IBM 4979 Operating and installation instructions

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GA34-0026-1
File No. 51-03
IBM Series/1
4979 Display Station
Description
Se,ies/1

Second Edition (March 1977)
This
is a major revision of, and obsoletes GA34-0026-0. Significant changes in this new edition
include:
Restructuring
of certain status words
Changing the format of data flow information
Changes are periodically made to the information herein; any such changes will be reported in
subsequent revisions
or Technical Newsletters. Before using this publication in connection with
the operation of IBM systems, have your IBM representative confirm editions that are applicable
and current.
Requests for copies
of IBM publications should be made to your IBM representative or the IBM
branch office serving your locality.
A form for readers' comments is provided
at the back of this publication. If the form has been
removed, send
your comments to IBM Corporation, Systems Publications, Department 27T,
P.O. Box 1328, Boca Raton, Florida 33432. Comments become the property of IBM.
© Copyright International Business Machines Corporation 1976, 1977
ii GA34-0026
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Preface v
Prerequisite Knowledge v
Prerequisite Publications v
Related Publications v
Otapter 1. Introduction 1-1
Display Station Functional Description 1-1
Attachment Feature Functional Description 1-1
Standard Features 1-2
Cycle Steal 1-2
Electronic Lock
Out Feature 1-2
Data Protect Feature 1-2
Character Set 1-2
Basic Components 1-2
Display Screen 1-2
Keyboard 1-2
Controls
1-3
Otapter 2. Operation and Instruction 2-1
Display Operations 2-1
Unformatted and Formatted Display Images 2-1
Unformatted Mode 2-1
Formatted Mode 2-1
Data Representation 2-2
Keyboard Operations 2-2
Cursor 2-2
Keyboard 2-3
SHIFT
/LOCK Keys 2-3
Graphic Alphanumeric Keys
2-3
Local Function Keys 2-5
Interrupt Request Keys 2-9
Contents
Otapter 3. Programming Input/Output Operations 3-1
Data Transfer Operations 3-1
Direct Program Control (DPC) 3-1
Cycle Steal 3-1
Initiating a Display Operation 3-1
Operate I/O Instruction 3-1
Using the IDCB 3-2
Input/Output Commands and Display Operations 3-2
Command Execution Under DPC Mode
3-2
Command Execution in CS Mode 3-4
Using the
DCB 3-5
Status Information 3-10
Condition Codes 3-10
Condition Code 2-Exception 3-10
Condition Code 3-Device End 3-10
Condition Code 4-Attention 3-11
Interrupt Identification Word 3-11
Interrupt Information Byte 3-11
Interrupt Status Byte 3-11
Cycle Steal Status Words 3-12
Status After Power and Resets 3-13
Appendix
A. Otaracters-EBCDIC Hexadecimal Equivalents A-I
Appendix B. Start I/O Examples B-1
DCB Start I/O Examples B-1
START (Read From Buffer) Input B-1
START (Set Cursor and Device Status) Output B-1
START (Write to Buffer/Protected) Output B-1
START (Write/Erase-After to End of Line) Output B-2
START (Shift Lines/Write Protected/Erase After) Output B-2
START (Erase/Unprotected) Output B-2
Index X-I
Contents iii

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This manual contains reference material and is a source of
information about the IBM Series/1 4979 Display Station
Modell, and the 4979 Display Attachment Feature.
Chapter 1 is an introduction to the general characteristics
and features of the 4979.
Chapter 2 contains information on the functions and
operation of the display screen and its associated features.
Chapter 3 discusses the data flow between the processor
and the 4979. Specific topics are:
• I/O Commands
• I/O Operations
• Status Information
Appendix A contains EBCDIC characters and
hexadecimal equivalents.
Appendix B contains specific examples of different
Start commands.
Preface
Prerequisite Knowledge
This book assumes the reader has a background in data
processing concepts and is familiar with the hexadecimal
numbering system as used in IBM systems. It is assumed
the reader has a basic understanding of displays, keyboards,
and their relationship to a processor and an understanding
of stored program concepts.
