LICAL-TRC-MT Linx Technologies Inc, LICAL-TRC-MT Datasheet - Page 4

• Manufacturer Part Number: LICAL-TRC-MT
• Description: IC TRANSCODER MT BI-DIR 20-SSOP
• Manufacturer: Linx Technologies Inc
• Series: MTr
• Type: Transcoderr

Specifications of LICAL-TRC-MT

• Package / Case: 20-SSOP
• Applications: RF, IR
• Mounting Type: Surface Mount
• Supply Voltage (max): 5.5 V
• Supply Voltage (min): 2 V
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Mounting Style: SMD/SMT
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Lead free / RoHS Compliant
• Other names: LICAL-TRC-MTTR

OVERVIEW
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Many products and applications call for the transfer of button presses or switch
closures across a wireless link. Traditionally, a remote control link has operated
in only one direction, from a transmitter to a receiver. The cost associated with
transceivers has been too high to practically implement in low-cost products.
With the increasing availability of low-cost transceiver solutions, bi-directional
links are now practical and open a new world of opportunity.
In a wireless environment, maintaining the reliability and uniqueness of a
transmitted signal is generally of great importance. In a unidirectional system, IC
devices called encoders and decoders are often utilized to simplify this process.
The encoder side turns the status of a number of input lines into an encoded
serial bit-stream output intended for transmission via an RF or infrared link. Once
received, the decoder decodes, error checks, and analyzes the transmission. If
the transmission is authenticated, the decoder’s output lines are set to replicate
the status of the encoder’s input lines.
To accommodate bi-directional links, a new type of device has been developed.
Called a transcoder, this device combines a remote control encoder and decoder
into a single device, and is capable of sending commands as well as receiving
them. It is also able to receive an automatic confirmation from the remote side
indicating that its command was received and the appropriate action was taken.
For example, verifying that an automobile’s doors are all closed and have locked,
or a remote valve has actually closed.
The Linx MT Series is a revolutionary transcoder product designed for wireless
remote control applications. The same device can be used as an encoder,
decoder, or transcoder and is ideal for both uni- and bidirectional applications
and even mixtures of the two. The MT Series is easily implemented, making it
ideal for even the most basic applications, but its rich feature set also allows it to
meet the needs of far more complex applications. These features include the
ability to identify the originating transmitter, establish user permissions, select
output latch modes on a “per pin” basis, and a powerful serial interface that
allows control and information exchange with external microcontrollers or a PC.
Consider a brief example of how just one of the MT’s innovative features could
be used to transform a relatively simple application, the common garage door
opener. In competitive devices, encoded transmissions are generally either
recognized or denied based on the address. If the addresses match, the state of
all data lines will be recognized and output. The MT Series allows a user or
manufacturer to establish a user identity and profile that determines which inputs
will be acknowledged. Let’s apply this capability practically to our example: a
three door garage houses Dad’s Corvette, Mom’s Mercedes, and Son’s Yugo.
With most competitive products, any user’s keyfob could open any garage door
as long as the addresses match. In a Linx MT-based system, each individual
keyfob could easily be configured to open only certain doors (guess which one
Son gets to open!)
As you review this data guide keep in mind that it seeks to cover the full scope
of the MT’s capabilities. The implementation for a simple one button remote will
be different than a powerful targeted control, command, or status network. While
it is unlikely that all of the features of this part will be utilized at any one time, their
availability provides great design flexibility and opens up many new opportunities
for product innovation.
TRANSCODER OPERATION
TRANSCEIVER POWER CONTROL
CREATE MODE
When the transcoder first powers up, it checks the state of the ENC_SEL line. If
the line is high, then the transcoder enters Encoder mode in which it acts like an
encoder only. It pulls the TR_SEL line high to set the transceiver into transmit
mode and makes all of its status lines inputs. If the ENC_SEL line is low, then
the transcoder enters Transcoder mode and pulls the TR_SEL line low to set the
transceiver into receive mode and makes all of its status lines outputs. If the
transcoder has been previously set up, then the saved settings are applied. The
transcoder then sets the baud rate according to the state of the SEL_BAUD line
and goes to sleep until an action on one of its inputs places it into another mode.
The transcoder is able to control power to an external transceiver through the
TR_PDN line. This line can be connected to a power down or supply line of a
Linx transceiver or a similar input on another transceiver. This allows the
transcoder to power down the transceiver when it is not required, thereby
reducing current consumption and prolonging battery life.
The transcoder pulls the TR_SEL line low to place the transceiver into receive
mode and looks for valid data for 16mS or 32mS, depending on the baud rate. If
data is present on the TR_DATA line, then the transcoder enters Receive Mode.
If no data is present, then the transcoder pulls the TR_PDN line low to power
down the transceiver and goes to sleep for 150mS or 295mS. The “off” time is
approximately nine times the “on” time, resulting in a 10% duty cycle, greatly
reducing the transceiver’s current consumption. However, there may be a lag
time from when the transmitting transcoder activates to when the receiving
transcoder responds. The transcoder enters Receive Mode when it sees a valid
packet, so there would only be a lag for the first packet.
This cycle continues until data is received placing the transcoder into Receive
Mode, until a status input line is taken high placing the transcoder into Transmit
Mode, or the CRT/LRN line is taken high placing the transcoder into Serial Mode,
Learn Mode, or Create Mode.
The Create Mode allows the generation of a unique address to ensure the
security of transmission and prevent unintentional operation of devices. The MT
Series transcoder allows for the creation of 16,777,216 (2
The assignment of the status lines as inputs or outputs also occurs in this mode.
Create Mode is entered by pulling the ENC_SEL line high at the same time as
the CRT/LRN line. The address is randomized for as long as the CRT/LRN line
is high (the ENC_SEL line is not checked once the process is begun, so it can
be held high or released). Once the line is pulled low, the resulting address is
saved in memory and the transcoder will be ready to accept the status line
assignments. Each line that is to be an input should be pulled high. Any lines that
are not taken high will be set as outputs. The transcoder saves the assignments
and goes to sleep when the CRT/LRN line is taken high again or when it times
out after 15 seconds.
24
) possible addresses.
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