DEC LA 120 User manual

EK-LA120- TM-001
LA120
TECH N ICAl MAN UAl
digital equipment corporation • maynard, massachusetts

Copyright © 1980 by Digital Equipment Corporation
All Rights Reserved
The material in this manual is for informational
purposes
and is subject to change without notice.
Digital
Equipment Corporation assumes no re-
sponsibility for any errors which may appear in
this
manual.
Printed in U.S.A.
This document was set on DIGITAL's DECset-8000
computerized typesetting system.
First Edition, January 1980
The following are trademarks of Digital Equipment Corporation,
Maynard, Massachusetts:
DIGITAL
DEC
PDP
DECUS
UNIBUS
oECsystem-l0
DECSYSTEM-20
DIBOL
EDUSYSTEM
VAX
VMS
MASSBUS
OMNIBUS
OS/8
RSTS
RSX
lAS

CHAPTER t
1.1
1.2
1.2.1
1.2.2
1.2.3
1.2.4
1.2.5
1.2.6
1.2.7
1.2.8
1.2.9
1.2.10
1.2.11
1.3
1.4
CHAPTER 2
2.1
2.1.1
2.1.2
2.1.3
2.1.4
2.2
2.2.1
2.2.1.1
2.2.1.2
2.2.1.3
2.2.1.4
2.2.1.5
2.2.1.6
2.2.1.7
2.2.1.8
2.2.1.9
2.2.1.10
2.2.1.11
2.2.1.12
2.2.1.13
2.2.1.14
2.2.2
2.2.2.1
2.2.2.2
2.2.3
2.2.4
2.2.5
2.3
CONTENTS
Page
OPERATORS INFORMATION
INTRODUCTION .............................................................................................. 1-1
OPERATOR'S CONSOLE .................................................................................. 1-2
Lights........................................................................................................... 1-2
Local Control Keys ...................................................................................... 1-4
SET-UP Keys............................................................................................... 1-4
Control Character Keys................................................................................ 1-5
Other Keys ................................................................................................... 1-6
Optional Numeric Keypad ........................................................................... 1-6
Power ON /OFF Switch and Voltage Selector Switch.................................... 1-6
Cover Interlock Switch ................................................................................. 1-8
Paper Adjust Knob ....................................................................................... 1-8
Tractor Adjust Knobs .................................................................................. 1-9
Carriage Adjustment Lever........................................................................... 1-9
ALARM INDICATORS ...................................................................................1-10
OPERATOR TESTING AND TROU BLESHOOTING ................................... 1-11
INSTALLATION, INTERFACE, AND SPECIFICATIONS
INSTALLATION AND CONFIGURATION .................................................... 2-1
Unpacking and Inspection............................................................................2-2
Packing Procedures ......................................................................................2-2
Checkout Procedure.....................................................................................2-5
Answerback
Jumper .....................................................................................2-6
INTERFACE INFORMATION .........................................................................2-8
Interface Signals...........................................................................................2-8
Protective Ground ................................................................................2-8
Transmitted Data (TDX) ......................................................................2-8
Received
Data (RDX) ..........................................................................2-8
Request to Send
(RTS) .........................................................................2-9
Clear to Send (CTS)..............................................................................2-9
Data Set Ready ....................................................................................2-9
Signal Ground ......................................................................................2-9
Carrier Detect (RLSD) ..........................................................................2-9
Secondary Request
to Send (SRTS) ......................................................2-9
Speed Indicator (SPDI) ........................................................................2-9
Secondary
Carrier Detect (SRLSD) ......................................................2-9
Data Terminal Ready (DTR) ................................................................2-9
Ring
Indicator (RI) ..............................................................................2-9
Speed Select (SPDS) .............................................................................2-9
EIA Interface Cables ....................................................................................2-9
BC22A-I0, -25 ....................................................................................2-10
BC22B-I0, -25 ....................................................................................
2-1 0
Impedance of Terminator ...........................................................................2-10
Rise and Fall Times .................................................................................... 2-1 0
Open Circuit Voltage..................................................................................2-10
LA120 SPECIFICATIONS ................................................................................2-10
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
3.2.2.S
3.2.2.6
3.2.2.7
3.2.2.8
3.2.2.9
3.2.2.10
3.2.2.11
3.2.2.12
3.3
3.3.1
3.3.2
3.3.3
3.3.4
3.3.S
3.3.6
3.3.7
3.3.8
3.3.9
3.3.10
3.3.11
3.3.12
3.3.13
3.3.14
3.3.15
3.3.16
3.3.17
3.4
3.5
3.6
3.6.1
3.6.2
3.6.2.1
3.6.2.2
3.7
3.7.1
3.7.2
3.7.3
3.7.4
CONTENTS (Coot)
Page
PROGRAMMER'S INFORMATION
GENERAL.......................................................................................................... 3-1
ESCAPE SEQUENCES....................................................................................... 3-2
Parser Program ............................................................................................ 3-2
Sequence Descriptions.................................................................................. 3-2
Printer Character Sets........................................................................... 3-S
Active Position ..................................................................................... 3-6
Linefeed-Newline Mode ....................................................................... 3-7
Horizontal Pitch................................................................................... 3-7
Horizontal Margins.............................................................................. 3-8
Horizontal Tabs ................................................................................... 3-8
Vertical Pitch........................................................................................ 3-8
Form Length ........................................................................................ 3-8
Vertical Margins................................................................................... 3-8
Vertical Tabs ........................................................................................ 3-9
Product Identification .......................................................................... 3-9
Alternate Keypad Mode ....................................................................... 3-9
CONTROL CHARACTERS............................................................................. 3-10
Null or Delete (NULL or DEL) .................................................................. 3-10
End of Text (ETX)......................................................................................3-10
End of Transmission (EaT) ........................................................................ 3-1 0
Enquiry (ENQ)........................................................................................... 3-10
Bell (BEL) .................................................................................................. 3-11
Backspace (BS) ........................................................................................... 3-11
Horizontal Tab (HT) .................................................................................. 3-11
Line Feed (LF) ........................................................................................... 3-\\
Vertical Tab (VT) ....................................................................................... 3-\\
Form Feed (FF)..........................................................................................3-\1
Carriage Return (CR).................................................................................3-\1
Shift In (SI)................................................................................................. 3-\\
Shift Out (Sa) ............................................................................................. 3-\\
Data Link Escape (OLE) ............................................................................3-\1
Cancel (CAN).............................................................................................3-1\
Substitute
(SU B) .........................................................................................3-\1
Escape (ESC)..............................................................................................3-\2
APL CHARACTER SET................................................................................... 3-12
SAMPLE FORM SETUP USING ESCAPE SEQUENCES .............................. 3-13
SYNCHRON IZATION ....................................................................................3-\3
Synchronization Limits....................................................:..........................3-\5
Fill Time Formulas.....................................................................................
3-15
Horizontal Movement ........................................................................3-\S
Vertical Movement .............................................................................3-\5
KEYBOARD OPERATION .............................................................................3-\6
Auto Repeat ...............................................................................................3-\6
Printable Character Keys............................................................................3-\6
Control Character Keys ..............................................................................
3-17
CTRL (Control) Key ..................................................................................3-\7
iv