Prerequisite Publications
IBM Series/l Model 5 4955 Processor and Processor
Features Description, GA34-0021
IBM Series/l Model 3 4953 Processor and Processor
Features Description, GA34-0022
IBM Series/l System Summary, GA34-0035
Related Publications
IBM Series/l Installation Manual-Physical Planning,
GA34-0029-1
IBM Series/l Configurator, GA34-0042
IBM Series/l Operator's Guide, GA34-0039
Preface v

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The IBM Series/l 4979 Display Station (Figure 1-1) is a
table top unit
that serves as a communication link between
the user and the system.
It provides image display 9f data
transmitted to and from the processor. The display station
enables the user
to enter, modify, or delete data on the
display, and to cause the revised display to be returned
to the processor for storage or additional processing.
Manual operations (such
as displaying and altering
data, and loading programs), are performed by keying
characters from the keyboard into the display video screen.
The screen
is used to display all actions. There are no
indicator lights to be decoded, because
all information is
displayed on the screen in clear text. A console printer,
the 4974
is available as an optional feature to record
messages
as hard copy.
This chapter
is an introduction to the basic components
and features
of the IBM 4979 Display Station.
The display station connects to the attachment card (a
prerequisite for the 4979) which
is located in one of the
following rack mounted units:
• IBM Series/1 Model 54955 Processor
•
IBM Series/1 Model 3 4953 Processor
•
IBM Series/l 4959 Input/Output Expansion Unit
4953/4955/4959
Chapter 1. Introduction
Display Station FUl)ctional Description
The IBM 4979 Display Station:
• Consists of a 12-inch video monitor attached to the
processor (through the device attachment card).
• Contains an alpha-numeric keyboard.
• Is a table mounted unit.
• Displays numeric characters, upper case alphabetic
characters, and special symbols.
• Is equipped with manual intensity adjustment.
• Is used for displaying and selecting operating modes
and operator entries.
Attachment Feature Functional Description
The attachment feature card:
• Serves as the connection between the processor and the
display station.
• Interprets and executes commands from the processor.
• Provides a path for data between the processor and the
display station.
• Transfers data in parallel by byte.
• Furnishes status information to the processor and
reports condition codes after I/O instructions and
during an interrupt.
• Provides a buffer for storing data.
4979 Display
Figure 1-1.
IBM Series/l 4979 Display Station and attachment
Introduction
1-1

Standard Features
The 4979 has the following standard features:
Cycle Steal
The display station operates in cycle steal mode. In
cycle steal mode I/O operations are overlapped with
processing operations,
so that processing can continue
while I/O operations are in progress.
Electronic Lock Out Feature
An electronic lock out feature protects against unauthorized
operator entry. This feature
is provided under program
control. See
"Interrupt Request Keys" in Chapter 2.
Data Protect Feature
The data protect feature prohibits the operator from
altering protected data. This feature
is provided under
program control.
Character Set
The display station uses a 64 character subset of EBCDIC
(Extended Binary Coded Decimal Interchange Code).
Basic Components
The display station has two basic components:
• Display screen
• Console keyboard
Video Screen
The video screen displays keyboard
input.
The keyboard is used for keying information
into the system, altering data, starting and
stopping programs, and so on.
Figure 1-2. Basic Components (screen, keyboard)
1-2 GA34-o026
Display Screen
The display screen (Figure 1-2) is a 12-inch CRT (cathode
ray tube) similar to
that of a television receiver. It
has a capacity of 1920 characters arranged in a format of
24 lines of 80 characters each. The display provides a
buffer for storing data, the capacity
of the buffer is the
same
as the character capacity of the screen.
Characters displayed consist of dots generated in a
pseudo 7 x 7
dot matrix on a raster CRT scanned screen.
All information displayed
on the screen must be
regenerated periodically for retention
of the image. The
speed at which the display
is reproduced is called the
"refresh" rate. The 4979 is designed to "refresh" the
display approximately
60 times per second, creating an easy
to read display under normal lighting conditions.
Keyboard
The display station keyboard (Figure 1-2) is similar to
that of a data entry style key layout. The alphanumeric,
punctuation, and special character keys form the main
body
of the keyboard with special control keys on each
side.
The keyboard
is arranged in four different key groups:
• Shift/Lock Keys
• Graphic Alphanumeric
• Local Function
• Interrupt Request
All keys are color coded for ease of use:
• Alphabetic and graphic keys are white keys with black
letters.
• Numeric keys are light gray keys with uppershift
numbers in white and lowershift characters in black.
• Local Function and Interrupt keys are charcoal gray
keys with white letters or symbols.
