Centronics 705 User manual

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MODEL 705
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PRINTER
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37400745 REV C FEBRUARY 1982
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TECHNICAL MANUAL

THE INFORMATION CONTAINED HEREIN IS
PROPRIETARY AND IS NOT TO BE RELEASED
OR REPRODUCED WITHOUT WRITTEN PER-
MISSION OF CENTRONICS data computer corp.
SERVICING INFORMATION FOR YOUR PRINTER MAY BE
OBTAINED BY CALLING THE NUMBERS LISTED BELOW.
(ASK FOR FIELD ENGINEERING)
CEnTRDntcs·
data computer corporation
Hudson, New Hampshire 03051
Tel. [phone], TWX. [phone], TLX. 94-3404
Field Engineering Headquarters -[phone]
-Regional Sales Offices -
Eastern Region (Mass.):
Central Region (Texas):
Western Region (Calif.):
Tel. [phone], TWX. 710-348-0343
Tel. [phone], TWX. 910-890-4916
Tel. [phone], TWX. 910-595-1925
-Regional Field Engineering Offices -
Eastern Region (Mass.): Tel. [phone]
Central Region (Texas): Tel. [phone]
Western Region (Calif.): Tel. [phone]
Centronics Data Computer (Canada) Ltd.
Mississauga, Ontario
Tel.[phone], TWX. 610-492-4382
Centronics Data Computer (U.K.) Ltd.
London, England
Tel. [phone], TLX. 851-877801
Centronics Data Computer (France)
50 Rue Dombasle, 75015 Paris, France
Tel. [phone], TLX. 202686
Centronics Data Computer (Germany), Gmbh
6000 Frankfurt am Main 71
Tel. [phone], TLX. 841-413224
Centronics of Puerto Rico
Dorado, Puerto Rico
© Copyright 1980 Centronics Data Computer Corp.
Tel. [phone], TLX. 385-9349
Centronics (Italia) S.P.A.
Via Santa Valeria 5, 20123 Milan, Italy
Tel. 809-514
4/80 Rev. B
All rights reserved
Patents pending in U.S.A. and other countries
Printed in U.S.A.
Specifications subject to change without notice

MODEL 705
PRINTER
37400745 REV c FEBRUARY
1982
TECHNICAL MANUAL

TABLE OF CONTENTS
SECTION 1-GENERAL INFORMATION PAGE
1.1 SCOPE .................................................................. 1-1
1.2 GENERAL DESCRIPTION .................................................... 1-1
1.3 PHYSICAL DESCRIPTION .................................................... 1-1
1.4 PRINTER OPERATION ....................................................... 1-3
1.5 RELATED PUBLICATIONS ................................................... 1-5
1.6 ACCESSORIES ............................................................ 1-5
1.7 SPECIFICATIONS .......................................................... 1-6
SECTION 2-CUSTOMER SUPPLIED COMPONENTS
2.1 INTRODUCTION ........................................................... 2-1
2.2 FORMAT CONTROLLER .............................................. : ...... 2-2
2.3 COMMUNICATIONS RAM (C-RAM) FORMAT ..................................... 2-5
2.4 CHARACTER GENERATORS .................................................. 2-8
2.5 DATA TRANSFER AND TIMING ................................................ 2-9
2.6 LOADING DATA FOR PRINTOUTS ............................................. 2-12
SECTION 3-INSTALLATION AND OPERATION
3.1 INTRODUCTION ........................................................... 3-1
3.2 INSTALLATION ........................................................... 3-1
3.3 SET-UP PROCEDURE ..................................... · .................. 3-2
3.4 CONTROLS ............................................................... 3-2
3.5 OPERATING NOTES ........................................................ 3-4
3.6 PAPER SPECIFICATIONS .................................................... 3-4
3. 7 LOADING PAPER .......................................................... 3-5
3.8 RIBBON CASSETTE ........................................................ 3-7
3.9 OPERATOR MAINTENANCE .................................................. 3-8
3.10 OPERATING CHECKS ....................................................... 3-8
SECTION 4-THEORY OF OPERATION
4.1 INTRODUCTION ........................................................... 4-1
4.2 'FUNCTIONAL BLOCK DIAGRAM DESCRIPTION ................................... 4-1
SECTION 5-. MAINTENANCE
5.1 INTRODUCTION .......... : ................................................ 5-1
5.2 CENTRONICS NAMEPLATE .................................................. 5-1
5.3 RECOMMENDED PREVENTIVE MAINTENANCE (P.M.) .............................. 5-1
5.4 TROUBLESHOOTING GUIDE .................................................. 5-2
5.5 RECOMMENDED TOOLS ..................................................... 5-3
SECTION 6-ADJUSTMENTS
6.1 INTRODUCTION ........................................................... 6-1
6.2 CHARACTER PRINTING ADJUSTMENTS ........................................ 6-1
6.3 PAPER MOTION ADJUSTMENTS .............................................. 6-3
6.4 ELECTRICAL ADJUSTMENTS ................................................. 6-3
705 TM 0745-C