3.7.5
3.7.6
3.7.7
CHAPTER 4
4.1
4.1.1
4.1.2
4.1.2.1
4.1.2.2
4.1.3
4.1.4
4.1.5
4.1.6
4.1.6.1
4.1.6.2
4.1.6.3
4.1.7
4.1.7.1
4.1.7.2
4.1.8
4.1.9
4.1.10
4.1.11
4.2
4.2.1
4.2.2
4.2.3
4.2.4
4.2.5
4.2.6
4.2.7
4.2.8
4.3
4.3.1
4.3.2
4.3.3
4.4
4.4.1
4.4.2
4.4.3
4.5
4.5.1
4.5.2
4.5.3
4.5.4
4.6
4.6.1
CONTENTS (Cont)
Page
Optional Auxiliary Keypad.........................................................................3-18
BREAK Key ...........:..................................................................................3-18
VIEW Key..................................................................................................3-18
LA120 THEORY OF OPERATION
BASIC SYSTEM CONFIGURATION ............................................................... 4-1
Microprocessor ............................................................................................ 4-1
Device Addressing........................................................................................ 4-1
Memory Space ..................................................................................... 4-3
I/O Space............................................................................................. 4-3
Interrupts..................................................................................................... 4-3
ROM ...........................................................................................................4-4
RAM ........................................................................................................... 4-5
Keyboard.....................................................................................................4-5
Keyboard Addressing...........................................................................4-5
Switch Matrix.......................................................................................4-7
Separately Decoded Keys .....................................................................4-7
Display.........................................................................................................4-7
LEDs ...................................................................................................4-7
Seven Segment Display.........................................................................4-7
Non-Volatile Memory..................................................................................4-8
DC305 Printer Controller.............................................................................4-9
8251A
USART .............................................................................................4-9
Utility I/O Ports.........................................................................................4-10
DC305
PRINTER CONTROLLER ...................................................................4-10
Dot Print Control....................................................................................... 4-1 0
Carriage Position Count ............................................................................. 4-11
Carriage Speed Control .............................................................................. 4-11
Line Feed Control ...................................................................................... 4-11
Bell Control ................................................................................................ 4-11
Frequency Generation................................................................................ 4-11
Tick Alarm................................................................................................. 4-11
Interrupt Vectors........................................................................................4-12
LA
120 FIRMWARE OVERViEW ....................................................................4-12
Scheduling..................................................................................................4-12
ROM Layout..............................................................................................4-12
RAM Layout..............................................................................................4-13
PRINT CONTROL FIRMW ARE .....................................................................4-13
Starting the Printing Operation...................................................................4-13
Flight Time Compensation .........................................................................4-15
Dot Rate Limiting ......................................................................................4-15
CARRIAG E SERVO FIRMWARE ..................................................................4-16
Transitions .................................................................................................4-16
Reading the Position
Counter .....................................................................4-16
Carriage Speed
Command ..........................................................................4-16
Error Conditions........................................................................................4-16
COMMUNICATION FIRMWARE .................................................................4-17
Communication Modes ..............................................................................4-17
v