The keyboard character set is:
A through Z
o through 9
$,.+-*/%@&'#
( ) 4\
= > <
! " ?
- I : ; -,
Space
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Controls
The display station has three external off-keyboard
operator controls (located on one stem):
• ON-OFF
• Brightness
• Contrast
Adjust
contrast Adjust
brightness
On
-
Off
-
These controls, located just above the keyboard on the
front
of the unit, allow for (1) powering the unit ON/OFF
and (2) adjustment of the brightness and contrast of the
display for a comfortable viewing level.
Introduction 1-3

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Display Operations
The 4979 provides a buffer for storing data. The capacity
of this buffer is the same as the character capacity of
the display screen, i.e., 1920 characters. Display data that
is stored in the buffer is presented to the operator on the
display screen in the form
of alphanumeric characters and
symbols. The display
is refreshed continuously (regenerated)
from the buffer
to maintain a constant image on the screen.
The following sections provide information on the
functions and operations
of the display screen and its
associated features.
Unformatted and Formatted Display Images
There is a fixed relationship between each buffer storage
location and its related character position on the display
screen. Buffer address locations are referenced from 0 (the
first displayable character location in the upper left corner
of the screen) to 1919 (the last displayable character
location in the
bottom right corner of the screen).
By using these address locations under appropriate
commands, a program can load a display station buffer with
a display image
that exactly satisfies the requirement.
An application program can present a display to the
operator in one
of the following modes (See Figure 2-1):
• Unformatted mode
• Formatted mode
Unformatted Mode
In unformatted mode, the display station is left unformatted
and the display user uses the screen in a free-form manner.
Formatted Mode
In formatted mode, the display image is completely or
partially formatted by the application program. There are
two types
of data fields on a formatted display. They are:
• Unprotected data field
• Protected data field
Unprotected Data Field
All operator entries will go into unprotected fields known
as input fields. The fields are highlighted on the screen
by characters
of brighter intensity. Data can be entered,
modified, or erased by keyboard action in any unprotected
input field.
Chapter 2. Operation and Instruction
Protected Data Field
The protected data field is primarily for the use of the
program, and data cannot be entered into this field
by the
operator. Protected data fields are comprised
of contiguous
protected character positions designated by the application
program. These fields are distinguishable on the screen
by
a lower intensity.
Figure 2-1. The image on your screen might look like one
of the above
Operation
and Instruction 2-1

Data Representation
All data is transmitted from the processor to the display
station buffer in EBCDIC or the appli'cable character set
(see Figure 2-2). The 64 EBCDIC characters include the
upper case alphanumeric characters, space, special graphic
symbols. Characters transmitted from the processor
that
are "outside" the 64-character EBCDIC subset are accepted,
converted
to a NULL, and displayed on the screen as a
blank.
When a character is transferred to the buffer ...
I
11000001
I
Figure 2-2. Data representation
Keyboard Operations
the buffer character comes onto the
screen during the next regeneration
from the buffer.
The keyboard enables the user to change, edit, or create
character displays except within fields protected from
keyboard operations by the program.
As messages are being
composed or modified by keyboard operations, the changes
are inserted in the buffer and displayed on the subsequent
display fresh cycle.
When the user completes an operation and presses one
of the interrupt request keys, for example the ENTER key,
an interruption informs the program; the program may then
read the modified data fields from the display buffer.
2-2 GA34-0026
Cursor
A special symbol (that resembles an underscore), called a
cursor (Figure 2-3),
is displayed beneath a character or
character position on the display screen to indicate where
the next character entered from the keyboard will be stored
(Figure 2-4). For example, when the cursor
is displayed
under one character
in a line of characters, that character
can be changed or deleted by keyboard action unless it
is
a protected character. Also, if the cursor is displayed under
a position without a display character, a character can be
inserted in that position by keyboard action unless it
is a
protected space character. However, when the cursor appears
beneath a protected character or a protected space character
position, that position cannot be modified by keyboard
action. Attempting
to do so causes the cursor to be moved
one position to the right.
One, and only one, cursor is capable of being displayed
on the screen. When the display
is turned on, the cursor is
automatically generated and displayed in the first location
on the screen (Figure 2-3), following a command from the
application program to unlock the keyboard. A power up
of the display station causes an interrupt to the application
program. The cursor can be repositioned
by the keyboard
operator and also by the program. Following a depression
of any interrupt key, the cursor is blanked as an indication
to the operator that the keyboard
is locked. A command
from the application program
is required to unlock the
keyboard and allow the cursor to reappear. The cursor
is
flashed during Insert Mode operation (see Insert Mode).