SECTION 7-REMOVAL/REPLACEMENT
7.1 INTRODUCTION.;, ..........•.. , ...........•..•.•.•.....•. , .•............. 7-1
7.2 COVER ASSEMBLIES ............•......•....•..•••.....•.•.......•........• 7-1
7.3 PRINT HEAD ASSEMBLY ......•.........•..•....•..•..•..•......•••......... 7-2
7 .4 RIBBON GUIDE ASSEMBLY ................••....•...•....•....••........•... 7-3
7.5 POWER DRIVER POARD ASSEMBLY ........•......•..........•.•..•.....•...... 7-3
7.6 TIMING FENCE ASSEMBLY .....•........•..•••...•....•..................... 7-3
7.7 VIDEO AMPLIFIER ASSEMBLY ...•.•.•..••.•.....•••..•.•......... : ....••..... 7-5
7 .8 . LIGHTWEIGHT CARRIAGE ASSEMBLY ........•.•..•.•......•....•..•.........•. 7-5
7.9 STEPPER MOTOR ASSEMBLY, CARRIAGE DRIVE •...•..•..•.•......•..••••........ 7-6
7.10 STEPPER MOTOR ASSEMBLY, PAPER DRIVE •..•••.••.••...• ~ .••...•............. 7-7
7.11 PLATEN ASSEMBLY ..........•...•...•••..•....•••.•.•.•••..•.•.......•.... 7-8
7 .12 TRACTOR DRIVE ASSEMBLY •.- .•...•...•.....•.••...•.........•.............. 7-9
7.13 PIN FEED TRACTORS, LEFT/RIGHT ............................................ 7-9
7.14 PRIMARY VOLTAGE ASSEMBLY ........•••.....••..........••...•........... 7·10
7 .15 CAPACITOR/RECTIFIER BRIDGE ASSEMBLIES ....•..••..••......•..••••........ 7-11
7.16 FAN ASSEMBLY ........................•.......•..•.• : ........•..•.•..•. 7-12
7.17 LOGIC BOARD ASSEMBLY ...... : .•...••.••...••••.••..•••.•.•......•.•..... 7-12
7.18 FUSES ..............• .- ..•....•...........•..•.•.•.••.•....•...•.•.•.... 7-13
7.19 RECOMMENDED SPARE PARTS LISTING ...•..••...••.••...•..•...••••......... 7-13
APPENDIX A-ELECTRICAL DRAWINGS
APPENDIX B-INSTALLATION DRAWINGS FOR 705 CUSTOMER·
SUPPLIED CONTROL PANEL AND FORMAT CONTROLLER
705 TM 0745-C
ii

SECTION 1
INTRODUCTION
1.1 SCOPE
This manual describes the Model 705 printer
manufactured by Centronics Data Computer Cor-
poration. This manual also identifies the
components that must be pesigned, built, and in-
stalled by the customer (customer-supplied com-
ponents); theory of operation, and maintenance
information for the Centronics-supplied elec-
tronics and printer mechanism.
1.2 GENERAL DESCRIPTION
The Model 705 printer consists of a print
mechanism and print control logic with micro-
processor control. The data input cable, in-
put/output logic (Format Control), which inter-
faces the input device to the print control logic,
and the control panel are designed, built, and in-
stalled by the customer (customer-supplied com-
ponent). The character generators, which contain
dot matrix character formation data and are used
in the print control logic, are also customer sup-
plied. Stepper motors are used to control bidirec-
tional print head and paper movement. Basically,
the printer is a single print head, 7x8 dot matrix,
132 column printer with aprint speed of up to 180
characters-per-second (cps). Maximum through-
put is achieved with abidirectional print head that
seeks the shortest path to the next line of data
while printing successive lines. With bidirec-
tional paper movement capability (only possible,
with rear feed), printing of subscripts, super-
scripts, overprinters, and graphics are also made
possible. An underlining capability is provided by
a ninth pin in the print head.
1.3 PHYSICAL DESCRIPTION
The printer is completely self-contained, in-
cluding the print mechanism with micro-
processor electronics and integral power sup-
plies. Space is provided for customer-supplied
electronics (format board and control panel). The
printer stand and/or forms receiving tray (not
shown) are optional. The forms receiving tray is
standard with printer stand option.
Figure 1-1 Model 705 Printer
705 TM 07 45-C
1-1