4.6.2
4.6.3
4.6.4
4.6.5
4.6.5.1
4.6.5.2
4.6.5.3
4.6.5.4
4.6.6
4.6.6.1
4.6.6.2
4.6.6.3
4.6.6.4
4.6.6.5
4.6.6.6
4.6.7
, 4.6.7.1
4.6.7.2
4.6.8
4.6.8.1
4.6.8.2
4.6.8.3
4.6.9
4.7
4.7.1
4.7.1.1
4.7.1.2
4.7.1.3
4.7.1.4
4.7.1.5
4.7.1.6
4.7.1.7
4.7.2
4.7.3
4.7.3.1
4.7.3.2
4.7.3.3
4.7.4
4.7.5
4.7.6
4.8
4.8.1
4.8.1.1
4.8.1.2
4.8.2
4.8.3
4.9
4.9.1
4.9.2
4.9.3
4.9.4
CONTENTS (Cont)
Page
Local Mode ................................................................................................4-17
Disconnects................................................................................................4-17
Full Duplex Without EIA Controls.............................................................4-17
Full Duplex with EIA Controls...................................................................4-17
Full-Duplex Break..............................................................................4-18
Full-Duplex Disconnect......................................................................4-18
Restraint
Mode ..................................................................................4-19
Speed Control Mode ...........................................................................4-19
Half Duplex................................................................................................4-19
Initial Direction Determination ..........................................................4-19
Reverse Channel.................................................................................4-19
Request to Send Delay........................................................................4-19
Turnaround Characters ......................................................................4-20
Half-Duplex Break .............................................................................4-20
Half-Duplex Disconnect.....................................................................4-20
Communication State Control ................................................................... .4-21
Communication State Table .........................................,.................... .4-21
Communication Handler.................................................................... 4-21
Control Code Generation and Detection.....................................................4-23
Input Scanning ...................................................................................4-23
Transmit Scanning..............................................................................4-23
Control Code Generation ...................................................................4-23
Functional State Diagrams .........................................................................4-23
ESCAPE SEQUENCE PROCESSING ..............................................................4-28
Escape Sequence StateTransition Table......................................................4-28
Element No. 1.....................................................................................4-29
Element
No. 2.....................................................................................4-30
Element No. 3.....................................................................................4-30
Element No. 4.....................................................................................4-30
Element No. 5.....................................................................................4-30
Element No. 6..................................................................................... 4-31
Element No. 7..................................................................................... 4-31
Escape Sequence Jump Table...................................................................... 4-31
Escape Sequence Parser .............................................................................. 4-31
Begin Parsing...................................................................................... 4-31
Initialize Parser...................................................................................4-32
Flow Controller..................................................................................4-32
CSI Parameters...........................................................................................4-33
Control Strings...........................................................................................4-33
Final Character Perform-Function Routines...............................................4-33
SET-UP COMMAND PROCESSING ..............................................................4-33
SET-UP Command Implementation...........................................................4-34
Multiple Choice
SET-UP Commands .................................................4-34
Immediate Action SET-UP Commands ..............................................4-34
SET-UP Handler ........................................................................................4-35
SET-UP/Keyboard Handler Relationship..................................................4-36
CHARACTER PROCESSING .........................................................................4-36
Character Reception...................................................................................4-36
Background Executive................................................................................4-36
Print Line Builder.......................................................................................4-37
Answerback Entry Handler ........................................................................4-38
vi

CHAPTERS
5.1
5.2
5.3
5.4
5.5
5.6
5.7
5.8
5.9
5.10
CHAPTER 6
6.1
6.2
6.2.1
6.2.2
6.3
6.3.1
6.3.2
6.4
6.4.1
6.4.2
6.5
6.5.1
6.5.2
6.6
6.6.1
6.6.2
6.7
6.7.1
6.7.2
6.8
6.8.1
6.8.2
6.9
6.9.1
6.9.2
6.10
6.10.1
6.10.2
6.11
6.11.1
6.11.2
6.12
6.12.1
6.12.2
6.13
6.13.1
CONTENTS (Coot)
Page
TROUBLESHOOTING THE LA120
GENERAL .......................................................................................................... 5-1
DC SERVO TEST ............................................................................................... 5-8
ENCODER DUTY CYCLE CHECK/ADJUSTMENT .....................................5-9
CLOCK TEST ...................................................................................................5-12
WAKE UP TEST ...............................................................................................5-12
PRINT CHARACTER TEST ............................................................................5-14
USART TEST ....................................................................................................5-17
KEYBOARD TEST ........................................................................................... 5-21
LINE FEED TEST ............................................................................................5-24
BELL
TEST .......................................................................................................5-27
LA120 SUBASSEMBLY REMOVAL AND INSTALLATION
GENERAL .......................................................................................................... 6-1
PRINTER HOUSING ........................................................................................ 6-1
Printer Housing Removal............................................................................. 6-1
Printer Housing Installation ......................................................................... 6-3
PRINT HEAD ASSEMBLY ............................................................................... 6-3
Print Head Assembly Removal .....................................................................6-4
Print Head Assembly Installation .................................................................6-4
PRINT HEAD CABLE ....................................................................................... 6-5
Print Head Cable Removal ........................................................................... 6-5
Print Head Cable Installation ....................................................................... 6-5
TIMING BELT...................................................................................................6-6
Timing Belt RemovaL...................................................................................6-6
Timing Belt Installation................................................................................6-6
PRINT BAR ........................................................................................................ 6-8
Print Bar RemovaL....................................................................................... 6-8
Print Bar Installation.................................................................................... 6-8
CARRIAGE ASSEMBLY AND FRONT CARRIAGE SHAFT ........................6-9
Carriage Assembly and Front Carriage Shaft Removal .................................6-9
Carriage Assembly and Front Carriage Shaft Installation ........................... 6-11
CARRIAGE ECCENTRIC BEARING AND LEVER ..................................... 6-11
Carriage Eccentric Bearing and Lever Removal .......................................... 6-11
Carriage Eccentric Bearing and Lever Installation....................................... 6-11
REAR CARRIAGE SHAFT AND PLAIN BUSHING ....................................6-13
Rear Carriage Shaft and Plain Bushing Removal ........................................6-13
Rear Carriage Shaft and Plain Bushing Installation.....................................6-14
RIBBON DRIVE PULLEY ...............................................................................6-14
Ribbon Drive Pulley Removal ....................................................................6-14
Ribbon Drive Pulley Installation ................................................................6-14
RIBBON DRIVE ASSEMBLy ..........................................................................6-15
Ribbon Drive Assembly Removal...............................................................6-15
Ribbon Drive Assembly Installation...........................................................6-17
RIBBON DRIVE FAFNIR BEARING .............................................................6-18
Ribbon Drive Fafnir Bearing Removal .......................................................6-18
Ribbon Drive Fafnir Bearing Installation ...................................................6-18
RIBBON ECCENTRIC AND BACKSTOP SPRING .......................................6-19
Ribbon Eccentric and Backstop Spring Removal ........................................6-19
vii

