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the line to ground while trying to power down the receiver. This mode is
appropriate for receivers that have a high internal pull-up resistance, such
as those offered by Linx. If the intended receiver does not have a pull-up,
then a 100k
Ω or larger resistor to V
CC can be added to the RX_CNTL line to
activate this mode.
TX ID
The TX_ID line will output an eight-bit binary number to identify which
learned encoder sent the transmission. The number is output at the baud
rate set by the SEL_BAUD lines and will normally correspond to the order in
which the decoder learned the encoder, so the first encoder learned will get
number ‘1’, the second will get number ‘2’, and so on. An exception arises
when the memory is full, in which case the first numbers are overwritten as
described in the Learn Mode section. Application Note AN-00156 shows
some example software to read the TX_ID and associate it with a particular
encoder. The C and Visual Basic code is well documented so that it can be
modified for a specific application.
System Example
The first step in using the decoder is to set the baud rate and determine if
the outputs should be latched or momentary. Next, the decoder will need
to learn the encoder’s Code Word. This is done by momentarily pressing
the button connected to the LEARN line. The LED connected to the
MODE_IND line will begin to flash to indicate that the decoder is ready to
learn a new Code Word. One of the buttons on the transmitter is pressed
to send a signal to the decoder. Once this is done, the LEARN button is
pressed again to exit Learn Mode.
Now, when a button is pressed on the encoder, the corresponding line on
the decoder will activate. If the LATCH line is high, the data line will remain
high until the encoder button is pressed again, telling the decoder to pull
the line low.
To clear the memory of the decoder, the LEARN button is pressed and
held for ten seconds, until the LED turns off. Once the button is released,
the LED will light for two seconds to indicate that the memory has been
cleared.