The printer covers include several plastic covers
and one sheet metal cover. The top cover, the two
side covers, and the front cover are plastic, and
the rear cover is sheet metal. The lowerpart ofthe
front cover has an opening for a customer-
supplied control panel.
The printer consists of three major units: the
print mechanism, the electronics, and the paper
handling mechanism. (See Figure 1-2)
1.3.1 PRINT MECHANISM-The print
mechanism consists of the carriage assembly,
drive mechanism, and print head. The drive con-
tains a stepper motor which drives a continuous
belt that transports the print head and carriage
assembly back and forth along the platen.
PRINTER STAND
(OPTIONAL) .
1.3.2 ELECTRONICS-Printer control is provided
by the electronics which contains the input
power transformer, de power supply, customer-
supplied format control logic (Format Controller),
print control logic (Print Controller), and power
driver board. The Format Controller interfaces
between the Print Controller and the customer-
supplied control panel and input device. The Print
Controller contains the microprocessor, firm-
ware, control logic, and regulated powersupplies.
The Format Controller isa piggyback installed on
the Print Controller. The Power Driver Board is
located in front of the printer behind the front
cover. It provides the drive signals for the print.
head solenoids and stepper motors. A Video
Amplifier Board attached to the carriage
assembly provides timing pulses for horizontal
character registration.
10330
TRACTOR
PAPER FEED
Figure 1-2 Major Assemblies
705 TM 0745-C
1-2

1.3.3 PAPER HANDLING MECHANISM-The
paper handling mechanism is a tractor feed unit
that can accommodate up to four part fanfold
forms 4 inches (10.2 cm) to 17.3 inches (43.9 cm)
wide with a 13.2-inch (33.5 cm) maximum print
width.
The printer can have rear or bottom paper feed
and can handle up to four-part forms at a slew
rate of 15 inches per second (ips).
NOTE --------..
When bottom feed is used, bidirectional paper feed is NOT
possible. Paper can only be moved upward and maintain
proper line registration.
The number of lines printed per inch (line density)
is dependent on the customer-supplied Format
Controller and Control Panel.
1.4 PRINTER OPERATION
Figure 1-3 is a basic block diagram of the printer,
and Figure 1·4 is a pictorial diagram illustrating
the particular printer components and how they
r-----,
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CONTROL SUPPLIED
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SWITCHES
CONT:: -AND INDICATORS
I FORMAT
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relate to the format control and print control logic
boards.
The printer uses a microprocessor to control
printer operations. Under program control, the
microprocessor, located on the main logic board
(Print Controller), controls the receiving ofparallel
data in a particular format from the customer-
supplied Format Controller. The microprocessor
then acts on the data received to initiate such
functions as an internal self-test and provide the
results to the Format Controller, process print-
able data and move paper. During the printing
operation, the microprocessor initiates move-
ment of the print head, carriage and paper, and
monitors feedback from the limit switches, video
system, and paper empty switch to effect proper
execution of these motion commands. It main-
tains a record of the print head position at all
times; provides printer status information to the
Format Controller; and performs other "house-
keeping" functions.
Basically, all printer functions can be grouped in·
to one of three categories: (1) character printing,
(2) paper motion, and (3) auxiliary functions.
10331
PRINT PRINT
CONTROLLER WRITE PULSES HEAD
-"'
PRINT
SOLENOID ~
HEAD
DRIVE
CONTROL
•FORMATTED
DATA 1/0
•PRINT
COMMAND CARRIAGE CARRIAGE
HEAD MOTION_.... DRIVE
STEPPER
eCARRIAGE
MOVEMENT CONTROL MOTOR
•PAPER
MOVEMENT
•CHARACTER
LINE FEED
GENERATOR
PAPER MOTION.
PAPER
(PAPER
(CLGTOMER
--
DRIVE
STEPPER
SUPPLIED)
CONTROL MOTOR)
L __ _ _
_J
2~
VIDEO 1. 2
l l
READY TO END OF
PAPER
VIDEO
SYSTEM &
PRINT PRINT EMPTY
TIMING
SWITCH SWITCH
SWITCH
FENCE
Figure 1-3 Basic Printer Block Diagram
705 TM 07 45-C
1-3

