hard Sector Format 4
7.
Soft Sector Format .5
8.
Motor Control Functional Diagram.
6
9. Drive Select Functional
Diagram.
7
10. Index Detector Logic 8
11. Index Timing Diagram. 8
12. Track 00 Indication Diagram 9
13. Track 00
Timing Diagram 9
14. Step
Out Logic 10
15. Stepper Control Functional Diagram
11
16. Step Timing Diagram 12
17. Step In Logic
12
1B. Bit Cell 14
19.
Basic Read/Write Head
14
20. Recorded
Bit
14
21. Reading A
Bit .15
22. IF and 2F Recording Flux and
Pu Ise Relationship 15
2:L Read/Write
Head.
16
24. Write Circuit Functional Diagram
17
25.
Read Circuit Functional Diagram 18
2B.
Write Protect Functional Diagram 19
27. D.C. Power 20
28. SA400 Interface Connections .
21
29. Interface Signal Driver/Receiver
21

1.0 THEORY OF OPERATIONS
1.1 GENERAL OPERATIONS
The SA 400 Minifloppy Drive consists of read/
write and
control electronics, drive mechanism,
motor control, read/write head, track positioning
mechanism,
and the removable Diskette. These
components perform the following functions:
•
Interpret and generate control signals.
•Move read/write head
to the desired track.
•Read and write data
•Maintain correct diskette speed.
The relationship and interface signals for the inter-
nal functions
of the SA 400 are shown in Figure 1.
The Head Positioning Actuator Cam positions the
read/write head to the desired track on the Disk-
ette. The Head Load Actuator loads the Diskette
against
the read/write head and data may then be
recorded or read from
the Diskette.
The drive has
two (2) PCB's, one is for the drive
motor control and the other is the drive PCB. The
electronics packaged on the drive PCB contains:
1.
Index Detector Circuits
2.
Head Position Actuator Driver
3. Head Load Actuator Driver
4. Read/Write Amplifier and Transition
Detector
5.
Step Control Logic
6. Track Zero Sensing Circuits
7. Write
Protect
The drive motor control PCB contains the following
electronics:
1. Motor on & off circuitry
2.
Motor speed control
1.2 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 clock-
wise or counter-clockwise. The using system incre-
ments the stepping
motor to the desired track. Each
step consists
of 2steps to the stepper motor for each
step pulse supplied
on the interface.

___ READ DATA
DRIVE SELECT
WRITE DATA
WRITE GATE
... WRITE PROTECT
DRIVE SELECT
STEP
DIRECTION SELECT. --..1
DRIVE SELECT (3 LINES)
..... TRACK 00
..... INDEX/SECTOR
_MOTOR ON __ . --..I
READ
LOGIC
WRITE
LOGIC
CONTROL
LOGIC
WRITE PROTECT (COM)
WRITE PR T C ~C
~"" _~::I~gROTECT
I ~ r---------------.
I ~~~
....... --+--j...:.:.R=..EA:.:::..D~HE~AD I ,.----_"....:~~:--_--.J
I
WRITE HEAD
ACTIVITY LIGHT
HEAD LOAD SOLENOID
TRACK 00 (COM)
TRACK 00 (N/OI
MOTOR ON
TACHOMETER
STEPPER </JA
STEPPER tPB
STEPPER <PC
STEPPER ¢O
INDEX/sECTOR LED
INDEX/SECTOR DETECTOR
FIGURE 1. FUNCTIONAL DIAGRAM
1.3 DISKETTE SPINDLE DRIVE
The Diskette D.C. drive motor rotates the spindle
at 300 rpm through abelt-drive system. 50 or 60
Hz operation is accommodated without any
changes. AClamping Hub moves in conjunc-
tion with the Hub frame that precisely clamps the
Di.skette to the spindle hub. The motor
is started
by making the interface signal
"motor on" true
and
is stopped by making this signal false.
1.1\ READIWRITE HEAD
The read/write head is aceramic head and is in
direct contact with the Diskette. The head sur·
face has been designed to obtain maximum signal
transfer to and from the magnetic surface
of the
Diskette with minimum Head/Diskette wear.
The SA
400 ceramic head is asingle element read/
write head with straddle erase elements to provide
erased areas between data tracks. Thus, normal
tolerance between media and drives will
not de-
grade the signal to noise ratio and insures Diskette
interchangeability.
The read/write head
is mounted on acarriage
which
is located on the Head Position Actuator
Cam and
is driven thm acam follower. The Disk-
2
ette is held in aplane perpendicular to the read/
write head
by one platen located on the base cast·
ing. The Diskette
is loaded against the head with
afelt load pad actuated by the head load solenoid.
1.5 RiECORDING FORMAT
The format of the data recorded on the Diskette is
totally afunction of the host system. Data is re-
corded on the Diskette using frequency modula·
tion
as t.he recording mode, i.e., each data bit re-
corded on the diskette has an associated clock bit
recorded with it, this is referred to as FM. Data
written
on and read back from the diskette takes
the form
as shown in Figure 2. The binary data
pattern shown represents a101. Two recording
frequencies are used.
IF which is 0 bit and 2F
which is a 1 bit. The IF frequency is 62.5 KHz
and
2F is 125.0 KHz.
I
DATA BITS
FIGURE 2. DATA PATTERN

