Digital Equipment RX8 User manual

RX8/RX11
floppy disk system
maintenance manual
L....------digital equipment corporation. maynard. massachusetts-----......I

~, . .;.,
( RX8/RX11
floppy· disk ,ystem
maintenance:;}manual
(
EK-RXOI-MM-002
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digital equipment corporation · maynard. massachusetl;s

5179,15
Ist Edition, May 1975
2nd Printing (Rev), September 1975 (
3rd Printing, July 1976
4th Printing (Rev), December 1976
Copyright © 1975,1976 by Digital Equipment Corporation
The material. in this manual. is for informational
purposes and
is subject to change without notice.
Digital Equipment Corporation assumes
no respon-
sibility foriuty errors which may appear in this
manual.
Printed in U.s.A.
The following are ,trademarks of Digital Equipment
Corporation,Maynard, Massachusetts:
DEC
DECCOMM
DECsystem-l0
DECSYSTEM-20
DECtape
DEeUS·
DIGITAL
M{\SSBUS
PDP
RSTS
TYPESET-8
TYPESET-II
UNIBUS
c
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CHAPTER 1
1.1
1.2
1.2.1
1.2.2
1.2.3
1.2.4
1.2.5
1.3
1.3.1
1.3.2
1.3.3
1.3.3.1
1.3.3.2
1.3.3.3
1.3.3.4
1.4
1.5
'1.6
CHAPTER 2
2.1
2.2
2.2.1
2.2.2
2.2.3
2.2.4
2.3
2.3.1
2.3.2
2jj
2,3.4
2.3.5
2.4
2.4.1
2.4.2
2.4.3
2.4.3.1
2.4.3.2
2.4.4
2.5
2.5.1
2.5.2
2.5.3
2.5.3.1
2.5.3.2
2.~.4
CONTENTS
Page
GENERAL INFORMATION
INTRODUCTION
........................ ,.............. 1·1
PHYSICAL DESCRIPTION ..............,.................. 1-1
Rx8E/RXll Interfaces .................•..........••.. 1·2
Microprogrammed Controll~r ..........•....... 0 • • • • • • • • •• 1·2
Read/Write Electronics . . . . . . . . . . . .. . . . . . . . . . . . ~ , 0 , • • • •• 1 ~2
Electro·Mechanical Drive . . . , . . . . . . . . . . . . . " . . . . . . . . . . . ., 1·2
Power Supply ...•...... ,.......................... 1·3
SYSTEMS COMPATIBILITY ...............•.. , .•.. ,........ 1·3
Media •.......•.... , ............... " ....... , . ,. 1·3
Recording Scheme ................................... 1·10
Logical Format ....................... , ...... ; .... , .. 1·10 ,
Header Description ............................••.. 1·10
Data Field Description ........... , •...••...... , ..... HI
Track Usage ......•.. , .... , .........•..• , ...•.• 1·11
CRC Capability ............................•.... 1·12
APPLICABLE INSTRUCTION MANUALS ........... , ... , ... "., .. 1·12
CONFIGURATION ......... , ..........................• 1·12
SPECIFICATIONS
...... , .. ' ............ ~ .... ' •...... , .... 1·13
INSTALLATION
AND OPERATION
PURPOSE AND ORGANIZATION ............... , .. ' .. , ....... , 2·1
SITE PREPARATION ...............................•.... 2·1
Space .............. , ....... , .. , .... , ..••..... o. 2·1
Cabling ..... .' .... , .. , .. , ............. , .. , • . . . . . .. 2·1
AC Power ....,.....................,...... ~ . • , '! 2·1
Fire and Safety Precautions ;.........'.,....... 0 , • • • • • • • •• 2·2
ENVIRONMENTAL CONSIDERATIONS .... . . . . . . . . .. . . . . , . , . . • ., 2·2
General . . . . . . . . . . . . . . . . . . . , . • , . , . . . . . , . . . • • 0 • .., 2·2
Temperature, Relative Humidity .........•..............•. .. 2·3
Heat Dissipation ..................,...........".,.. 2-4
