LICAL-TRC-MT001 Linx Technologies, Inc., LICAL-TRC-MT001 Datasheet - Page 8

• Manufacturer Part Number: LICAL-TRC-MT001
• Description: Mt Series Transcoder Data Guide
• Manufacturer: Linx Technologies, Inc.

SERIAL OUTPUT
Figure 8: MT Series Transcoder Open Access Serial Output
Figure 9: MT Series Transcoder Locked Access Serial Output
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SER_IO
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. 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.
start
start
SER_IO
b0
b0
b1
b1
b2
b2
00
b3
b3
ADR 1
b4
b4
00
b5
b5
TX ID
ADR 2
b6
b6
STATUS CUSTOM
b7
b7
ADR 3
stop start
stop start
STATUS CUSTOM
b0
b0
b1
b1
FF
b2
b2
b3
b3
FF
b4
b4
b5
b5
b6
b6
b7
b7
stop
stop
SERIAL MODE
Figure 10: MT Series Transcoder Serial Programming
SER_IO (INPUT/OUTPUT)
MODE_IND (OUTPUT)
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.
Time t1 in the figure above does not have to be any specific time, just so long as
the SER_IO line goes high before the CRT/LRN line. Time t2 should be greater
than 120µS (typical of 35mS, see the Mode Entry Timings section) to ensure that
the transcoder goes into Serial Mode. There is not a maximum time specified.
Once in Serial Mode, the transcoder waits for the start byte (0x00) of the serial
command.
The timings associated with each command and the transcoder’s response are
listed in Tables 7 (9,600bps) and 8 (28,800bps).
To send consecutive commands, keep the CRT/LRN line high and take the
SER_IO line high within 50µS of the MODE_IND line going low.
It should be noted that all of the settings are written into non-volatile memory, so
they will be retained if power is removed from the chip. This includes all values,
such as custom byte and target address, as well as the enabled / disabled states.
CRT/LRN (INPUT)
start
b0
b1
t
b2
1
t
2
00
b3
b4
C
b5
C
SER_IO = INPUT
Command
b6
C
b7
C
stop start
C
C
FF
b0
1mS
b1
b2
4mS
b3
00
b4
b5
A
Acknowledge/Response
b6
A
SER_IO = OUTPUT
b7
A
stop
R
R
R
R
FF
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