6.13.2
6.14
6.14.1
6.14.2
6.15
6.15.1
6.15.2
6.16
6.16.1
6.16.2
6.17
6.17.1
6.17.2
6.18
6.18.1
6.18.2
6.19
6.19.1
6.19.2
6.20
6.20.1
6.20.2
6.21
6.21.1
6.21.2
6.22
6.22.1
6.22.2
6.23
6.23.1
6.23.2
6.24
6.24.1
6.24.2
6.25
6.25.1
6.25.2
6.26
6.26.1
6.26.2
CHAPTER 7
7.1
7.2
7.3
7.4
7.5
7.6
CONTENTS (Cont)
Page
Ribbon Eccentric and Backstop Spring Installation .................................... 6-20
DC MOTOR AND ENCODER ASSEMBLY ................................................... 6-20
DC Motor and Encoder Assembly Removal ............................................... 6-20
DC Motor and Encoder Assembly Installation ........................................... 6-21
TRACTOR DRIVE SHAFTS AND TRACTOR ASSEMBLIES ...................... 6-22
Tractor Drive Shaft and Tractor Assembly Removal................................... 6-22
Tractor Drive Shaft and Tractor Assembly Installation............................... 6-23
IDLER GEAR ASSEMBLy.............................................................................. 6-24
Idler Gear Assembly Removal .................................................................... 6-24
Idler Gear Assembly Installation ................................................................ 6-24
STEPPING MOTOR ASSEMBLY.................................................................... 6-25
Stepping Motor Assembly Removal............................................................ 6-25
Stepping Motor Assembly Installation........................................................ 6-26
RIBBON CHASSIS ASSEMBLY ...................................................................... 6-27
Ribbon Chassis Assembly Removal ............................................................ 6-27
Ribbon Chassis Assembly Installation ........................................................ 6-28
RIBBON SPOOL RATCHET WHEELS AND FRICTION DISKS.................. 6-29
Ribbon Spool Ratchet Wheel(s) and Friction Disk Removal....................... 6-29
Ribbon Spool Ratchet Wheel(s) and Friction Disk Installation ................... 6-30
KEYBOARD/NUMERIC PAD ASSEMBLY .................................................. 6-30
Keyboard/Numeric Pad Assembly Removal .............................................. 6-30
Keyboard/Numeric Pad Assembly Installation........................................... 6-31
POWER SUPPLY ASSEMBLY ........................................................................ 6-32
Power Supply Assembly Removal ............................................................... 6-33
Power Supply Assembly Installation ........................................................... 6-34
PRINTER MECHANISM ASSEMBLY ........................................................... 6-35
Printer Mechanism Assembly Removal....................................................... 6-35
Printer Mechanism Assembly Installation................................................... 6-35
CVT POWER SUPPLY MODULE................................................................... 6-38
CVT Power Supply Module Removal ......................................................... 6-38
CVT Power Supply Module Installation ..................................................... 6-39
POWER ENTRY BRACKET ASSEM'BLY ...................................................... 6-39
Power Entry Bracket Assembly Removal .................................................... 6-40
Power Entry Bracket Assembly Installation ................................................ 6-40
FAN .................................................................................................................. 6-40
Fan Removal.............................................................................................. 6-40
Fan Installation.......................................................................................... 6-40
LOGIC/POWER BOARD ................................................... ~ ............................ 6-41
Logic/Power Board Removal ..................................................................... 6-41
Logic/Power Board Installation ................................................................. 6-42
ADJUSTMENT PROCEDURES AND LUBRICATION
PRINT HEAD ADJUSTMENT..........................................................................
7-1
PRINTER MECHANISM ADJUSTMENT ....................................................... 7-1
PAPER GUIDE ADJUSTMENT ....................................................................... 7-4
PAPER OUT SWITCH ADJUSTMENT ............................................................ 7-5
RIBBON TENSION ADJUSTMENT................................................................. 7-6
RIBBON DRIVE ASSEMBLY ADJUSTMENT ................................................ 7-8
viii

