
–
34
Typical Applications
The MT Series transcoder is ideal for replicating button presses for remote
control applications. An example application circuit is shown below.
SPDT switches are used to select the baud rate and set the latch mode.
These can be tied directly to supply or ground if they will not change.
The TR_PDN line can be connected to the PDN line of a transceiver or it
can be left floating.
SER_IO can be connected to a microprocessor or a PC to program the
transcoder through the serial command set or to record the transmitter
identity. Application Note AN-00157 has sample code.
A LED indicator is attached to the MODE_IND line to provide visual
feedback to the user that an operation is taking place. This line will
source a maximum of 25mA, so the limiting resistor may not be needed,
depending on the LED chosen and the brightness desired.
The CONFIRM line is connected to a LED to indicate that the remote
device successfully received the command.
The CRT/LRN and ENC_SEL lines are connected to buttons that will pull
the lines high when pressed. Since the lines do not have internal pull-down
resistors, a 100k
Ω resistor is used to pull the line to ground when not in
use.
VCC
D6
D7
CRT/LRN
ENC_SEL
SER_IO
CONFIRM
TR_PDN
TR_SEL
TR_DATA
GND
D5
D4
D3
LATCH
SEL_BAUD
MODE_IND
D2
D1
D0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
LICAL-TRC-MT
To Transceiver
2.2k
10k
To Processor or PC
To Transceiver
100k
VCC
100k
VCC
Figure 28: MT Series Transcoder Application Circuit