SUPPLIED BY CUSTOMER
I
I
I
I
I
I
I
CONTftOL PANEL
I
I
I
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FORMAT PRINT
SUPPLIED BY CENTRONICS
CORCUOT BREAK<R.@
mTER~---~'-RANS-•O-RME<>iR '-,
&
~.,..~~
~C DIODE BRIDGES •
CONTROLLER t-A-DD_,R•,.....ss ._us-ti I CONTROLLER ~l~es
CONTROL
""~
LEFT MARGIN INDICATOR ~ ~
RIGHT MARGIN INDICATOR~ EOP
POWER
DRIVERS
• PRINT HEAD lo
~~--<!~ CARRIAGEASSEMBt.Y
---· ~
;=,,-~~'
" MOTOR
Figure 1-4 Printer Pictorial Diagram
1.4.1 CHARACTER PRINTING-In the printer,
characters are printed by selectively activating
eight print wires aligned in a vertical column in
the print head. A ninth wire, under direct micro-
processor control, provides the underlining
capability. As the head moves across the paper,
the appropriate print wires are momentarily ac-
tivated, driving them against the ribbon, paper,
and platen to form the specified dot pattern. The
characters are printed at 10 characters per inch.
The print commands to the print wires are
developed by customer-supplied read-only
memories (PROMs or ROMs). To extract print in-
formation, the microprocessor addresses a
PROM memory location for each column within a
character.
705 TM 07 45-C
1-4
As shown in Figure 1-5, the print head is attached
to the carriage assembly, which in turn is at-
tached to a rotating carriage drive belt. The car-
riage is driven in the forward direction or in the
reverse direction by the carriage stepper motor
which rotates the belt clockwise (forward direc-
tion) or counterclockwise (reverse direction).
1.4.2 PAPER MOTION-Paper can be moved
manually by pushing in and rotating the platen
knob, or electromechanically when paper move-
ment information is received from the customer-
supplied Format Controller. The information pro-
vided by the Format Controller establishes the
direction and amount of paper movement, which
can be from .00833 inch to 34.133 inches in
.00833-inch increments per paper .movement
operation.

20147
ELECTRONIC VFU
PAPER DRIVE
STEPPER MOTOR
NOTE' DIRECTION SHOWN FOR
UPWARD PAPER MOVEMENT.
Figure 1-5 Character Printing/Paper Motion
Torque from the paper stepper motoris applied to
the tractor unit drive gears. Paper is moved up as
shown in Figure 1-5, or down by activating the
paper stepper, which turns the drive gears to
move paper until the prescribed amount of paper
movement, contained in the paper movement in-
formation acted on by the microprocessor, has
been accomplished.
1.4.3 SPECIAL FUNCTIONS-As a standard
feature, the printer can detect if it is out of paper
orthe print head jams. These conditions are con-
veyed to the customer-supplied Format Con-
trollervia printer status information from the Print
Controller.
1.5 RELATED PUBLICATIONS
The following publication provides additional
documentation of the Model 705.
1.5.1 UNPACKING/REPACKING INSTRUCTIONS
(P /N 37 407827-9001 )-The unpacking/repack-
ing instructions are attached to the outside of the
705TM0745-C 1-5
shipping container and provide the necessary in-
formation to unpack and/or repack the printer.
1.6 ACCESSORIES
The following printer accessories are available.
RIBBON CASSETTE (37740008-2001 )-Throw-
away longlife ribbon cassettes containing 70
yards of ribbon are available to the user.
UNIVERSAL PRINTER STAND (81100000-6070)-
The printer stand provides a rigid pedestal for
mounting the printerand allows for bottom orrear
paper loading.
FORMS RECEIVING TRAY, TABLE TOP OPERA·
TION (65008166-6002)-The forms receiving
tray collects and neatly stacks the forms exiting
from the rear of the printer.
TOOL KIT (63002399-6001 )-A tool kit contain-
ing all the necessary tools (screwdrivers, nut
drivers, pliers, etc.) to maintain the printer is
available to the user.

1. 7 SPECIFICATIONS
PRINT CONTROLLER INPUT /OUTPUT
Addressing Lines ............... 8-bit parallel input, TTL levels, communication RAM (C-RAM)
addressing (00
18
to 931J·
Bidirectional Data Lines .......... 8-bit parallel input/output,TTL levels, inputdata isaccording to
the following C-RAM addressing format.
Address Data
051e-081s and OA1a-OD1s
0918
101a·931s
Paper Motion Arguments
Print Command
Printable Data
001
8 Print Status
01
18
-04
18
PaperMotion Status
OE
18
PrinterSelf-Test Status
Hold It Line .................... Handshake line, TTL level, input establishing that Format Con-
troller has read/write control of C-RAM when Got It Line is low.
Got It Line ..................... Handshake line, TTL level, output establishing that Print Con-
troller has read/write control of C-RAM.
Select Line .................... TTL level, input that selects C-RAM to enable transfer of in-
coming data to occur when Got It is low.
Read/Write Control Line .......... TTL level, input that establishes direction of data transfer on
bidirectional data lines when Got It is low.
PRINTING
Printing Method ................ Impact, character by character, bidirectional
Dot Matrix ..................... 7x8 dot matrix
Print Width (Maximum) ........... 13.2"
Print Density ................... 10 cpi
Number of Copies ............... Up to four carbon copies
Print Speed .................... 180 cps
PAPER HANDLING
Paper Entry .................... Rear or Bottom Feed
Paper Movement ................ Bidirectional with rear feed
Paper Feed .................... Rear or Bottom Tractor Feed
4.0 inches (102 mm) to 17.3 inches (439 mm) paper width
13.2 inches (335 mm) maximum print width
CONTROLS
Switch ........................ Power
Manual Controls ................ Forms Thickness, Paper Advance, Paper Tensioner
PHYSICAL-ENVIRONMENTAL-ELECTRICAL
Height ........................ 8.0 inches (203 mm)
Depth ......................... 19.5 inches (495 mm)
Width ......................... 24.5 inches (622 mm)
Weight ........................ 60 lbs (27 kg) (Printer Only)
705 TM 07 45-C
1-6

