User's Manual

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THEORY OF OPERATION
The MS Series Keyfob Transmitter combines a high-performance synthesized
transmitter with an on-board MS Series encoder IC to form a highly reliable, yet
cost-effective RF remote control transmitter. The transmitter’s synthesized
architecture delivers superior stability and frequency accuracy while minimizing
the effects of temperature and body proximity.
The advanced MS Series encoder has several advantages over previous
solutions. It provides more security by offering 2
24
addresses, which is several
orders of magnitude greater than older encoders. Furthermore, the address is
instantly established with a simple button press, eliminating cumbersome DIP
switches and cut traces. When paired with a MS Series decoder, keyfob identity
can be determined and distinct transmitter-receiver relationships established.
The keyfob operates in the following manner: when a button is pressed on the
keyfob, power is applied to the internal circuitry and the encoder IC is enabled.
The encoder then detects the logic states of the button data lines. The encoder
data is used to modulate the transmitter, which, through the antenna, conveys
the data into free space. The transmission cycle continues until the button is
released. On the receiver side, a MS Series decoder IC is used to check the
transmitter’s address bits against the address saved in memory. If a match is
confirmed, and if the decoder has permission to recognize the specific button
being pressed, the decoder’s outputs are set to replicate the transmitter’s button
states. These outputs can then be used to activate external circuitry required by
the application.
The transmitter is compatible with the LC and LR product families. For
applications where range is critical, the LR Series receiver is the best choice due
to its outstanding sensitivity. When the keyfob transmitter is combined with an LR
Series receiver and the MS Series decoder chip, ranges up to 1,000 feet are
possible. Applications operating over shorter distances will also benefit from the
increased link reliability and superior noise immunity provided by the LR receiver.
SETTING THE TRANSMITTER ADDRESS
The encoder address is set by using a
paper clip to press the
CREATE_ADDR button on the board
through the hole in the back of the
case. When the button is depressed,
an LED on the board will light up
indicating that the address is being
created. The address will be
randomized for as long as the button is
held down. When the button is
released, the address is stored in
memory and the LED will begin flashing
to indicate that the Control Permissions may now be set. Press the buttons that
the transmitter will have the authority to access. Press the CREATE_ADDR
button with the paper clip again or wait 17 seconds for it to time out and the
address is set. The decoder will need to learn the address before it will accept
any transmissions. Please see the Typical Applications section of this data guide
or the MS Series Decoder Data Guide for details on learning an address.
BUTTON ASSIGNMENTS
The keyfob is available in five unique button configurations. Those configurations
and the corresponding switch numbers are shown in the figure below. The table
shows which encoder data line has been assigned to each switch. When a
button is pressed, the data line will go high, causing the corresponding data line
on the decoder to go high if the addresses match.
S4
S2
S1
S3S5
S5
S2
S5
S4
S4
S2
S4
S1
S3
S2
Figure 3: OTX-***-HH-KF#-MS Button Assignments
Figure 2: CREATE_ADDR Button Access
Button Data Line
S1 D0
S2 D1
S3 D2
S4 D3
S5 D4
ELECTRICAL SPECIFICATIONS
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POWER SUPPLY
Operating Voltage V
CC
2.1 3.0 3.6 VDC
–
Supply Current I
CC
–
3.4
–
mA
–
Power-down Current I
PDN
–
5.0
–
nA
1
TRANSMITTER SECTION
Transmit Frequency Range F
C
OTX-315-HH-KF#-MS
–
315
–
MHz
–
OTX-418-HH-KF#-MS
–
418
–
MHz
–
OTX-433-HH-KF#-MS
– 433.92 –
MHz
–
Center Frequency Accuracy
–
-50
–
+50 kHz
–
Data Rate – – 9600 – bps –
ENVIRONMENTAL
Operating Temperature Range – -40 – +85
°C1
1. Characterized, but not tested.
Notes
CREATE_ADDR
Button Access