Linx Technologies LICAL-TRC-MT - Manual (Page 9)

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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 has been
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 line outputs.
If Confirmation is enabled, the transcoder 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 gets number ‘1’, the second gets 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.
LATCH Mode
The transcoder has two output options based on the state of the LATCH
line. If the line is low, then all of the status line outputs are momentary,
meaning that they are high for as long as a valid signal is received. Once
the signal stops and the transcoder times out, the lines are pulled low.
If the LATCH line is high, then the transcoder uses a Latch Mask on the
outputs. By default, all of the status line outputs are set to latch, so the
transcoder pulls a data line high upon reception of a valid signal and
holds it high until the signal is received a second time, at which point the
transcoder pulls it low. The transcoder must see a break and time out of
Receive Mode between valid transmissions before it toggles the outputs.
The Latch Mask can be changed through the SIE so that individual status
lines can be set as latched or momentary. The Serial Mode section has
more information on the SIE.
Targeted Device Addressing
One of the powerful features of the MT is Targeted Device Addressing.
This is the ability to target the specific device that is to acknowledge the
transmission. This is accomplished by entering the address of the target
device through the SIE. For example, if a master controller needs Device
10 to activate, a microcontroller or PC can be used to program the address
of Device 10 into the transcoder in the master controller. The transcoder
then broadcasts that address with the commands, and only Device 10
responds. This enables many types of master-slave, peer-to-peer, and even
basic networking systems to be quickly realized. The simple command
set and open architecture allow such systems to be implemented in many
ways. Application Note AN-00157 goes into this feature in more detail.
Targeted Device Addressing only needs to be enabled on the transmitting
side. The receiving side identifies the packet as a targeted packet and
responds appropriately. This option is disabled by default.