MCl~19
2-OF-8 KEYPAD-TO-BINARY ENCODER
The MC14419 is designed for phone dialer system applications, but
finds many applications as a keypad-to-binary encoder. The device con-
tains a 2-of-8 to binary encoder, a strobe generator, and an illegal state
detector. The encoder has four row inputs and four column inputs, and
is designed to accept inputs from 16 keyswitches arranged in a 4x 4
matrix. For an output on the four data lines, one and only one row along
with one and only one column input line must be activated. All other
combinations are suppressed by the illegal state detector to eliminate
false data output.
The strobe generator produces a strobe pulse when any of the 10
keys corresponding to numerals O through 9 are depressed. The strobe
output can be used to eliminate erroneous data entry due to contact
bounce. For a strobe output to occur, the key row and column input
lines must remain stable for 80 clock pulses after activation. When the
*,,}tt
contact bounce has settled and 80 clock pulses have occurred, the out- t’
put will be a single strobe pulse equal in width to that of the clock low..#<}~’ \>,.,$.,?,!,
state. The strobe generator will output one and only one pulse eq,ch j,<
time a numerical key is depressed. After the pulse has occurred,,$x+se ““
and bounce due to contact break will not cause another stro@#iQQ15&.
With a 16 kHz input clock frequency, the pulse occurs 5 ms a~t~~th,$last
bounce.
.++\,%‘./,\.\
)~~<!.F?,::’k:+>
‘!%.
‘i\}.
. Suppressed Output for Illegal Input Codes
,>.> >f,i$
L SUFFIX
CERAMIC PACKAGE
CASE 620
P SUFFIX
PLASTIC PACKAGE
CASE W
ORDERING INFORMATION
MC14XXX —
suffix Denotes
L = Ceramic
L P = Plastic
nPIN ASSIGNMENT
1 RI
2 R2
3 R3
4 R4
5 cl
6 C2
v~~
Clock
ST
D4
D3
02
16
15
14
13
12
11
7 C3
D1 10
8 Vss
C4 9
This device contains circuitry to protect
the inputs against damage due to high static
voltages or electric fields; howver, it is
advised that normal precautions b taken
to avoid application of anv voltage higher
than maximum rated voltages to this high
impedance circuit. For proper operation it
IS recommended
that Vin and Vout be
constrained to the range VSS < (Vin or
Vout) < VDD.
MOTOROLA INC , lW
—
DS9892
