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Número de pieza | EDE1144 | |
Descripción | Keypad Encoder IC | |
Fabricantes | E-Lab | |
Logotipo | ||
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EDE1144 Keypad Encoder IC
4 x 4 Matrix Keypad Encoder IC
EDE1144
RS-232 Output 1
0=2400, 1=9600 Baud 2
Connect to +5V 3
Connect to +5V 4
Digital Ground 5
Row 0 Output 6
Row 1 Output 7
Row 2 Output 8
Row 3 Output 9
XMIT
Baud
+5V
+5V
GND
R0
R1
R2
R3
Beep
Valid
OSC1
OSC2
+5V
C3
C2
C1
C0
18 Beeper Output
17 Data Valid Output
16 Oscillator Conection
15 Oscillator Connection
14 Connect to +5V
13 Column 3 Input
12 Column 2 Input
11 Column 1 Input
10 Column 0 Input
Functionality & Feature Set:
• Automatic key repeat after delay
• Contact debouncing
• Keybeep provides tactile feedback to operator
• Electrically quiet (reduced EMI) keypad scanning
• Serial / Parallel outputs available
• Data Valid output signal for interrupt activation
• 2400/ 9600 serial Baud rates
• Available in 18 pin DIP or SOIC packages
• Interfaces to any microcontroller or microprocessor
• Cost effective for OEM applications
The EDE1144 Keypad Encoder IC is designed to interface a matrix-type 4 row x 4 column (16 key
or less) keypad to a microcontroller or other host processor. A one-wire serial or four-wire
parallel interface returns the keypress data and can be used in conjunction with a 'data valid'
signal for polled or interrupt-driven applications. The EDE1144 provides enhanced keypad
features such as contact debouncing and key auto-repeat in an easy-to-use package that will lower
software overhead in the host microcontroller and reduce the I/O pin requirements from eight to
one, frequently resulting in the use of a less costly host microcontroller in your design.
In addition, the EDE1144 is electrically quiet. Many keypad encoders continually scan the
keypad, radiating EMI noise from the wires leading to the keypad (resulting in trouble during
emissions testing & final product certification & approval). The EDE1144 reduces this problem by
monitoring the keypad with unchanging signals, and then scanning only once each time a
keypress is detected.
Copyright © 1999 E-Lab Digital Engineering, Inc. All Rights Reserved.
Page 1/7
1 page +5V
EDE1144 Keypad Encoder IC
+5V
Beeper
1K Ohm
EDE1144
XMIT
Baud
+5V
+5V
GND
R0
R1
R2
R3
Beep
Valid
OSC1
OSC2
+5V
C3
C2
C1
C0
4 MHz
330 Ohm 4 x 4 Keypad
Data Valid / Interrupt Output
Serial Output
4.7K Ohm
D0 (LSB)
D1 Parallel Outputs
D2
D3 (MSB)
Figure Two: Schematic of Keypad Connection
Figure Two illustrates a typical connection of a 4x4 keypad to the EDE1144. Note that R0-R3
(Pins 6-9) are connected to the keypad rows through 330 Ohm resistors. They are present to
prevent a short circuit during the scan cycle in case more that one key is being held at a time, and
they can also help to lower radiated emissions from the keypad wires. The 4.7K Ohm resistors on
the keypad columns are pulldowns to prevent the EDE1144 column inputs from floating or
oscillating. Pulldowns should be present on all four column inputs (C0..C3) regardless of the
keypad size or configuration being used. Note: Power and Ground connections have been
omitted from the EDE1144 hookup shown in Figure Two to simplify the illustration. They must
be connected in actual operation. Also, when using a 4MHz resonator with internal capacitors,
the third (center) pin should be connected to ground.
PARALLEL DATA CONNECTION
To read data from the EDE1144 in a parallel format the host microcontroller will input from the
four data inputs D0,D1,D2, & D3, which also serve as the row drive signal pins R0,R1,R2, & R3
(see Figure Two). While the EDE1144 is waiting for a keypress, it will hold these lines at 1111
(all high). Once a key is pressed, the data output pins will toggle while the keypad is scanned so
that the EDE1144 can determine which key was pressed. Then, the appropriate data value (see
Table One) will be output onto the data outputs (via the row output pins), and the Data Valid
Output (Pin 17) will go low. This pin will stay low for 50 mS, during which the Data Output pins
will hold the keypress data. The keypress data should be sampled during this 50mS window.
Both the Parallel & Serial Data outputs are activated on each keypress (and autorepeat cycle);
designers using the parallel data outputs can ignore the serial data output (and vice versa -
designers using the serial data output can ignore the parallel data output).
Page 5/7
5 Page |
Páginas | Total 7 Páginas | |
PDF Descargar | [ Datasheet EDE1144.PDF ] |
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