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becoming an output only when sending the data stream or responding to a
serial command. These are described more in the Serial Interface section.
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 will be 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. The figure below shows the order and
timing of the serial interface.