EDE1144/SO 查看數據表（PDF） - Unspecified
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EDE1144/SO Datasheet PDF : 7 Pages
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+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).
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