HCS361_11 Datasheet, PDF (5/42 Pages) Microchip Technology – KEELOQ® Code Hopping Encoder incorporates high security,

2.0 DEVICE OPERATION
As shown in the typical application circuits (Figure 2-1),
the HCS361 is a simple device to use. It requires only
the addition of buttons and RF circuitry for use as the
transmitter in your security application. A description of
each pin is described in Table 2-1.
FIGURE 2-1:
VDD
Typical circuits
B0
S0
VDD
B1
S1
LED
S2
DATA
S3
VSS
Two button remote control
VDD
B4 B3 B2 B1 B0
Tx out
S0
VDD
S1
LED
S2
DATA
S3
VSS
Tx out
Five button remote control (Note¹)
Note:
Up to 15 functions can be implemented by pressing
more than one button simultaneously or by using a
suitable diode array.
TABLE 2-1: PIN DESCRIPTIONS
Name
Pin
Number
Description
S0
S1
S2
S3
VSS
DATA
LED
VDD
1 Switch input 0
2 Switch input 1
3 Switch input 2 / Clock pin when in
Programming mode
4 Switch input 3
5 Ground reference
6 Data output pin /Data I/O pin for
Programming mode
7 Cathode connection for LED
8 Positive supply voltage
The HCS361 will wake-up upon detecting a button
press and delay approximately 10 ms for button
debounce (Figure 2-2). The synchronization counter,
© 2011 Microchip Technology Inc.
HCS361
discrimination value and button information will be
encrypted to form the hopping code. The hopping code
portion will change every transmission, even if the
same button is pushed again. A code word that has
been transmitted will not repeat for more than 64K
transmissions. This provides more than 18 years of use
before a code is repeated; based on 10 operations per
day. Overflow information sent from the encoder can be
used to extend the number of unique transmissions to
more than 192K.
If in the transmit process it is detected that a new but-
ton(s) has been pressed, a RESET will immediately
occur and the current code word will not be completed.
Please note that buttons removed will not have any
effect on the code word unless no buttons remain
pressed; in which case the code word will be completed
and the power-down will occur.
FIGURE 2-2:
ENCODER OPERATION
Power-Up
(A button has been pressed)
RESET and Debounce Delay
(10 ms)
Sample Inputs
Update Sync Info
Encrypt With
Crypt Key
Load Transmit Register
Transmit
Yes
Buttons
Added
?
No
All
No
Buttons
Released
?
Yes
Complete Code
Word Transmission
Stop
DS40146F-page 5