Tektronix 4014 User Manual page 8

4014 and 4014-1 Users
—— _|
p . HARD
i j COPY O
COMPUTER Display Unit NIT
"S22 keyboard = | =! |
| came
W WT
2) ©
Direct Connection
foot oo ooo oo ee ~ Y
J |
I I
t 1
e — | modem }5 *—j modem --¢ —_—> a
| | Earn y / \
— oa interface terminal PERIPHERAL
communication control DEVICES
+ [aa |OO® link &
Pedestal °
2
Fig. 1-2. Data flow diagram.
Terminal
Keyboard. The Keyboard provides the operator with a
readily understandable means of inputting data to the
Computer. It is an electromechanical device which, as a
result of the operator's depressing any one of its keys,
produces electronic data that is distinctive for that key.
The electronic representation of the depressed key
provides the Terminal Control and the Computer circuits
with a form of data they can understand. This representa-
tion conforms to the American Standard Code for Infor-
mation Interchange (ASCIl).
Display Unit. The Display Unit presents data visually for
both alphanumeric and graphic operation by accepting
writing beam position and writing beam on or off signals
from the Terminal Control circuitry. These signals com-
bine in the Display Unit to give a visual representation on
the display screen of the data interchange between the
Operator and the computer.
The Display Unit contains a storage-type crt (cathode-
ray tube). The data being displayed has only to be written
once. The characteristics of the storage tube allow the
image of the data to be displayed for 15 minutes without
1-2
damage to the display screen without having to continual-
ly redraw it, as would be necessary if a television-type crt
were used. This 15 minutes can be increased to one hour
in Alpha Mode because of an automatic reduced-
intensity feature.
Terminal Control and Character Generator. This cir-
cuitry accepts data from either the Interface, the Keyboard
or from Peripheral Devices. This circuitry also provides
synchronization so that the data is handled in the proper
sequence. When data is accepted by the Terminal Control
circuits, they route this data to the Computer and/or the
Terminal Display Unit, depending upon the data source
and the function requested by the data. The Terminal
Control circuits interpret this data as a writing character,
as coordinate points on an X-Y axis (for beam position- .
ing), aS a special function to be performed (backspace,
ring bell, etc.), or as mode control information. Another
function of the Terminal Control is to allow the Terminal
status and the X and Y coordinates of any point on the
display area of the screen to be sent from the Terminal to
the Computer upon command. The Character Generator
provides character writing information to the Display Unit.
®