Sanyo ACI-A Training Manual page 6

2-1 A-D Key Identification Circuit
The key identification circuit used in this chassis uses a switched resistive ladder network in
a A-D conversion circuit to generate and send a voltage to the CPU when a key is pressed.
The CPU uses this voltage to determine which key was pressed. This resistive circuit elimi-
nates the need for encoder/decoder devices, simplifying design and adding to the reliability
of the TV.
The table shows the voltages input to CPU pin 14 and 15, when a given key is pressed.
CPU
15
14 L
3-
K1 5" ~
+—
~:j
27k K2
&
27k
10k
&3
!W
10k
5.6k
& KJ
5.6k
3.9k
~
K~
3.9k
2.2k
~ K~3
2.2k
2.7k K7
K~4
2.7k
0.27k
0.27k
lrwut
voltaqe to pin 15
—
7+
Intro It
vnltarie to
nin 14
.----- --..-=- .- . ... . .
1
Ke
K1
K2
K3
K4
K5
K6
K7
OFF
Range of voltage
0.5V-1.1 V
l.l V- 1.7V
1.7V - 2.3V
2.3V - 3.OV
3.OU - 3.6V
3.6V - 4.2V
more than 4.2V
Less than 0.5V
Function
Position Up
Postion Up
Position Down
Level Up
Level Down
Undefined
Undefined
No Key pressed
-t
Ke
K8
K9
KI O
K11
K12
K13
K14
OFF
* Range of voltage
0.5V-1.1 V
I.lv- 1.7V
1.7V - 2.3V
2.3V - 3.OV
3.OV - 3.6V
3.6V - 4.2V
more than 4.2V
Less than 0.5V
Function
-rvlAv
TVIAV
SIF System
Colour System
Undefined
Preset
Function
No Key pressed
4
.
" When the supply voltage is 5.OV.
-6-
Training Manual AC 1 Chassis