Radiated Emissions ....................,.. " . . . . . . • . .. 2·4
Cleanliness .......•........................•. 0 • • ., 2·4
INSTALLATION ......................•...• ,0 •• 0 • , ••• ,. 2-4
General .. . . . . . . . . . . . . . . . . . .. . . . 0 • • • • • .. • • • • • , • • • '0 2·4
Tools ............,.,................. 0 • • • • • • , " 2·4
Unpacking and Inspection .......,.".........,.,.,....,.. 24
Cabinet.Mounted . . . . . . . . . . . • . . .. . . . . . . : . . . . . , . . .. 24
Separate Container ................,.........,...,..' 2·6
Installation .......................,',.....,........ 2·6
OPERATION ............................,........... 2-8
Operator Control . . . . . . . . . , . . . . . , . . . . . . . • . • . . . . , . . . .. 2·8
Diskette Handling Practices and Precautions ...,....,.......,..... 2·8
Diskette Storage .......................,............. 2·12
Short Term (Available for Immediate Use) ......... , ........ , . 2~t2
LongTerm .. , .................. .' ..... ,., ... , .... 2·12
Shipping Diskettes ...........,.........,.........,.,. 2·12
iii

CHAPTER 3
3.1
3.2
3.2.1
3.2.2
3.2.2.1
3.2.2.2
3.2.2.3
3.2.2.4
3.3
3.3.1
3.3.2
3.3.3
3.3.4
3.3.5
3.3.6
3.3.7
3.3.8
3.4
3.4.1
3.4.2
3.4.3
3.5
3.6
CHAPTER 4
4.1
4.2
4.2.1
4.2.2
4.2.3
4.2.4
4.2.5
4.2.6
4.2.7
4.3
4.3.1
4.3.2
4.3.3
4.3.4
4.3.5
4.3.6
4.4
4.4.1
4.4.2
4.4.3
4.4.4
4.4.5
CONTENTS (Cont)
Page
RXll INTERFACE PROGRAMMING INFORMATION
REGISTER AND VECTOR ADDRESSES . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1
REGISTER DESCRIPTION
................................ ..
3-2
RXCS -Command and Status (177170) ...................... . 3-2
RXDB -Data Buffer Register (177172)
..... . . . . . . . . . . . . . . . . . . . 3-3
RXTA - RX Track Address
........................ . 3-3
RXSA -RX Sector Address
.......................... . 3-3
RXDB -RX Data Buffer
........................... . 3-4
RXES - RX Error and Status
......................... . 3-4
FUNCTION CODES .................................... . 3-5
Fill Buffer (000)
................................... . 3-5
Empty Buffer (001)
.................................. 3-5
Write Sector (010)
................................... 3-6
Read Sector
(all) .......................... ,. . . . . . ... 3-6
Read Status (101)
................................... 3-7
Write Sector with Deleted Data (110)
......................... 3-7
Read Error Register Function (111)
.......................... 3-7
Power Fail ....................................... 3-7
PROGRAMMING EXAMPLES ............................... 3-8
Read Data/Write Data
................................. 3-8
Empty Buffer Function
................................ 3-8
Fill Buffer Function
.................................. 3-11
RESTRICTIONS AND PROGRAMMING PITFALLS .................... 3-11
ERROR RECOVERY .................................... 3-11
RX8E INTERFACE PROGRAMMING INFORMATION
DEVICE CODES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
.. 4-1
INSTRUCTION SET . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2
Load Command (LCD) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
.. 4-2
Transfer Data Register (XDR) , . . . . . . . . . . . . . . . . . . . . . . . . . . .