7.7
7.8
7.9
7.10
CHAPTERS
8.1
8.2
8.3
8.4
8.4.1
8.4.2
8.4.3
CHAPTER 9
CHAPTER 10
10.1
10.2
CHAPTER 11
11.1
11.2
11.3
CHAPTER 12
12.1
12.2
12.3
12.3.1
12.3.2
12.3.3
12.3.4
12.3.5
12.3.6
12.3.7
12.3.8
12.3.9
12.3.10
12.3.11
APPENDIX A
APPENDIX B
CONTENTS (Coot)
Page
IDLER GEAR ASSEMBLY ADJUSTMENT ................................................... 7-11
BUMPER ASSEMBLY ADJUSTMENT ..........................................................7-12
PRINT BAR ADJUSTMENT ...........................................................................7-13
LUBRICATION ................................................................................................7-15
20 rnA LAI2X-AL OPTION
GENERAL .......................................................................................................... 8-1
INSTALLATION ................................................................................................ 8-1
TEST AFTER INSTALLATION ........................................................................ 8-3
ELECTRICAL CHARACTERISTICS ............................................................... 8-3
Transmitter .................................................................................................. 8-3
Receiver .......................................................................................................8-3
Pin Assignments...........................................................................................8-3
EXPANDED BUFFER OPTION LAI2X-DL
LAI20-RE
INTRODUCTION ............................................................................................ 10-1
INSTALLATION .............................................................................................. 10-1
LAI2X-HL KEYBOARD OPTION
INTRODUCTION ............................................................................................ 11-1
INSTALLATION .............................................................................................. 11-1
OPERATOR'S INFORMATION .....................................................................11-6
LAI2X-YL
OPTION
INTRODUCTION ............................................................................................ 12-1
INSTALLATION .............................................................................................. 12-1
OPERATOR'S INFORMATION ..................................................................... 12-7
Indicator Lights.......................................................................................... 12-7
Control Keys.............................................................................................. 12-7
SET-UP Mode ............................................................................................ 12-9
Baud Rate (Speed) .................................................................................... 12-1 0
Parity and
Data Bits.................................................................................. 12-1 0
Setting Form Length................................................................................. 12-11
Printer New Line Character ......................................................................12-12
Modem ..................................................................................................... 12-13
Secondary Channel...................................................................................12-14
Status ....................................................................................................... 12-15
Store/Recall .............................................................................................12-16
LA120 OPERATOR REFERENCE CARD
FACTORY PARAMETER SETTINGS
ix

Figure
1-1
1-2
1-3
1-4
1-5
1-6
1-7
2-1
2-2
2-3
2-4
2-5
2-6
3-1
3-2
3-3
4-1
4-2
4-3
4-4
4-5
4-6
4-7
4-8
4-9
4-10
4-11
5-1
5-2
5-3
5-4
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
FIGURES
Title Page
Operator's Console .............................................................................................. 1-3
Basic System Using LA120................................................................................... 1-3
Location of Power ON/OFF Switch and Voltage Selector Switch......................... 1-7
Location of Cover Interlock Switch...................................................................... 1-8
Paper Adjust Knob .............................................................................................. 1-8
Tractor Adjust Knobs .......................................................................................... 1-9
Carriage Adjustment Lever .................................................................................. 1-9
LA120 Site Considerations................................................................................... 2-1
Unpacking/Packing............................................................................................. 2-3
Location of Nylon Cable Tie ................................................................................2-4
Location ofLA120 SET-UP Label .......................................................................2-4
Self-Test Printout.................................................................................................2-6
Location
of Answerback Jumper..........................................................................2-7
Sample Form SET-UP........................................................................................3-14
Octal Codes Generated by Keyboard..................................................................3-16
Characters Generated by Keyboard with
CTRL Key Held Down.........................3-8
LA120 Block Diagram .........................................................................................4-2
ROM Placement ..................................................................................................4-4
RAM Address Map ..............................................................................................4-5
Forward Print Start............................................................................................4-14
Reverse Print Start .............................................................................................4-15
Note A Branch Form ..........................................................................................4-23
Full Duplex........................................................................................................4-24
Supervisory Control...........................................................................................4-25
Coded Control with Reverse Channel.................................................................4-26
Coded Control Without Reverse ChanneL..........................................................4-29
Entry Organization Within a Table Element .......................................................4-29
Logic/Power Board Connectors...........................................................................5-7
DC Servo Signals ..................................................................................................5-9
Encoder
Output Waveform ................................................................................ 5-1 0
Encoder Circuit Board........................................................................................ 5-11
c/> 1 and c/>2 Clock Signals .....................................................................................5-12
8080A Addressing Output ..................................................................................5-13
DC Wake Up Waveform ....................................................................................5-13
Solenoid Signal
Output of DC305.......................................................................5-15
Drive Signal
to Print Solenoid ............................................................................5-16
Head Enable
vs Drive SignaL..............................................................................5-17
LA120 Baud Rate Clocks ...................................................................................5-18
USART I/O Signals...........................................................................................5-20
Keyboard Scan Waveform.................................................................................. 5-21
Keyboard Scan Waveform with Key Pressed ......................................................5-22
Key Circuit Waveform .......................................................................................5-23
Keyboard Scan for Chip E8 ................................................................................5-23
Line Feed Signal
Output of DC305.....................................................................5-24
Line Feed Amplifier
Input vs Output ..................................................................5-25
Line Feed Run Signal .........................................................................................5-26
Bell Amplifier
Input ...........................................................................................5-27
Bell Amplifier
Output .........................................................................................5-28
x