1.6 BIT CELL
As shown in Figure 3, the clock bits and data bits
(if present) are interleaved. By definition, aBit
Cell
is the period between the leading edge of one
clock bit and the leading edge
of the next dock
bit. Abit cell time is 8/1 sec from clock to clock.
CLOCK BITS
_--L_
(
[)ATABr~
(If: PRESENT) ,
FIGURE 3. BIT CELL
1.7 BYTE
AByte, when referring to serial data (being written
onto or read from the disc drive), is defined as
eight (8) consecutive bit cells. The most significant
bit cell
is defined as bit cell 0and the least signifi-
cant
bit cell is defined as bit cell 7. When reference
is made to aspecific data bit (i.e., data bit 3), it is
with respect to the corresponding bit cell (bit cell 3).
During awrite operation,
bit cell 0 of each byte is
transferred to the disc drive first with bit cell 7be-
ing transferred last. Correspondingly, the most
significant
byte of data is transferred to the disc
first and the least significant
byte is transferred
last.
When data
is being read back from the drive, bit
cell 0
of each byte will be transferred first with
bit cell 7last.
As with reading, the most signifi-
cant byte will be transferred first from the drive
to the user. Figure 4illustrates the relationship
of the bits within abyte and Figure 5illustrates
the relationship
of the bytes for read and write
data.
~CELL8~~CELL;I:'TCELL: R:,TCELL: BlTCELL]
MSB I BIT CELL 1ILSB
BYTE--------------·~I
BINARY REPRESENTATION OF:
BIT CELL 0
DATA BITS
CLOCK BITS
HEXADECIMAL
REPRESENTATION
OF:
DATA BITS
CLOCK BITS
FIGURE 4. BYTE
b:ITiJ
YTE BYTE
LhLJ
01234567
,_-...lL....-_ ........ _......L __ .L-_-L_---' __ ........_........ _---JL.-._...L-_......I
1
BIT CELL 0OF BYTE 0 IS
FIRST DATA TO BE SENT
TO THE
DRIVE WHEN
WRITING AND FROM THE
DRIVE WHEN READING
FIGURE 5. DATA BYTES
3
1
BIT CELL 7OF BYTE 17 IS
LAST DATA TO BE SENT TO
THE
DRIVE WHEN WRITING
AND FROM THE DRIVE
WHEN READING

1.8 TRACKS
The SA 400 Minifloppy drive is capable of re-
cording up
to 35 tracks of data. The tracks are
numbered 0-34. Each track
is made available to
the read/write head
by accessing the head with
astepper motor and carriage assembly. Track
00
is the outer most track with track 34 being the
intermost track. Track accessing will be covered
in Section 3.
Basic Track Characteristics:
'1.10 HARD SECTOR RECORDING FORMAT
In this Format, the using system may record up to 10 or
]6 sectors (records) per track. Each track
is started
by aphysical index pulse and each sector
is started
by aphysical sector pulse. This type
of recording
is called hard sectoring. Figure 6shows some typ-
ical Sector Recording Formats. The using system
must do the sector separation. For additional in-
formation on sector separation and formatting re-
quirements. Refer to the SA
400 OEM Manual.
Tracks may be formatted in numerous ways and
is
dependent on the using system. The SA 400 can
use hard sector recording with
SAl05 and SAl07
media or soft-sectoring using SAl04 media.
No. bits/track
Bit per inch (inside)
Tracks per inch
Access time
1.9 TRACK FORMAT
25,000 bits
2,581 BPI
48 TPI
40 msec
'loll SOFT SECTOR RECORDING FORMAT
In this Format, the using system may record one
long record or several smaller records. Each track
is started by aphysical index pulse and then each
record is preceded
by aunique recorded identifier.
This type
of recording is called soft sectoring. Fig-
ure 7shows the soft sector format for
18 sectors
and 128 bytes. Refer to the SA
400 OEM Manual
for further formatting information.
HIEX BYTE
#OF BYTES
16 SECTORS
10 SECTORS
8SECTORS
5SECTORS
4SECTORS
2SECTORS
1SECTORS
SA 400 HARD SECTOR FORMAT
SECTOR SEPARATION DONE BY THE USING SYSTEM
FM RECOMMENDED FORMAT
PHY~CALSEC~R~'~~~~~~~~~~~ __ ~~ __ ~~~~~~~~~~~~~~
1-1I: .. --G-1-- ...... I .. .-I-D-... .. r----- OATAFIELD ------., .... 1 .. CRC ~M
IHEX HEX ~ CD HEX II
I00 FB FF
I16 1 2 tI
I128 48 I
I256 35 I
I256 115 I
I512
91 I
512 250
I1024 519 I
I2048 1058 I
UPDATE WRITE ~~~~~~~~~~~~~~.~~~.~~~~~~~~~~~~~~~
[2J -USER DATA
~J -GENERATED BY CRC GENERATOR (IBM OR EQUIV)
FIGURE 6. HARD SECTOR FORMAT
4