.. 4-2
STR
.......................................... 4-3·
SER
........................................ 4-3
SDN
........................................ 4-3
INTR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3
INIT
........................................ 4-3
REGISTER DESCRIPTION
.............. . . . . . . . . . . . . . . .. 4-3
Command Register ........... . . . . . . . . . . . . . . . . . . . . . . .. 4-3
Error Code Register
.................................. 4-4
RXTA - RX Track Address
................•............. 4-5
RXSA -RX Sector Address
.............................. 4-5
RXDB -RX Data Buffer
............................... 4-6
RX Error and Status
.................................. 4-6
FUNCTION CODE DESCRIPTION ............................. 4-7
Fill Buffer (000)
.................................... 4-7
Empty Buffer (001)
......... , . . . . . . . . . . . . . . . . . . . . . . . . .. 4-8
Write Sector (010)
................................. 4-8
Read Sector (011)
................................. 4-9
Read Status (101)
................................. 4-9
iv
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4.4.6
4.4.7
4.4.8
4.5
4.5.1
4.5.2
4.5.3
4.6
4.7
CHAPtERS
5.1
5.1.1
5.1.2
5.1.3
5.1.4
5.1.5
5.2
5.2.1
5.2.1.1
5.2.1.2
5.2.1.3
5.2.1.4
5.2.1.5
5.2.2
5.2.2.1
5.2.2.2
5.2.2.3
5.2.2.4
5.2.2.5
5.2.2.6
5.2.3
5.2.3.1
5.2.3.2
5.2.3.3
5.2.3.4
5.2.3.5
5.2.3.6
5.2.3.7
5.2.3.8
5.2.3.9
5.2.3.10
5.2.3.11
5.2.3.12
5.2.4
5.2.4.1
5.2.4.2
5.2.4.3
CONTENTS (Cont)
Write Deleted Data Sector (110)
..
Read Error Register Function (111)
Power Fail ............ .
PROGRAMMING EXAMPLES .... .
Write/Write Deleted Data/Read Functions
Empty Buffer Function
......... .
Fill Buffer Function . . . . . . . . . .
RESTRICTIONS AND PROGRAMMING PITFALLS
ERROR RECOVERY ............ .
THEORY OF OPERATION
OVERALL SYSTEM BLOCK DIAGRAM
Omnibus to RX8E Interface Signals
Unibus
to RXII Interface Signals
Interface to pCPU Controller Signals
pCPU Controller
to Read/Write Electronics Signals
Read/Write Electronics to Drive Signals .....
DETAILED BLOCK DIAGRAM AND LOGIC DISCUSSION
RX8E Interface
Device Select and lOT Decoder
Interrupt Control and Skip Logic
C Line Select Logic
..... .
Interface Register
...... .
Sequence and Function Control Logic
RX11 Interface
Address Decoder
DataPath Selection
Interface Register
Sequence and Function Control Logic
Interrupt Control Logic
...... .
Vector Address Generator
..... .
Microprogrammed Controller (PCPU) Hardware
Control
ROM and Memory Buffer ..
Program Counter and Field Counter
Instruction Decode Logic
..... .
Do Pulse Generator
........ .
Branch Condition Selector and Control
Scratch Pad Address Register and Scratch Pad
Counter
Input Selector, Counter, and Shift Register
pCPU Timing Generator .....
Sector Buffer and Address Register
CRC Generator and Checker
..
Data Synchronizer and Separator
Output Circuit ....... .
Microprogram Instruction Repertoire
DO Instruction ..
Conditional Branch
Wait Branch
v
Page
4-9
4-9
4-9
· 4-10
· 4-10
· 4-10
· 4-10
· 4-15
· 4-16
5-1
5-2
5-3
54
5-6
5-7
5-8
5-8
5-8
5-8
5-8
· 5-10
· 5-10
· 5-11
· 5-11
· 5-13
· 5-13
· 5-13
· 5-14
· 5-14
· 5-14
· 5-14
· 5-16
· 5.;16
· 5-17
· 5-17
· 5-17
· 5-17
· 5-18
· 5-18
· 5-18
· 5-19
· 5-20
· 5-21
· 5-21
· 5-22
· 5-22

5.2.4.4
5;2.4.5
5.2.5
5.2.6
5.2.6.1
5.2.6.2
5.2.6.3
5.2.6.4
5.2.7
S.2.7.1
5.2.7.2
5.2.7.3
5.2.7.4
CHAPTER 6
6.1
6.2
6.3
6.3.1
6.3.2
6.4
6.4.1
6.4.1.1
6.4.1.2
6.4.2
FigUre No.
1.1
1-2
1·3
1·4
1-S
1·6
1·7
1·8
1·9
1·10
1·11
2·1
2·2
2-3
2-4
2·5
2·6
CONTENTS (Cont)
Page
Open Scratch Pad ................................ 5.22
Jump
....................................... 5.23
Microprogram Flowchart Description ......................... 5.23
Read/Write Electronics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.36
Diskette Position . . . .