Temperature ................... Operating: 40°to100°F {4° to 37°C)
Storage: -35° to 130°F (-37° to 54°C)
Altitude ....................... Operating: -1000 feet to 10,000 feet (-305m to 3048m)
Storage: -1000 feet to 10,000 feet ( -305m to 3048m)
Maximum storage time above 10,000 feet (3048m)=8
hours
Humidity ...................... Operating: 20% to 90% (No condensation)
Storage: 5% to 95% (No condensation)
InputVoltage/Frequency ......... 115 VAC +10%, -15%; 60 Hz ±1 Hz
230 VAC +10%, -15%; 50 Hz ±1 Hz
705TM0745-C
1-7

SECTION 2
CUSTOMER-SUPPLIED COMPONENTS
2.1 INTRODUCTION
This section identifies the components that the
customer designs, builds, and installs (customer-
supplied components) to complete the 705
printer, and provides information to assist the
customer in the design of the customer-supplied
components.
To make the Model 705 complete and fully opera-
tional, the following customer-supplied com-
ponents are needed:
• Format Controller-A piggyback logic board
that contains the input/output logicto interface
between the print control logic supplied with
the printer and an external (host) system and
customer-supplied control panel.
• Power Cable-A cable assembly that supplies
the Format Controller and the Control Panel
with operating voltages originating on the Print
Controller.
• Data Interface Cable-A cable assembly that
connects address, data and control lines be-
tween the Format Controller and Print Con-
troller.
Figure 2-1
705 TM 07 45-C
2-1
• Data Input Cable-A cable assembly that con-
nects input/output lines between Format Con-
troller and the host system. As shown in Figure
2-1, a cut-out is provided in the printer to
facilitate cable routing.
• Control Panel-A printed circuit board and
switch assembly that interfaces with the For-
mat Controllerto provide an operator with local
control.
• Control Panel Cable-A cable assembly that
connects the control panel to the Format Con-
troller. Figure 2-1 shows a suggested cable
routing through an existing cut-out in the
printer.
• Character Generators-Two character
generators defined as 1Kx8 devices (2708
PROM or ROM equivalent), which contain the
dot matrix information for 128 characters. The
devices are programmed by the customer and
installed on the Print Controller.
10332

2.2 FORMAT CONTROLLER
The customer-supplied FormatControlleris apig-
gyback board that mounts on five standoffs
located on top of the Centronics-supplied Print
Controller. A 6-pin connector J004, located on the
Print Controller, is provided to supply power to
the Format Controller via a customer-supplied
Power Cable. This power source is also used to
power the customer-suppled Control Panel. A
26-pin connector J002, located on the Print Con-
troller, connects address, data and control lines
to the Format Controller via a customer-supplied
Data Interface Cable.
The Format Controller serves as an interface be-
tween the Print Controllerand customer-supplied
Control Panel and host device. Communications
between the controllers is by means of a shared
256 x 8 Communications Random Access
Memory (C-RAM) located on the Print Controller.
The C-RAM is addressed and data is written into
memory according to an established format. On
signal from the Format Controller, control of the
C-RAM is taken over by the Print Controller,
which reads the data stored in the C-RAM and
operates on it. Control of the C-RAM is then
returned to the Format Controller.
2.2.1 POWER CABLE-The customer-supplied
Power Cable must be terminated at one end with
a6-pin connectorcompatible with the powercon-
nector J004, Molex receptacle, part number 1261·
(03-09-1063) (Centronics P/N 31340006-1002),
located on the Print Controller. See Figure 2-2 for
location of connector J004. Pin-out identification
and functional description is given in Table 2-1
below.
2.2.2 DATA INTERFACE CABLE-The customer-
supplied Data Interface Cable should be con-
structed using 26-wire ribbon cable with a max-
imum cable length of 6 inches (15.3 cm) and ter-
minated at one end with a 26-pin connector com-
patible with the 26-pin Data Interface connector
J002, T&B/Ansley part number 609-2629M (Cen-
tronics PIN 31240052-1002), located on the Print
Controller. See Figure 2-2 for location of connec-
tor J002. Refer to Table 2-2 for pin identification
and functional description.
Table 2-1 Power Connector J004, Pin Identification
PIN NUMBER
DESCRIPTION
1 +5
voe return
2 +12
voe ±10% at 500 mA
±2% ripple
3 ±12
voe return
4 +5 VOC ±5% at 4A ±2% ripple
5 Reserved
6
-12 voe ±10% at 500 mA
705TM0745-C
2-2

