Linx Technologies LICAL-TRC-MT - Manual (Page 11)

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Serial Output
Upon reception of every valid packet, the transcoder outputs a serial data
stream containing information about the transmission. The information
takes two forms depending on the User Access setting.
If the User Access is set to open, then the serial output consists of a start
byte, the three byte address of the transmitting device, a status line byte, a
custom data byte and a stop byte. The start byte is 0x00 and the stop byte
is 0xFF.
If the User Access is set to locked, then the serial output consists of a start
byte, TX ID byte, status line byte, custom data byte and a stop byte. The
start byte is 0x00 and the stop byte is 0xFF.
The status line byte reflects the states of the status lines, ‘1’ for high
and ‘0’ for low. This represents the current logic states of the outputs,
not the command that was received, so that the states of latched lines
are correctly represented. Line D0 corresponds to bit b0 in the byte, D1
corresponds to b1, and so forth. This allows applications that use an
embedded microcontroller to read the transmitted commands without
having to monitor eight hardware lines.
The TXID and Custom Data bytes are described in their own sections.
The bytes are output asynchronously least significant bit first with one
start bit, one stop bit, and no parity at the baud rate determined by the
SEL_BAUD line. During normal operation, the SER_IO line is an input,
becoming an output only when sending the data stream or responding to a
serial command. These are described more in the Serial Interface section.
start stop start stop
SER_IO 00 ADR 3 STATUS CUSTOM FF
b0 b1 b2 b3 b4 b5 b6 b6 b7 b7 b0 b1 b2 b3 b4 b5
ADR 1 ADR 2
Figure 11: MT Series Transcoder Open Access Serial Output
start stop start stop
SER_IO 00 TX ID STATUS CUSTOM FF
b0 b1 b2 b3 b4 b5 b6 b6 b7 b7 b0 b1 b2 b3 b4 b5
Figure 12: MT Series Transcoder Locked Access Serial Output
Application Note AN-00157 shows some example software to read the TX
ID and associate it with a particular transcoder.
This feature is useful in applications that need to track and record activation
attempts. The transcoder validates that the command is from an authorized
transmitter and an external microcontroller or PC can record the TX ID and
status line activation and time into a log. The Custom byte can also be
used as an additional validation or to send a sensor reading that also needs
to be logged.
Serial Mode
One of the most powerful features of the MT Series is its Serial Interface
Engine (SIE). The SIE allows the user to monitor and control the device
configuration settings through an automated system or PC rather than
manually through the hardware lines. While serial programming is not
required for basic operation, it enables the advanced features offered
by the MT, such as Targeted Device Addressing and Custom Data
transmissions.
The SIE consists of twenty commands. The transcoder outputs an
acknowledgement once it has received each command, and then a
response of up to four additional bytes if required by the command.
Serial Mode is entered by taking the CRT/LRN line high while the SER_IO
line is high. The MODE_IND line goes high for as long as the SER_IO line
is an output, allowing it to be used with RS-232 style handshaking. Each
byte is sent LSB first with one start bit, one stop bit, and no parity at the
baud rate determined by the SEL_BAUD line. After the last command byte
is received, there is a 1ms pause while the SER_IO line is changed to an
output, then a 4ms pause while the transcoder processes the command.
Then it outputs the acknowledgement and a response if appropriate. The
SER_IO line is changed to an input as soon as the MODE_IND line drops
after the acknowledgement is sent. Figure 17 shows the order and timing
of the serial interface.