.'. . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.36
Head Read/Write Circuitry ..•... : ..................... 5.36
Head Load Control and Solenoid Drivers .................... 5.36
Stepper Motor Control and Motor Drivers ............•....... 5.36
Mechanical Drive ..................................•. 5.38
Drive Mechanism ................................. 5.39
Spindle Mechanism . . . . . . . . . . . . . .. . . . . . . . . . .. . . .. . . 5.39
POsitioning Mechanism ............................... 5.39
Head Load Mechal1ism ... ; ...............•.......... 541
MAINtENANCE .
RECOMMENDED TOOLS AND TEST EQUIPMENT .................... 6.1
CUSTOMER CARE ..................................... 6.1
REMOVAL AND REPLACEMENT ............................. 6.2
Module Replacement . . . . . . . . . . . . : . . . . . . . " . . . . . . . . . . . . .
Drive Placement ................................... .
CORRECTIVE MAINTENANCE •.............................
Initialize Errors
10 • • ~ • • • • • • • • • • • • II • • • • • • II • • • • • • • • • • • •
Interface Diagnostic in Memory ....................•....
Diagnostics Not in Memory .......................... .
KM11 Usage ......... ' ......................... ; .. .
ILLUSTRA nONS
6·2
64
6-4
6·4
64
6·9
6·9
Title Page
Floppy Disk System Configuration ................•............ 1.2
Front View ofthe Floppy Disk System ............... '. . . . . . . . . . .. 1.3
M83S7 Module (RX8E Interface) .............................. 14
M7846 Module (RXll Interface) .............................. 1.5
Top View ofthe RXOI ......... . . . . . . . . . . . . . . . . . . . . . . . . . •. 1.6
Underside View of Drive ................................... 1.7
Top View of Drive ...................................... 1-8
Diskette Media ........... '. . . . '. . . . . . . . . . . . . . • . . . . . . . . .. 1.9
Flux Reversal Patterns . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . 1.10
Track Format (Each Track) ................................. 1.10
Sector Format (Each Sector) ..........................•...... 1.11
RXOI ••...............•...•...................... 2.2
Cabinet Layout Dimensions ................................. 2.3
RXOl Shipping Restraints ...........•...................... 2.5
RX8/RXll Unpacking .......•.............. '. . . . . . . . . . . . .. 2.7
RXOI Cabinet Mounting Information ............................ 2-8
Cable Routing, BC05L·15 .................................. 2.9
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Figure No.
2·7
3·1
3·2
3·3
34
3·5
3·6
.3·7
3·8
4·1
4·2
4·3
4-4
4-5
4-6
4·7
4-8
4·9
4·10
5·1
5·2
5·3
54
5·5
5·6
5·7
5-8
5·9
5·10
5·11
5·12
5·13
5·14
5·15
5·16
5.17
5·18
5·19
5·20
5·21
5·22
5·23
5·24
5·25
5·26
6·1
6-2
6·3
ILLUS'tRA nONS (Cont) .
Title .
PlJge
Flexible Diskette Insertion . . . . . . . . . . . . . . . . . . . . . . . . . . • . 2·11
RXCS Fonnat (RXll) ................. . .. ~ • • .. • . • . • . 3·2
RXTA Format (RX1l) .. .. .. .. .. .. .. .. .. .. . .... 3.3
RXSA Format (RXll) . . . . . . . . . . . . .... ,. . . . . • . • .. 3·3
RXDB Fonnat (RXU) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . • . . . . •. 34·
RXES Fonnat (RXl1) ..........•.................... "/ • . .. 34
RXl 1Write/Write Deleted Data/Read Example ..... . . . . • • . . . .• .. 3·9
RXII Empty Buffer Example ...........•..............•• ; .•. 3~1O
RXII Fill Buffer Example ...........................• i'. ; •• '. 3-13
LCD Word Fonnat (RX8E) ......................•...••....• 4·2
Command Register Fonnat (RX8E) ., .... ,....................... 4·3
Error Code Register Fonnat .........•.......•... ~ . . . . . . . . • 44
RXTA Format (RX8E) ........... " ..•.. , . . . . • • . . . •. • . . . .4·5
RXSA Format (RX8E) . . . . , . . . . . . . . . . . . . . • . . . . . . • . • .4·5
RXDB Fonnat (RX8E) ......................................... 4·6'
RXES Fonnat (RX8E) .......................•.......•... , 4-6
RX8E Write/Write Deleted Data/Read Example .............•.••.•.... 4·11 .