PIN NO.
1
14
2
15
3
16
4
17
5
18
26
13
25
12
24
11
23
10
9
22
PART OF PRINT CONTROLLER
\
J002 \
DATA INTERFACE I
CONNECTOR I \\
I 13 1 ,
bjg gtt=J
26 14
00797
J004
POWER
CONNECTOR
®CD
00
@@
Figure 2-2 Data Interface and Power Connector Location
Table 2-2 Data Interface Connector J002, Pin Identification
SIGNAL SOURCE
DESCRIPTION
Address 0 Format Controller Tri-state address lines that select
Address 1 + C-RAM memory location according
Address 2
to a particular format during transfer
Address 3
of data via data lines Data 0-Data 7
Address 4 from Format Controller
to Print Con-
Address 5 troller and vice-versa Least significant
Address 6 + bit is Address 0.
Address 7 Format Controller
ov Both Controllers
ov
Both Controllers
DataO Format or Print Bi-directional data lines that carry
Data 1 Controller control or printable data from Format
Data 2 I Controller
to Print Controller or status
Data3
data from Print Controller to Format
Data4
Controller. All data is transferred
Data 5 in a particular format via
C-RAM on
Data 6 the Print Controller. These lines
are
Data 7 Format or Print tri-stated when GOT
IT is high. Least
Controller significant bit is Data
0.
ov
ov
705 TM 07 45-C 2-3

Table 2·2 Data Interface Connector J002, Pin Identification (Cont.)
PIN NO.
SIGNAL
SOURCE
DESCRIPTION
8 Select Format Controller When Format Controller has access
to
C-RAM, this line, when high, selects
the CRAM to enable data transfer to
occur in direction established by
Read/Write line. Format Controller
has access to CRAM when control
line HOLD IT is high and GOT IT is
low.
21 Read/Write Format Controller When SELECT and HOLD
IT are high
and GOT IT is low, this line, when it is
high, enables Format Controller to
read data from the CRAMs via the
Data 0-Data 7 lines. When this line is
low, data from the Format Controller is
written into C-RAM.
6 Hold
It Format Controller A handshake signal. When this line is
high and GOT IT is low, Format Con-
troller has read/write control of C-RAM.
Print Controller is prohibited from ac-
cessing CRAM.
NOTE: "HOLD IT" will only be recog-
nized by Print Controller when
"GOT IT" is low.
When low, Format Controller has relin-
quished control of C-RAM and re-
quests Print Controller to act on data
in C-RAM.
19 Got It
Print Controller A handshake signal. When this line is
high, Print Controller has read/write
control of CRAM and data is being
acted on. Format Controller is pro-
hibited from accessing C-RAM.
When low, Print Controller relin-
quished control of C-RAM to Format
Controller because action caused by
data has been completed.
7 Reserved
20 Reserved
NOTE: The following signal parameters apply to the Print Controllerand must be met by the Format Con-
troll er.
1. All signal levels are TTL compatible.
2. Driving and loading requirements are equal to one (1) standard TTL load.
705 TM 07 45-C
2-4