Figure 2-3. Cursor
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Figure 2-4. The cursor looks like an underscore
Keyboard
The display station has a Data Entry-typewriter style
keyboard.
The keys on the keyboard are divided into four main
groups. Refer
to keyboard and legend in Figure 2-5.
• Shift/Lock Keys
• Graphic Alphanumeric Keys
• Local Function Keys
• Interrupt Request Keys
Legend
D (Typamatic action)
[l Graphic alphanumeric
D Local function & Shift Lock
D Interrupt request
Figure 2-5. Keyboard groups
Certain keys within the Graphic Alphanumeric and Local
Function categories have typamatic action (Figure 2-6).
This means
that they have the ability to repeat their
character or operation automatically
if held down. The
typamatic keys increase operating speed. After an initial
pause after the first key entry, the typamatic keys operate
at approximately 10 key entries per second. The typamatic
action
of individual keys is discussed in greater detail
under the individual key descriptions in the following
sections.
Legend
DTypamatic action
Figure 2-6. Typamatic keys repeat their function when held down
SHIFT/LOCK Keys
The SHIFT and LOCK keys operate the same as on a
standard typewriter keyboard (Figure 2-7). When either the
left or the right SHIFT key is pressed, the upper symbols
shown on the dual character keys are displayed when their
respective keys are pressed. If the character key has no
upper symbol (such
as some alphabetic keys), the SHIFT
key has no effect on the character displayed. The SHIFT
keys are nonlocking and must be held down.
Pressing the LOCK key (wide arrow) electronically locks
the keyboard in a shifted (upshift) condition. When the
LOCK key is used, holding the SHIFT key down is
unnecessary, and both hands are free for typing. Press
either SHIFT key when ready to return the keyboard to the
unshifted (downshift) condition. This releases the
electronic lock.
Figure 2-7. Shift/lock keys
Graphic Alphanumeric Keys
These keys (Figure 2-8) represent the 64 printable
alphanumeric, space, and graphic symbols contained within
the
EBCDIC subset table. Each key entry within this group
causes the appropriate symbol
to be displayed on the screen
in the position marked by the cursor. When the character
is displayed, the cursor is moved one position to the right.
This routine
is repeated for each key entry. The end of
the display line will wrap to the beginning of the next lower
line (see discussion
of cursor wrap under Cursor Position-
ing Keys this chapter) and the end
of the bottom display
line wraps
to the beginning of the top line.
Operation and Instruction 2-3

Keys that have two characters can display either of
them, depending on the position of the SHIFT key. The
lower character displays when the character key
is pressed
and the keyboard
is in the down shifted mode (the SHIFT
key
not pressed). To display the upper character, hold the
SHIFT key down while pressing the character key or press
and release the LOCK key before pressing the character
key.
Remember, none of the Graphic Alphanumeric keys will
cause
an interrupt to the program.
Figure 2-8. Graphic alphanumeric keys
The graphic alphanumeric keys are:
Lower shift symbol
Q
W
E
R
T
Y
U
I
o
P
A
S
D
F
G
H
J
K
L
Z
X
C
V
B
N
M
@ = at sign
% =percent sign
* = asterisk
< =less than sign
- = minus sign
= slash
= comma
= period
2-4 GA34-Q026
Upper shift symbol
+ = plus
= underscore
) =right parenthesis
¢ = cent sign
\ = reverse slash
I = logical OR
1 =numeric one
2 =numeric two
3 = numeric three
& = ampersand
blank
> =greater than sign
= colon
=semicolon
"I =logical NOT
=prime apostrophe
4 =numeric four
5 =numeric five
6 =numeric six
blank
= question mark
" = quotation mark
= equal sign
= exclamation point
( = left parenthesis
7 = numeric seven
# = number sign
=comma
$ = dollar sign
=period
- =minus sign
o =zero
8 = numeric eight
9 = numeric nine
To familiarize yourselfwith the keyboard, it may be
convenient to look at the Graphic Alphanumeric keys in
groups:
• Alphabetic Characters
• Numeric Characters
• Symbol and Punctuation Characters
• Space Bar
Alphabetic Characters
All but two of the alphabetic keys (the A and Z) are dual
character keys (Figure 2-9). The alphabetic characters on
the faces of these keys are always displayed as capitals
(uppercase characters) when the key
is pressed. When the
key
is pressed with the keyboard in upshifted mode, the
numeric or symbol (on the upper
half of the key face) is
displayed.
