Texas Instruments 990 Manual page 37

~~-~~~~~~~---
~
945424-9701
i.._Xo-xa
:-
u1-40
u1-14
DATA
CONTACT
-32
.
KEYS
-.
MATRIX
u1-13
YO-Y9
__. Ut-17
.
26
u1-12
u1-11
SHIFT( 2)
_.. u3-9
S1
·~ u 1-20 u1-10
• 12 •
u1-9
CONTROL
MODE
-: u3-4, 2
u1-a
KEYS
u1-7
UCL
•
~.13-10
U4-4
S2
-: u t-29
Ul-16~
-..~4-1
us
5 _ _ ; ; ,
REPEAT-
OPTIONAL }
LOCK
SWITCH
{
/
AUDIO
TO
J4-4
~
OPTIONAL
L..
SPEAKER
AUDIO U 2-5
r--
J3-1 L
FEEDBACK
"' "
CIRCUIT
(A)136265
Figure 1-17. Model 911 VDT Keyboard
Block
Diagram
KEYSWITCH MATRIX
OT
THE Y SCAN LINES ARE IN
A PLANE PARALLEL, BUT N
IN CONTACT WITH, THE X
SCAN LINE PLANE. A TYPIC
KEYSWITCH HAS A DIODE IN
SERIES WITH IT AND THESE
TWO COMPONENTS RUN BE-
TWEEN A Y SCAN LINE AN
AL
D
AN X SCAN LINE.
(A)t 36266
XO
X1
X2
X3
X4
X5
X6
X7
X8
YO Y1 Y2 Y3 Y4
hl L I I
7
l¥7
a
l
~
KBDT1
'
7
KBDT2
_,
7
KBDT3
~
7
KBDT4
~
7
KBDT5
'
7
KBDT6
'
7
KBDT7
\.
7
KBDTB _\.
7
KBSIN- ~
7
REPEAT_\.
7
TO
u2-s
Y5 Y6
I L
Jt-1
Jt-5
J1-6
J1-a
Jt-9
Y7
TO POWER/
LOGIC PWB
YB
Y9
L·L
Figure 1-18. Model 911 VDT Keyboard Contact Matrix
1-27
Digital Systems Division