2.3 COMMUNICATIONS RAM (C·RAM)
FORMAT
Printeraction is dictated by the Format Controller
placing parameters in the C-RAM, then lowering
the HOLD IT line while GOT ITline is lowto signal
the Print Controller that action is requested. The
parameters are written into C-RAM according to
an address format which is basically divided into
two sections. The first section is the Control
Block and occupies memory locations 00
18
to
OF1e· The second section is the Data Block and
occupies locations 10
16
to 93
16
.
The Control Block is dedicated to transferring a
print command and paper motion arguments
from the Format Controller to the Print Controller
and transferring status information on printer ac-
tion, paper motion and self test from the Print
Controller to the Format Controller.
The Data Block is dedicated to transferring infor-
mation on printable data from Format Controller
.to Print Controller. A memory map of the C-RAM
is shown in Figure 2-3.
CONTROL
BLOCK
DATA (
BLOCK
00
01
02
03
04
05
06
07
08
09
OA
OB
oc
OD
OE
OF
10 TO 93
94 TO FF
DESIGNATION
PRINTER STATUS
ACCUMULATED PAPER
MOTION STEPS, STATUS
REMAINING PAPER
MOTION STEPS, STATUS
EVENT 1, REVERSE PAPER
MOTION STEPS BEFORE PRINT
EVENT 2, FORWARD PAPER
MOTION STEPS BEFORE PRINT
EVENT 3, PRINT COMMAND
EVENT 4, REVERSE PAPER
MOTION STEPS AFTER PRINT
EVENT 5, FORWARD PAPER
MOTION STEPS· AFTER PRINT
SELF TEST STATUS
RESERVED
CHARACTER DAT A/
PRINT BUFFER
RESERVED
00935
DATA SOURCE
PRINT CONTROLLER
PRINT CONTROLLER
PRINT CONTROLLER
FORMAT CONTROLLER
FORMAT CONTROLLER
FORMAT CONTROLLER
FORMAT CONTROLLER
FORMAT CONTROLLER
PRINT CONTROLLER
FORMAT CONTROLLER
Figure 2-3 C-RAM Memory Map
2.3.1 STATUS BYTES-As shown in Figure 2-3,
memory locations 00
16
-04
16
are for status bytes
and locations 05
16
-0D
16
for arguments. Arguments
for five events are defined as four for paper mo-
tion and o.ne for print action. The five events are
performed in sequence. However, if the self-test
705 TM 07 45-C 2-5
function is requested in the Print Command byte,
only the self·test function is performed and no
printing or paper movement takes place.
Status is updated by the Print Controller before
each transfer of C-RAM control to the Format
Controller. The print function arguments are not
changed by the Print Controller, only acted on.
After completion of a "Print Command" the print
buffer (C-RAM locations 10
16
-93
16
) are returned in
a reset mode (i.e., full of space codes 20
1
J,
however, the Print Command byte is not changed.
If no print action is requested (Bit 4 of Print Com-
mand byte equals 0), the print buffer is neither in-
terrogated nor changed.
2.3.2 PAPER MOTION ARGUMENT DESCRIP-
TION-The four paper motion arguments (bytes
0516 through 0816 and OA
16
through OD
16
) are writ-
ten into C-RAM as 2-byte numbers by the Format
Controller. The Format Controller changes each
paper motion argument as needed to move paper
before and/or after each print operation. The Print
Controller reads and acts on each argument, but
does not change it. Up to 4,095 steps (34.133
inches of paper movement) can be loaded into
each argument.
As shown in Table 2-3, the argument forms a
12-bit binary number. Bits Othrough 7of the lower
order address bytes (e.g., byte 05
16
of Event 1)
contain the eight (8) least significant bits of the
argument values. Bit Othrough 3 of the higher
order address bytes (e.g., byte 06
16
of Event 1)
contain the four (4) most significant bits of the
argument values. Bits 4 through 7 of the highest
order address bytes are ignored.
Table 2-3 Paper Movement Argument
7161514
3 2 1 0
LS BYTE
7 to 4 3 2 1 0
MS BYTE
DO NOT CARE
2 BYTES FORM 12-BIT BINARY
NUMBER, WHICH REPRESENTS
THE NUMBER OF STEPS. EACH
STEP=.00833 INCH OF PAPER
MOVEMENT.
120 STEPS= 1-IN. PAPER MOVEMENT
20 STEPS= 1/6-IN. PAPER MOVEMENT
15 STEPS= 1/8-IN. PAPER MOVEMENT

2.3.3 PRINTER STATUS BYTE (ADDRESS 00
18,
Bit 0= LSB)-This byte provides the Format Con-
troller with printer status information as de-
scribed on the following page. The Print Con-
troller writes this byte into C-RAM after each
printer action before the return of C·RAM control
to the Format Controller. The transfer of control
from Format Controllerto Print Controller with all
events zero will only cause the Print Controllerto
update the status byte.
Table 2-4 Printer Status Byte
BIT NO. DESIGNATION
7 EVENT ABORTED
6 ABORT ON EVENT 1
5 ABORT
ON EVENT 2
4 ABORT
ON EVENT 3
3 ABORT
ON EVENT 4
2
ABORT, ON EVENT 5
1 FAULT/TEST FAIL
0
PAPER OUT
(Bit Ois least significant bit.)
The function of each bit set (high) in the Printer
Status byte is as follows:
Bit 7-lndicates that one of the five events was
aborted because of eitherafault orpaper-out con-
dition.
Bits 2 through 6-When bit 7 is set, indicating an
event was aborted, one of the bits 2 through 6 is
set to indicate the event in progress when the
abort occurred.
NOTE------
Events 1 through 5 are polled in sequence starting with
event 1. Any event following the aborted event is not acted
on.
Bit 0-lndicates a paper-out condition. This bit is
set anytime the printer is out of paper including
initialization or during a prime or self-test opera-
tion requested via the Print Command byte.
705 TM 07 45-C
Bit 1- Two conditions can set this bit:
1. Print head stops moving ~ams). If this occurs
during prime or initialization, no other bits are
set in this byte. If the head jams during a print
cycle, bits 4 and 7 are also set to indicate a
truncated print cycle.
2. Recognition ofaself-test failure. When this oc-
curs, Self-Test Status byte should be polled to
determine cause of failure.
2.3.4 SELF-TEST STATUS BYTE (ADDRESS
OE
18
)-This byte provides the results of a self.
test operation, which is initiated by the Format
Controller when it sets bit O in the Print Com·
mand byte. The Print Controller performs the self·
test, then writes the results in the self-test byte
location OE
16 according toTable
2-5. When abit is
set (high), it indicates a failure in the test being
performed. A failure due to a paper-out condition
is flagged in the Printer Status byte.
2-6
Table 2-5 Self-Test Status Byte
BIT NO.
DESIGNATION
CHIP
7 Head Jam/No Head N/A
Movement
6
Bad Video Count N/A
5
Bad Character ROM #2
ME33
4
Bad Character ROM #1
ME34
3 Scratch
Pad RAM 8156
ME7
Check
2
C-RAM #2 Check
ME32
1
C-RAM #1 Check
ME31
0
CRC on 8755A
MES
The function of each bit set(high) in the Self-Test
Status byte is as follows:
Bit 7-lndicates incorrect print head movement
caused by a problem in the head drive circuitry or
a head jam.
Bit 6-lndicates problem caused by no video or
poor video signals.