Figure No.
6-1
6-2
6-3
6-4
6-5
6-6
6-7
6-8
6-9
6-10
6-11
6-12
6-13
6-14
6-15
6-16
6-17
6-18
6-19
6-20
6-21
6-22
6-23
6-24
6-25
6-26
6-27
6-28
6-29
6-30
6-31
7-1
7-2
7-3
7-4
7-5
7-6
7-7
7-8
'7-9
7-10
7-11
7-12
7-13
8-1
8-2
10-1
10-2
FIGURES (Cont)
Title Page
Assembly Removal Sequence ...............................................................................6-2
Printer Housing Removal and Installation............................................................ 6-3
Print Head Removal and Installation ...................................................................6-4
Print Head Cable...................................................................................................6-6
Belt Tension Spring Location ...............................................................................
6-7
Belt Tension Spring (Detailed View) ..................................................................... 6-8
Carriage Assembly and Front Carriage Shaft Removal and Installation................ 6-9
Carriage Eccentric Bearing and Lever Removal and Installation.........................6-12
Rear Carriage Shaft and Plain Bushing Removal and Installation....................... 6-13
Ribbon Drive Pulley Removal and Installation................................................... 6-15
Ribbon Drive Assembly Removal and Installation .............................................6-16
Ribbon Drive Assembly (Detailed View) ............................................................6-17
Fafnir Bearing and Ribbon Eccentric Removal
and Installation..........................6-19
DC Motor/Encoder Assembly Removal and Installation ................................... 6-21
Tractor Drive Shaft and Tractor Assembly Removal and Installation .................6-22
Tractor Phasing Adjustment............................................................................... 6-23
Idler Gear Assembly Removal and Installation...................................................6-24
Stepping
Motor Assembly Removal and Installation ..........................................6-25
Stepping
Motor Mounted on Side Plate..............................................................6-26
Ribbon Chassis Assembly Removal
and Installation...........................................6-27
Cover Interlock'Switch
.. ~ .....................................................................................6-28
Ribbon Spool RatchetWheel
and Friction Disk Replacement ...............:............6-29
Keyboard/Numeric Pad Removal and Installation............................................. 6-31
Power Supply Assembly Removal and Installation .............................................6-32
Power Supply Assembly in Position ....................................................................6-34
PrinterMechanism Assembly Removal and Installation .....................................6-36
Cabinet Reference Holes ....................................................................................6-37
.CVT Power Supply Module Removal and Installation........................................6-38
Power Entry Bracket Assembly Removal and Installation...................................6-39
Fan Removal and Installation ............................................................................ 6-41
Logic/Power Board Removal and Installation....................................................6-42
Print Head Adjustment ........................................................................................7-2
Printer Mechanism Alignment..............................................................................
7-3
Paper Guide Adjustment......................................................................................7-4
Paper Out Switch Adjustment .............................................................................. 7-5
Ribbon Spool Tension Adjustment.......................................................................7-6
Ribbon
Threading/Drag Test............................................................................... 7-7
Ribbon Drive Adjustment....................................................................................7-9
Ribbon Drive Assembly .....................................................................................7-10
Idler
Gear Assembly........................................................................................... 7-11
Bumper Assembly Adjustment ...........................................................................7-12
Print Bar Adjustment .........................................................................................7-14
Carriage Shaft Lubrication.................................................................................7-15
Ribbon Drive Assembly Lubrication ..................................................................7-16
Installation
of 20 rnA LA12X-AL Option.............................................................8-2
20 rnA Current Loop Connector........................................................................... 8-3
LAI2X-HL Keyboard........................................................................................ 10-2
LAI2X-YL Keypad............................................................................................ 10-3
xi