Figure 2-9. Alphabetic keys
Numeric Characters
With the keyboard in upshifted mode, Graphic Alpha-
numeric keys display the numeric symbol shown on their
upper half (Figure 2-10).
Figure 2-10. Numeric keys
Graphic Characters
Graphic characters are located on the upper
half of most
of the alphabetic keys, and on the lower half of two of
the numeric keys. The graphic that appears on the upper
part
of the key displays only with the keyboard in shifted
mode.
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Space Bar
A space
is considered an actual character that occupies a
position or location on the face
of the screen. When the
space bar (Figure 2-11)
is pressed in upshifted mode, a
space code
or blank is entered on the screen and will
replace whatever character
is presently in that position (a
space can never be inserted in place
of a protected character
when the keyboard
is in the upshifted mode). The space bar
can be used
to cause cursor advancement to the right,
through unprotected positions,
if the keyboard is in the
down shifted position (SHIFT key down).
If a space is
desired at a position occupied by any unprotected character
other than a NULL code, the keyboard must be upshifted.
Remember, in upshifted mode the space bar replaces all
unprotected positions with blanks (space codes). In down-
shift mode, the space bar will advance the cursor without
altering data except NULLS. The space bar has typamatic
action.
Figure 2-11. Space bar
Local Function Keys
These keys (Figure 2-12), the third of the four main groups,
cause movement
of data characters or cursor within the
attachment
but they do not cause an interrupt request. The
keys in this group are:
TAB (forward)*
TAB (backward)
New Line Cursor*
Up Cursor*
Down Cursor*
Left Cursor*
Right Cursor*
DUPL/DUPC*
Erase EOL
EOS/EOF
INS Mode
DEL Mode
Reset
*These keys are typamatic keys.
Figure 2-12. Local
function keys
Cursor Positioning Keys
---I Tab
___ Move cursor left
----l New Line - Move cursor right
t Move cursor up I- Back tab
~ Move cursor down
Figure 2-13. Use
the cursor control keys to reposition the cursor
Because the position of the cursor determines where the
next character keyed will be entered, it
is important to
know how to move the cursor to any location on the screen.
The operator will want
to be able to move the cursor
around quickly to positions where data
is to be entered or
altered. These keys are part of the Local Function keys.
They provide a means
of rapid positioning of the cursor to
any character position without affecting any
of the
information already on the screen. Cursor positioning keys
(Figure 2-13) move the cursor in a horizontal (right
or left)
or vertical (up or down) direction.
eTab (forward) GTab (Backward)
Figure 2-14. Tabulator keys
Tab (Forward). This key (Figure 2-14-A) causes the cursor
to skip to the right
to the first position of the first
unprotected field it encounters; then, in typamatic mode,
skip to all first character positions of unprotected fields
encountered line-by-line in a left-to-right, top-to-bottom
movement. The first position
of an unprotected field is
the first position encountered after a protected position.
On reaching the bottom right hand corner of the screen, it
wraps to the upper left corner
of the display screen. On
a display with no unprotected fields, the cursor
is
repositioned to character location zero.
Operation and Instruction 2-5

Tab (Backward). This key (Figure 2-14-B) causes the cursor
to skip to the leftmost position
of the first unprotected
character field encountered. The leftmost position
of an
unprotected field is the character to the immediate right
of a protected character. If no unprotected position is
encountered, the cursor wraps to the upper leftmost
position
of the display image.
CUSTOMER NAf'l JOII\! DOl •
AIlDReSS REIl ROAD, ARVADA, COLOR~ Ot,TE j.UNE 11, 19/2
ITEM Dc5CRlf'Tlm, ~~
The tab key moves the cursor to the nextinput field
A =Before tab B =After tab
The back tab key moves the cursor back to the beginning
of an
input field (upper A-to-B)
or the fIrst character position of the
preceding field (lower A-to-B).
New Line Cursor. This key moves the cursor in the
following manner:
• If the screen is unformatted, the cursor is moved to the
first position
in the next line.
