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16
Receive Mode
When a rising edge is seen on the TR_DATA line, the transcoder enters
Receive Mode. It then looks for a valid packet, meaning that there are no
errors and that the received address matches one that is saved in memory.
In addition, if Targeted Device Addressing is enabled, then the received
targeted address must match the transcoder’s local address. If no valid
data is received within 16 or 32mS (dependent on the selected baud rate)
then Receive Mode is exited. If there is a match, then the transcoder pulls
the MODE_IND line high as an indication that a valid signal was received. It
compares the received commands to the Control Permissions associated
with the transcoder that sent the signal, and reproduces the states of the
authorized status lines on the originating transcoder on its own status lines.
If Confirmation is enabled, the transcoder then pulls the TR_SEL line high
to place the transceiver into transmit mode and sends a confirmation to the
originating transcoder. It also outputs the ID of the originating transcoder, a
Command Byte that represents the states of the status lines, and a custom
data byte programmed by the user. It then looks for the next valid data
packet. If, at any time, an error or an unknown address is detected,
then the transcoder ignores the packet and looks for the next one. If the
131mS timer runs out before any valid packets are received, then the
transcoder goes back to sleep.
TX ID
The transcoder outputs an eight-bit binary number on the SER_IO line
to identify which learned transcoder sent the transmission. The number
normally corresponds to the order in which the transcoder was learned, so
the first transcoder 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.
An exception also arises if the serial interface is used to write an address
to a specific location in memory. The TX ID is output with the Status and
Custom Data bytes after every valid packet that is received, as described in
the Serial Output section.