Figure No.
11-1
11-2
11-3
11-4
11-5
12-1
12-2
12-3
12-4
12-5
12-6
Table
1-1
1-2
1-3
1-4
1-5
1-6
1-7
1-8
1-9
2-1
2-2
2-3
2-4
2-5
2-6
3-1.
3-2
3-3
3-4
3-5
3-6
3-7
3-8
3-9
3-10
4-1
4-2
4-3
4-4
FIGURES (Coot)
Title Page
Printer Housing Removal and Installation..........................................................11-2
Terminator Card Removal .................................................................................11-3
Keyboard Cable Installation...............................................................................11-4
Keyboard Installation .........................................................................................11-5
Label Installation ...............................................................................................11-6
Printer Housing Removal
and Installation..........................................................12-2
Terminator Card Removal .................................................................................12-3
Keyboard Cable Installation...............................................................................12-4
Keypad Installation.............................................................................................
12-5
Self-Test Printout ..................................................... ~ .........................................12-6
Form Length .................................................................................................... 12-11
TABLES
Title Page
Related Documentation ....................................................................................... 1-1
LA120 Console Indicators..................................................................................... 1-2
LA 120 Console Local Control Keys ..................................................................... 1-4
LA120 Console SET-UP Keys..............................................;............................... 1-4
LA 120 Console Control Character Keys............................................................... 1-5
LA 120 Console Miscellaneous Keys ..................................................................... 1-6
Alarm Indicators................................................................................................1-10
LA120 Internal Tests..........................................................................................
1-11
Operator Troubleshooting.................................................................................. 1-11
Summary of LA120 EIA Interface Signals ............................................................2-8
Printer Specifications.......................................................................................... 2-1 0
Keyboard Specifications.....................................................................................2-12
Communications Specifications..........................................................................2-13
Physical Specifications........................................................................................2-14
Paper Specifications ...........................................................................................2-15
LA120 Escape Sequences....................................................................................... 3-3
United States ASCII Character Set.......................................................................3-6
Code Differences Among National Character Sets................................................3-7
Escape Sequences Transmitted in Alternate Keypad
Mode ...................................3-9
LA
120 Control Characters ................................................................................. 3-1 0
APL Character Set ..... ~ .......................................................................................3-12
Escape Sequences for Sample Form ............................. ~ ......................................3-13
Synchronization Limits ......................................................................................3-15
Control Character Keys........................................................... ~ ..........................3-17
Variations in
Control Character Locations .........................................................3-17
LA120 Memory Read/Write Decoding ................................................................4-3
I/O Space Allocation ...........................................................................................4-3
Interrupt Vectors..................................................................................................4-4
Keyboard Addressing...........................................................................................4-6
xii

TABLES (Coot)
Table No. Title Page
4-5 LAI20LEDs ........................................................................................................ 4-7
4-6 Seven Segment Display Counter........................................................................... 4-8
4-7 Non-Volatile Memory Operations........................................................................4-8
4-8 8251A
USART Ports............................................................................................4-9
4-9 Utility I/O Ports.................................................................................................4-10
4-10 Disconnect Generation
vs SET-UP Commands ..................................................4-18
5-1 LA 120 Troubleshooting Procedure....................................................................... 5-2
5-2 DC Supply Voltages............................................................................................. 5-8
5-3 Line Feed Amplifier Test....................................................................................5-26
7-1 Lubrication Points.............................................................................................. 7-15
8-1 20 rnA LAI2X-AL Option Kit .............................................................................. 8-1
11-1 LAI2X-HL Installation Kit ................................................................................ ll-l
12-1 LAI2X-YL Installation Kit ................................................................................ 12-1
12- 2 Printing Self-Test................................................................................................ 12-6
12-3
Nonprinting Self-Test......................................................................................... 12-6
12-4 Entering/Exiting SET-UP Mode ........................................................................ 12-9
12-5
Baud Rate Selection.......................................................................................... 12-10
12-6 Parity/Data Bits Selection ................................................................................ 12-11
12-7 . Form Length Selection ..................................................................................... 12-12
12-8 Carriage Return/Line Feed Responses .............................................................12-12
12-9 Selection of Carriage Return/Line Feed Responses...........................................12-13
12-10 Modem Selection.............................................................................................. 12-13
12-11 Secondary Channel Selection ............................................................................12-14
12-12 Status Printout Procedure................................................................................. 12-1 5
12-13 LA120 Store Procedure.....................................................................................
12-16
12-14 LA120 Recall Procedure................................................................................... 12- 16
xiii

MA-2313A
LA120 DECwriter III
xiv

1.1 INTRODUCTION
CHAPTER 1
OPERATORS INFORMATION
The LAl20 DECwriter III terminal is basically a typewriter, with a wide range of features, that com-
municates with a computer.
The
LAl20 is easily integrated into most systems. It is compatible with both EIA and ANSI standards.
Besides the many standard features built into the basic LA
120 DECwriter III, there are a number of
options and accessories that may be added to the terminal to make it useful in an even wider range of
applications.
Operator information contained in Chapter 1 is for the general user or user already familiar with the
features
of a terminal.
It contains the following information:
• Description of operator's console
• Description of alarm indicators
• Operator Testing and troubleshooting.
Operator information is summarized on the LAl20 Operator Reference Card (Appendix A). Table 1-1
is a list of related LA 120 documents.
Tablel-l Related Documentation
Title
LAl20 User Guide
LA
120 Pocket Service Guide
LAl20 DECwriter III
Illustrated Parts Breakdown
*Available on hard copy only.
** Available on hard copy and microfiche.
For information on microfiche libraries, contact:
Digital Equipment
Corporation
Micropublishing Group
12 Crosby Drive
Bedford,
MA 01730
Hardcopy documents can be ordered from:
Digital Equipment
Corporation
444 Whitney Street
Northboro, MA 01532
Document Number
EK-LAI20-UG*
EK-LAI20-SV*
EK-LA
120-IP**
Attention: Communication Services (NR2jM 15)
Customer Services Section
1-1