Bit 5-lndicates an illegal character set (i.e., suc-
cessive pin firing or character set PROM/ROM #2
is not functioning correctly).
Bit 4-lndicates an illegal character set (i.e., suc-
cessive pin firing or character set PROM/ROM #1
is not functioning correctly).
Bit 3-lndicates that 8156 is not functioning cor-
rectly when reading and writing the scratch pad
RAM.
Bit 2-lndicates problem when reading and
writing C-RAM #2 (i.e., the four high order bits are
functioning incorrectly).
Bit 1-lndicates problem when reading and
writing C-RAM #1 (i.e., the four low order bits are
functioning incorrectly).
Bit 0-lndicates failure during cyclical redundan-
cy check (CRC) on 8755A firmware program chip.
2.3.5 ACCUMULATED PAPER MOTION STEPS
(ADDRESS 01
16
AND 02
16
)-This two byte, 16-bit
number, is a two's complement count of steps
that paper has moved. This number is zeroed on
initialization with forward paper motion steps ad-
ded (in two's compliment, subtracted) to the
number and reverse steps subtracted. The For-
mat Controller can zero this number at each
logical top of form to obtain the number of steps
accumulated per form. Each step of motion is
equal to .00833 inches (120 steps/inch).
2.3.6 UNCOMPLETED PAPER MOTION STEPS
AFTER ABORT (ADDRESS 03
16
AND 04
16
)-lf the
Print Controller is forced to abort a paper motion
event, the number of paper motion steps that
were not completed during that event are stored
in this 16-bit number by the Print Controller.
2.3. 7 REVERSE PAPER MOTION BEFORE PRINT
(ADDRESS 05
16
AND 06
16
)-Event No. 1, 12-bit
number written by the Format Controller to re-
quest a number of paper motion steps in the
reverse direction before print.
2.3.8 FORWARD PAPER MOTION BEFORE PRINT
(ADDRESS 07
16
AND 08
16
)-Event No. 2, 12-bit
binary numberwritten by the Format Controllerto
request a number of paper motion steps in the
forward direction before print.
705TM0745-C
2-7
2.3.9 PRINT COMMAND (ADDRESS 09
16
, BIT
0= LSB)-Event No. 3, written by the Format
Controller to request action other than paper mo-
tion as shown in Table 2-6. The Self-Test bit Ois
interrogated first. If it is set, no other bit is check-
ed. If bit Ois not set, Prime then Print Data bit is
checked. When Print Data is set, Print Underline
and Print Expanded bits are checked for special
print function. When the Override bit is set, any
event, 1through 5, will be acted on regardless of a
paper-out condition.
Table 2-6 Print Command Byte
BIT NO.
DESIGNATION
7
PRIME
6 PRINT UNDERLINE
5 PRINT EXPANDED
4 PRINT DATA
3
OVERRIDE
2 RESERVED
1 RESERVED
0
SELF-TEST
(Bit 0 is least significant bit.)
The function of each bit set (high} in the Print
Command byte is as follows:
Bit ?-Causes print head to move to left margin.
Bit 6-When set along with bit 4, causes
underline printout from first through last
character data loaded into print buffer.
Bit 5-When set along with bit 4, causes ex-
panded printout of print buffer data.
Bit 4-lndicates that data is to be printed. This bit
must be set to initiate any print action. To print
underline and expanded, bits 6, 5, and 4 must be
all set to ones. For normal print, only bit 4 is set.
Bit 3-Any event (1 through 5} requested will be
processed regardless of a paper-out condition.
Bits 2 and 1-Reserved.
Bit 0-Causes the Print Controller to initiate a
self-test. This includesa RAM checkand the mov-
ing of the print head to the right-hand margin to
verify the video count. Self-test result (pass/fail) is
recorded in Printer Status Byte, bit 1, with the