RX8E Empty Buffer Example ................•...•........ , .. 4.13
Fill Buffer Example ..................•........ , .........• 4·14
Bus Structure ......................................., 5·1
Omnibus to RX8E Interface Signals ..............•...•.......... 5·2
Unibus to RXll Interface Signals . . . . . . • . . . . . • . • . . . • . . . .. 5·3
Interface to J.lCPU Controller Signals ............. , ...•.....• , .. , .54
J.lCPU Controller to Read/Write Electronics Signals .............,...,... S-6
Read/Write Electronics to Drive Signals .....•..•... ,. • . . • . . . • . • . .. 5·7
RX8E Interface Block Diagram . . . . . . . . . . • .. . • . . .. . . • • . . . •. 5·9'
RXl1 Interface Block Diagram ...............• , ...... ' ..... 5·12
J.lCPU Controller Block Diagram ......... , .............. , ... 5·15
Data and Clock Separation ..................•..•.....•...•.. 5·19
ID Address Mark Data Separation .......•........•...•........ '. 5.20
Initialize and Function Decode Flowchart ........•.. , .......•...... 5·24
Empty and Fill Buffer Functions Flowchart ...........••...........• 5.25
Read Sector and Read Status Functions Flowchart ..••..•..•..• 5·26
Write Sector Function Flowchart ....................,.....,... 5·28
FINDTR Subroutine Flowchart ..........................,.... 5·29
FINDHD and GETDAM Subroutines Flowchart ..................... .. 5·30
HDRCOM, BDSRT, BADHDRRoutines Flowchart ...••.. , .•...• '., .... 5.32
DELAY, FINDSE,
WRTOS, GETWRD Subroutines Flowchart ... , ........... 5~33
STEPHD. WAITRN, MAGCOM Subroutines Flowchart ...........•..••• .. 5·34
DIFand CHKRDY Subroutine Flowchart ............• . .....• , .. 5·35
Read/Write Electronics Block Diagram . . . . . . . . . . • . . . . . , . . • . . . . . . . . 5·37
Disk Drive Mechanical System .................•.....•... ; .... 5·38
Drive Mechanism ...................................,... $-39
Centering Cone and Drive Hub ...........................•.... 5-40
PositiOning Mechanism ., . . . . . . . . . . . . . . . . . . . . . . .. .. . . . . . • . . 540
RXOI. Rear View ..............•............•. ,........... 6·2
Troubleshooting Flow ......... . . . . . . . . . .. . . ; . . . . • .. 6-5
BC05L-15 Cable ....•......................•...•... ~ . •. 6·7

Figure No.
: .. ,
6,.4
6-5
6-6
6-7
Table No.
ILLl~STRATIONS (Coot)
RX8 Status Routine
RXll Status Routine
Title
, KM 11 Maintenance Module Inserted ..
KMll Light and Switch Definitions for RXOI
TABLES
Title
Interface Code/Jumper Configuration .
Device Code Switch Selection .....
CLine Transfer Control Signals
Recommended Tools and Test Equipment
M7727 Connectors
............ .
viii
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Page
· 6-10
· 6-10
· 6-11
........ 6-12
Page
. 2-10
.. 4-1
. 5-10
6-1
. .. .. 6-3
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CHAPTER 1
GENERAL INFORMATION
This manual presents information on the installation, operation, programming,·theory of operation, and
maintenance
of the RX8 or RX11 Floppy Disk System. Chapter 2 (Installation and Operation) should be consulted
for unpacking and installation information. Chapter 2 also provides information on the proper care
ofthe media and
should be read carefully. .
1.1 INTRODUCTION
The RX8 and RXll Floppy Disk Systems consist of an RX01 subsystem and either an RX8E interface for a PDP-8
system or an
RX11 interface for a PDP-II system.
The
RX01 is a low cost, random access, mass memory device that stores data in ftxedlength blocks on a
preformatted, IBM-compatible, flexible diskette. Each drive can store and retrieve up
to 256K 8-bit bytes of data
(pDP-ll or PDP-8) or 128K 12-bit words (PDP-8). The
RX01 consists of one or two flexible disk drives, a single
read/write electronics module, a microprogrammed controller module, and a power supply, enclosed in a
rack-mountable, 10-1/2 inch, self-cooled chassis. A cable
is included for connection to either a PDP-8 interface
module for
use. on the PDP-8 Omnibus or a PDP-II interface for use on the PDP-II Unibus.