• If the screen is formatted, the cursor moves to the first
unprotected position on the first new line that contains
unprotected characters.
2-6 GA34-Q026
If all character positions on the screen are protected, the
cursor wraps to the first character position on line one,
that
is, the upper left corner of the display.
The New Line Cursor key is typamatic.
Up Cursor. This key moves the cursor upward (bottom to
top) one line from its current position, but in the same
character column. On reaching the top
of the screen, it
wraps
to the same position on the bottom and continues
upward again. This key
is typamatic; it will continue cursor
movement, line-by-line, until the key
is released.
Line 1
Line 24
I----t
: 121.
456
1123456
1123456
1 12~6
I'y _ "-..../
r~
I 1 2 4 5 6
1 1 2 4 5 6
1123456
1 -
___ J
Up cursor, wrap
Line 1
Line 24
r--,
1121..
456
1123456
1123456
,
t
I
1
~
~~
/,; ~ ~
1123456
I
1123456
,121456
L ___ t
Down cursor, wrap
Down Cursor. This key moves the cursor downward (top to
bottom) one line from its current position, but in the same
character column. On reaching the
bottom of the screen, it
wraps to the top and continues downward again. This key
is
typamatic; it will continue cursor movement, line-by-line,
until the key
is released.
Left Cursor. This key moves the cursor right-to-Ieft, one
character position at a time, progressing across the screen.
On reaching the left side of the screen it wraps to the right
most position on the line above. On reaching the
top left
hand corner
of the s~reen, it wraps to the bottom right
hand position and continues moving as long
as the key is
held down. This is a typamatic key.
~ ~Character Position~ r--...
~ ~
_ ~ ~ ~ ~ ~( C ~ ~ ~ ~ :·1
: 7444J )44444 I
~---------~--------~
Cursor right, wrap
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Right Cursor. This key moves the cursor left-to-right, one
position
at a time, progressing across the screen. On
reaching the right side of the screen, it wraps to the left-
most position
on the line below. On reaching the bottom
right hand corner of the screen, it wraps to the top left hand
position and continues moving
as long as the key is held
down. This key
is typamatic.
~ ~Charactcrpositi(lTl~ /"'.
~ ~
--------- .... --------
! ;;; ;p: I I s: ~ ~ ~ ~ ~J
I~ 3 3 3 3 3 3 3 3 3
4 4 4 4 444 4 4
Cursor kft. wrap
This completes the description of the cursor positioning
keys (see Figure 2-15 for summary),
but there are still more
keys in the Local
Function group.
DUPC (Down Shift-Duplicate Character)
This duplicate character key enters the character to the
left
of the cursor into the display position, marked by the
cursor, provided
that position is not a protected position.
When the character
is entered it is unprotected and the
cursor
is moved one position to the right. Because it's a
typamatic key, this routine
is repeated as long as the DUpe
key is depressed or until a protected character is encountered.
If a protected character is encountered, it remains
unchanged
and the cursor moves over one character position
to the right. The
end of the display line wraps to the next
lower line and the end
of the bottom display line wraps to
the
top line. This function operates only with the keyboard
in the down shifted mode.
DUPL (Upper Shift-Duplicate Line)
The duplicate line key enters the character located one
line step above the current cursor line, provided the
current cursor position
is not a protected character. When
the character
is entered it is unprotected and the cursor
is moved one position to the right. Because this is a
typamatic key, this routine
is repeated as long as the DUPL
key is pressed or until a protected character is encountered.
If a protected character is encountered it remains
unchanged
and the cursor moves over one position to the
right. The end
of the display line wraps to the next lower
line and the
end of the bottom display line wraps to the
top line. This key operates only with the keyboard
in
upshifted mode.
Erase
EO L (Erase to End of Line)
Pressing this key will enter a null data character (HEX
00) at the cursor position, provided it is an unprotected
position, and at all unprotected positions to the right of
the cursor through the end of the line. This will erase all
unprotected data
(protected data is skipped) from the cursor
location
to the end of the line (EOL). The cursor will be
positioned at the first position on the
next lower line
(unless
it is on the bottom of the screen, then it will wrap
to the top leftmost position). When the cursor skips to a new
line, this key will have
to be pressed to do another Erase
EOL operation.