1.2 OPERATOR'S CONSOLE (Figure 1-1)
The LA120 operator's console contains an office typewriter-style keyboard. The keyboard contains a
four-digit numeric display and seven indicators. There
is provision for an optional, field installable
numeric keypad.
To better understand the LA120 keyboard, think of the LA120 as two things. First, it is an input device
to a computer; that is, pressing a key sends information (a code) to a computer. Second, it is a printer;
information is sent from the computer to the printing portion
of the LA120. However, you can set up
your system to send information from the keyboard to the printer and computer
at the same time.
Figure
1-2 illustrates a basic system using an LA120.
1.2.1 Lights
The console indicator lights are listed in Table
1-2.
Indicator Light
ON tJNE
LOCAL
ALT CHAR SET
CTS
DSR
SET-UP
PAPER
OUT
NUMERIC DISPLAY
Table 1-2 LA120 Console Indicators
Meaning
The LA120
is on-line. Data is transmitted and received only while on-line.
The LA120
is in local mode. In local, LA120 operates as a typewriter and
does not transmit or receive data.
An optional alternate character set such as APL
is in use.
Transmission
of data is enabled (clear to send).
The modem
is in data mode (data set ready).
Flashes to indicate that LA120
is in SET-UP mode.
Flashes to indicate that printer
is not ready due to any of the following
conditions.
• Paper out
• Cover open
• Print head jam
The numeric display indicates the next column number during normal
operation. In SET-UP mode the numeric display may also indicate line
number, baud rate, form length, etc.
1-2

-
I
W
SHIFT
NUMERIC DISPLAY
/ ALTCHAR
c=J ON LINE LOCAL SET
o 0 0 0
TAB CLEAR TOP R BOT
SET CLEAR
ALL TOF LEFT MA RT
CTS DSR SETUP PAPER OUT
o O· 0 0
MAR STORE
CLEAR STATUS RECALL BAUD
Figure 1-1 Operator's Console
CODE TO BE
PRINTED
COMPUTER
CODE
(GENERATED
WHEN A
KEY
IS PRESSED)
MA-2306
Figure 1-2 Basic System Using LA120
456
1 2 3

1.2.2 Local Control Keys
The console local
control keys and their functions are listed in Table 1-3.
Table 1-3 LA120 Console Local Control Keys
Key Function
LINE/LOCAL Switches the LA 120 from line to local and vice versa as indicated by ON
LINE and LOCAL lights.
HERE IS Transmits answerback message. This key is not active in SET-UP mode.
LOCAL FORM FEED Performs a form feed without transmitting a code to the host computer.
LOCAL LINE FEED Advances paper one line at a time without transmitting a code to host
computer.
1.2.3
SET-UP Keys
When in SET-UP mode, most keys on the console keyboard perform a SET-UP command function.
SET-UP command functions for the top row of keys are discussed briefly in Table 1-4.
Key
SET-UP
1
"
6
@
2
#£
3
$
4
&
7
Label
SET TAB
BOT/RT MAR
CLEAR TAB
CLEAR ALL
TOF
MAR CLEAR
Tabie 1-4 LA120 Console Set-Up Keys
Function
Places LA120 in SET-UP mode where LA120 features can be
examined or changed. In SET-UP mode, the numeric display
indicates line number,
baud rate, or form length, etc.
Sets a horizontal
tab stop at the current column. When used
with SHIFT, sets a vertical tab stop at current line.
Sets right margin at current column. When used with SHIFT,
sets bottom margin at current line.
Clears horizontal
tab stop at current column. When used with
SHIFT, clears vertical tab stop at current line.
Clears all horizontal and vertical
tab stops.
Shifted
or unshifted designates current paper position as top of
form. If top of form is not the same as the top margin, paper
will move to the top margin (first printable line).
Clears left
and right margins. When used with SHIFT, clears
top and bottom margins. Left or top margin becomes J. Right
or bottom margin becomes maximum allowable in the current
characters per inch (pitch) or.form length.
1-4

Key
*
8
(
9
%
5
)
o
Table 1-4 LA120 Console Set-Up Keys (Cont)
Label
STATUS
STORE/RECALL
TOP/LEFT MAR
BAUD
Function
Prints a status message containing currently selected values
of
SET- UP features.
Recalls stored SET-UP parameters. When used with
SHIFT,
stores the current SET-UP parameters.
Sets left margin
at current column. When used with SHIFT,
sets top margin at current line.
Selects receive and transmit
baud rates. When used with
SHIFT, selects split transmit baud rates.
1.2.4 Control Character Keys
The console control character keys and their functions are listed in Table 1-5.
Key
ESC
TAB
SPACE BAR
BACK
SPACE
DELETE
RETURN
LINE FEED
CTRL
BELL
G
VT
K
FF
L
Table 1-5 LA120 Console Control Character Keys
Function
Generates code for escape (Chapter 3).
Generates code for horizontal tab.
Generates code for space.
Generates code for backspace.
Generates code for delete.
Generates code for carriage return
or the codes for a carriage return and line feed
sequence (in
auto line feed mode). In half duplex, the RETURN key can also
generate a
turnaround character in addition to its normal code or codes. The turn-
around character tells the computer that it is the computer's turn to send data.
Generates code for line feed.
When held down, modifies function or codes generated by other keys.
Hold
CTRL down and press G to generate code for the bell. G is also used in SET-
UP mode to change bell volume.
Hold
CTRL down and press K to generate code for vertical tab. K is also used in
SET-UP mode to turn keyclick on
or off.
Hold
CTRL down and press L to generate code for form feed. L is also used in
SET-UP mode to select auto line feed.
1-5