The
RX01 performs implied seeks. Given an absolute sector address, the RX01 locates the desired sector and
performs the indicated function, including automatic head position veriftcation and hardware calculation and
veriftcation of the Cyclic Redundancy Check (CRC) character. The
CRC character that is read and generated is
compatible with IBM 3740 equipment.
The
RXOI connects to the M8357 Omnibus interface module, which converts the RX01 I/O bus to aPDP-8 family
omnibus structure. It controls interrupts to the CPU initiated by the RXOl, controls data interchange between the
RXOland the host
CPU, and handles I/O transfers used to test status conditions.
The
RXOl connects to the M7846 Unibus interface module, which converts the RX01 I/O bus to aPDP-ll Unibus
structure.
It controls interrupts to the CPU initiated by the RX01, decodes Unibus addresses for register selection,
and handles data interchange between the
RXOI and the host CPU.
The interface modules are dc powered by their host processor.
1.2 PHYSICAL DESCRIPTION
Acomplete system consists of the follOwing components:
M7726 controller module
M7727 read/write dectronics module
H771A or B power supply
RXOl-CA floppy disk drive (60Hz, max of 2)
RXOl-CC floppy disk drive (50 Hz, max of 2)
M8357 (RX8E) or M7846 (RX11) interfaces
1-1·

All components except the interface are housed in a 10-1/2 in. rack-mountable box. The power supply, M7726
module, and M7727 module are"mounted above the drives. Interconnection from the
RXOI to the interface is with a
40-conductor BC05L-15 cable
of standard length (15 ft). Figure 1-1 is a configurationdrawing of the system, and
Figure
1-2 is a front view of a dual drive system.
DRIVE#O
DRIVE
ELECTRONICS
M7727
DRIVE #1
1.2.1 RX8E/RXll Interfaces
o DISKETTE
,.CPU
CONTROLLER
M7726
Figure 1·1 Floppy Disk System Configuration
MB357
OMNIBUS
INTERFACE
M7846
UNIBUS
INTERFACE
o
M
N
I
B
U
S.
U.
N
I
B
U
S
CP-1505
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Interface modules M8357 (RX8E) and M7846(RXll) are both quad modules. The M8357 plugs into an Omnibus (
slot and allows the RXOl to
be" used on the PDP-8 processors. The M7846 plugs into an· SPC (small peripheral
controller) slot with any
PDP-II processor. Figure 1-3· shows the M8357 module and its major sections. Figure 14
shows the M7846 module and its major sections.
1.2.2 Micl"oprogrammed Controller . .
The M7726 microprogrammed controller module is located in the RXOI cabinet as shown in Figure 1-5. The M7726
is hinged on the left side and lifts up for access to the M7727 read/write electronics module.
1.2.3 Read/Write Electronics
The M7727 read/write electronics module
is located in the RX01 cabinet as shown in Figure 1-5.
1.2.4 Electro,Mechanical Drive
A maximum
of two drives can be attached to the read/write electronics. The electro-mechanical drives are mounted
side
by side under the read/write electronics board (M7727). Figure 1-6, which is an underside view of the drive,
shows the drive motor connected
to the spindle by a belt. (This belt and the small pulley are different on the 50 Hz (
and 60 Hz units; see Paragraph 2.2.3.2 for complete input power modification requirements.) Figure 1-7 is the top \.. .
.
view showing the electro-mechanical components of the drive.
1-2

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7408-1
Figure 1-2 Front View of the Floppy Disk System
1.2.5 Power Supply
The
H771 power supply is mounted at the rear of the RX01 cabinet as shown in Figure 1-5. The H771A is rated at
60 Hz ± 1/2 Hz over avoltage range of 90-132 Vac. The H771C and D are rated at 50 Hz ± 1/2 Hz over four voltage
ranges:
90-120 Vac }
100-132 Vac 3.5 Acircuit breaker; H771C
180-240 Vac }
200-264 Vac 1.75 Acircuit breaker; H77lD
Two power harnesses are provided to adapt the H771C or D to each voltage range. This is not applicable to the
H771A.