EOS/EOF Key
EOS (Upper Shift-Erase to End of Screen). This key will
enter a null character (Hex
00) at every unprotected
position starting with the current cursor position and
ending at the lower rightmost corner
of the screen. This
erases
all unprotected data from the current cursor location
to the end
of the screen (EOS). The cursor will then wrap
to the top leftmost position
of the screen.
EOF (Lower Shift-Erase to End of Field). This key will
enter a null data character in every
unprotected position
starting with the current cursor position and every position
to the right
of the cursor until a protected position is
encountered or the end of the screen is detected. This will
erase all
unprotected data from the current cursor location
to the end
of the unprotected field (EOF). The cursor will
then move
to the first protected character or to the top
leftmost position of the screen. If the EOF key is pressed
when the cursor
is at a protected character position, the
cursor
is advanced to the next unprotected field
encountered,
or until the end of the display screen is
encountered. In this manner, the protected characters are
"skipped over."
Operation and Instruction 2-7

INS (Insert Mode)
Pressing this key places the keyboard in an Insert Mode of
operation. All of the keys will perform normally while the
keyboard
is in this mode. This mode allows entry of a
character or characters into the middle
of a line or field
without disturbing the information already displayed there.
All of the entries will be inserted at the cursor location
provided that position does
not contain a protected
character, and
that one or more null characters exists at
the end
of the line or field. Upon inserting a character
all of the unprotected characters on that line, as well as
the cursor, will be shifted one position to the right of the
cursor. This operation
is halted if the operator tries to
insert any characters into a protected location, or if any
non-null character would be shifted
out at the end of a line
or shifted into a protected location. The cursor may be
advanced to the right with the cursor control keys, skipping
over any protected locations, allowing the Insert Mode
to
be continued. The number of characters that can be
inserted
is limited to the number of blanks remaining in
that field or line.
Insert Mode continues until a Reset or a Delete key is
pressed, or until a Power-On-Reset, System Reset, Device
Reset or Halt condition occurs. (Figure 2-15 shows an
example
of inserting data.)
Note. The Insert Mode condition is denoted by a flashing
cursor on the screen.
Use the INS MODE key to insert missing information.
2-8 GA34-o026
Key Pressed
M
A
P
L
E
Space
Figure 2-15. Inserting a word moves some displayed data to the right
o
o

o
o
o
DEL (Delete Key)
Pressing the DELETE key when the cursor
is located in an
unprotected field deletes the character occupying the
position underlined
by the cursor. All characters to the
right
of the cursor in that line or field (on the same line)
are shifted one position
to the left. Null characters are
inserted at the
end of the line (or unprotected field).
If the delete is attempted at a protected field, the
delete
is not executed and the cursor is not moved. This
key places the
4979 attachment into a non-insert mode.
RESET Key
Pressing the RESET key restores the keyboard
to normal
operation. The RESET key will not reset when the display
is sending data to or receiving data from the processor.
This key
is used to deactivate the INS MODE key.
Interrupt Request Keys
The last group of keys are the Interrupt Request keys
(Figure 2-16).
ATTEN
ENTER
PF1
PF2
PF3
PF4
PF5
PF6
PF6
PF3
(Attention)
(program Function 1 lower half)
(Program Function 2 lower halO
(Program
Function 3 lower half)
(Program Function 4 upper half used with SHIFT)
(program Function 5 upper half used with SHIFT)
(Program Function 6 upper half used with SHIFT)
Figure 2-16. Interrupt request keys
The Interrupt Request keys cause an attention interrupt
request to the processor. The attachment causes a keyboard
lockout condition, which prohibits any additional key
entry, until the interrupt
is honored by the processor. The
system must be programmed
to reset the lock-out condition
with the appropriate start command. During the period the
keyboard
is in a lock-out condition, the display cursor is
blanked out as an indication to the operator. The cursor
is also blanked out when the program commands a lock-out
via an 10 instruction. None
of the Interrupt Request keys
have typamatic action.
ATTN Key
Pressing this key normally readies the keyboard and
display, ending any stopped state, however, the operation
is defined by the application program.
ENTER Key
When the ENTER key
is pressed, keyed-in data on the
display normally enters the system and
is available to be
read
by the program, however, the operation is defined by
the application program. Before ENTER is pressed, any
keyed-in data can still be changed by the operator.
Operation and Instruction 2-9