–

–

–

–

10

11

Latch Mode

The MS Series decoder has two output options based on the state of the

LATCH line. If it is low, then the data lines are momentary, meaning that

they are only high for as long as a valid signal is received. Once the signal

stops and the decoder times out, the lines are pulled low.

If the LATCH line is high, the decoder pulls a data line high upon reception

of a valid signal and holds it high until the signal is received a second time,

at which point the decoder pulls it low. The decoder must see a break and

time out between valid transmissions before it toggles the outputs. The

minimum required time-out periods are listed in the Receive Mode section.

Receiver Control Mode

If the RX_CNTL line is pulled high when the decoder initially powers on,

then the decoder enters Receiver Control Mode. Once in this mode, the

RX_CNTL line becomes an output that can be attached to the PDN or

V

the decoder to power down the receiver when it is not required, thereby

reducing current consumption and prolonging battery life. The decoder

draws full current in this mode, but an active receiver typically draws much

more than the decoder, so a savings is realized.

The decoder activates the receiver for approximately one packet’s time plus

10ms for the receiver to power up, so the actual “on” time depends on the

baud rate chosen by the user. This time can be calculated in milliseconds

as (60/Baud Rate)(1000) + 10. The “off” time is nine times the “on” time,

resulting in a 10% duty cycle, greatly reducing the receiver’s current

consumption. However, there may be a lag time from when the encoder

activates to when the decoder responds. The decoder enters Receive

Mode when it sees a valid packet, so there would only be a lag for the first

packet. This can be reduced by selecting a higher baud rate.

If this feature is not going to be used, then this pin should be tied to

ground. If it is tied to V

the line to ground while trying to power down the receiver. This mode is

appropriate for receivers that have a high internal pull-up resistance, such

as those offered by Linx. If the intended receiver does not have a pull-up,

then a 100k

Ω or larger resistor to V

activate this mode.

TX ID

The TX_ID line outputs an eight-bit binary number to identify which learned

encoder sent the transmission. The number is output at the baud rate

set by the SEL_BAUD lines and normally corresponds to the order in

which the decoder learned the encoder, so the first encoder learned gets

number ‘1’, the second gets number ‘2’, and so on. An exception arises

when the memory is full, in which case the first numbers are overwritten as

described in the Learn Mode section. Application Note AN-00156 shows

some example software to read the TX_ID and associate it with a particular

encoder. The C and Visual Basic code is well documented so that it can be

modified for a specific application.

System Example

The first step in using the decoder is to set the baud rate and determine

if the outputs should be latched or momentary. Next, the decoder needs

to learn the encoder’s Address. This is done by momentarily pressing the

button connected to the LEARN line. The LED connected to the MODE_

IND line begins to flash to indicate that the decoder is ready to learn a new

Address. One of the buttons on the transmitter is pressed to send a signal

to the decoder. Once this is done, the LEARN button is pressed again to

exit Learn Mode.

Now, when a button is pressed on the encoder, the corresponding line on

the decoder activates. If the LATCH line is high, the data line remains high

until the encoder button is pressed again, telling the decoder to pull the line

low.

To clear the decoder's memory, the LEARN button is pressed and held

for ten seconds until the MODE_IND line goes low. Once the button is

released, the LED lights for two seconds to indicate that the memory has

been cleared.