See Paragraph 2.2.3.2 for complete input power modification requirements.
1.3 SYSTEMS COMPATIBILITY
This section describes the physical, electrical, and logical aspects of IBM compatibility as defmed for data
interchange with
IBM system 3740 devices.
1.3.1
Media
The media used on the RX8 or RX11 Floppy Disk System is compatible with the IBM 3740 family of equipment
and
is shown in Figure 1-8.
The "diskette" media was designed by applying tape technology to disk architecture. This resulted in a flexible
oxide-on-mylar surface encased in a plastic envelope with a hole for the read/write head, a hole
for the drive spindle
hub, and a hole for the hard index mark.
The envelope is lined with a fiber material that cleans the diskette surface.
The media is supplied to the customer preformatted and pretested.
1-3

BC05L-15
INTERFACE
CABLE
CONNECTOR
DEVICE
CODE
SWITCHES
Figure 1-3 M8357 Module (RX8E Interface)
1-4
7408-3
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PRIORITY
PLUG
CONNECTOR
FOR THE
BC05L·15
INTERFACE
CABLE
RX11
INTERFACE
REGISTER
Figure 14 M7846 Module (RX11 Interface)
1·5
7408·4

M7727
READIWRITE
ELECTRONICS
MODULE
Figure 1-5 Top View of the RXOl
1-6
M7726~CPU
CONTROLLER
MODULE
BC05L-15
INTERFACE
CABLE H771
POWER
SUPPLY
7408-8
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AC
POWER
CONNECTOR
DC
STEPPER
MOTOR
DRIVE MOTOR
Figure 1-6 Underside View of Drive
1·7
DRIVE SPI NDLE
PULLEY
7408-5

READ/WRITE
HEAD
HEAD LOAD
ARM
HELIX
DRIVE
Figure 1-7 TopView of Drive
1-8
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REGISTRATION
INDEX HOLE HOLE
READ/WRITE
HEAD
APERTURE
Figure 1-8 Diskette Media
1·9
7408-2

1.3.2 Recording Scheme
The recording scheme used
is "double frequency." In this method, data is recorded between bits of a constant clock
stream. The clock stream consists
of a continuous pattern of 1 flux reversal every 4ps (Figure 1-9). A data "one" is
indicated by an additional reversal between clocks (i.e., doubling the bit stream frequency; hence the name). A data
''zero''is indicated by no flux reversal between clocks.
A continuous stream
of ones, shown in the bottom waveform in Figure 1-9, would appear as a "2F" bit stream, and
a continuous stream of zeros,.shown in the top waveform in Figure 1-9, would appear as a "IF" or fundamental
frequency bit stream.
ALL ZEROS
PATTERN
0 0 0 0 0 0 0 0 0
CHANGING
PATTERN
0 0 0 0 0 0 0
ALL ONES
PATTERN
I I
I I
I I
""4 4~.e<
...
CP-1506
I
Figure 1-9
Flux Reversal Patterns
1.3.3 Logical Foimat
The logical format
of the RX8 and RX11 Floppy Disk Systems is the same as that used in the IBM 3740.
Data is recordt;:d on only one side
of the diskette. This surface is divided into 77 concentric circles or "tracks"
numbered 0-76. Each track is divided into 26 sectors numbered 1-26 (Figure 1-10). Each sector contains two
major fields: the header field and the data field (Figure 1-11).
LL.E.D. TRANSDUCER OUTPUT
'---H~A~R 0:1-"1
{',..., .--_-' I~X~~ L------------...--'----111
SECTOR
#26
PRE-INDEX
GAP
SECTOR
01320 BYT ES
#1
T
SOFT INDEX MARK
1 BYTE
.--- ROTATION
SECTOR SECTOR
#2 #3
Figure l-lD Track Format (Each Track)
SECTOR
#4
t
CP-1507
1.3.3.1 Header Description -The header field is broken into seven bytes (eight bits/byte) of information and is
preceded by a field of zeros for synchronization.
1. Byte No'. 1: ID Address Mark -This is a unique strellill of flux reversals (not a string of data bits) that is
decoded by the controller to identify the beginning of the header field.
2. Byte No.2: Track Address -This is the absolute (0-1148) binary track address. Each sector contains
track address information to identify its location on 1 of the 77 tracks.
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