RFHCS362F Datasheet, PDF (13/60 Pages) Microchip Technology – Code Hopping Encoder with UHF ASK/FSK Transmitter

3.0 ENCODER OPERATION
The rfHCS362G/362F will wake-up upon detecting a
switch closure and then delay for switch debounce
(Figure 3-1). The synchronization information, fixed
information and switch information will be encrypted to
form the hopping code. The encrypted or hopping code
portion of the transmission will change every time a
button is pressed, even if the same button is pushed
again. Keeping a button pressed for a long time will
result in the same code word being transmitted until the
button is released or time-out occurs.
The time-out time can be selected with the time-out
(TIMOUT[0..1]) configuration option. This option
allows the time-out to be disabled or set to 0.8 s, 3.2 s
or 25.6 s. When a time-out occurs, the device will go
into SLEEP mode to protect the battery from draining
when a button gets stuck.
If in the transmit process, and a new button is pressed,
the current code word will be aborted. A new code word
will be transmitted and the time-out counter will RESET.
If all the buttons are released, the minimum code words
will be completed. The minimum code words can be set
to 1, 2, 4 or 8 using the Minimum Code Words
(MTX[0..1]) configuration option. If the time for trans-
mitting the minimum code words is longer than the
time-out time, the device will not complete the minimum
code words.
Note:
If multiple buttons are pressed and one
is released, it will not have any effect
on the code word. If no buttons remain
pressed the minimum code words will
be completed and the power-down will
occur.
A code that has been transmitted will not occur again
for more than 64K transmissions. This will provide
more than 18 years of typical use before a code is
repeated based on 10 operations per day. Overflow
information programmed into the encoder can be used
by the decoder to extend the number of unique trans-
missions to more than 192K.
rfHCS362G/362F
FIGURE 3-1: BASIC FLOW DIAGRAM OF
THE DEVICE OPERATION
START
Sample Buttons
Get Config.
Seed
Yes
TX?
No
Increment
Counter
Read
Seed
Encrypt
Transmit
Yes
Time-out
No
No
MTX
STOP
Yes
No
Buttons
Yes
No
Seed ^Yes Seed
Yes
Time
Button
No
No
No
New
Buttons
Yes
© 2002 Microchip Technology Inc.
Preliminary
DS41189A-page 13