HCS320_11 Datasheet, PDF (5/38 Pages) Microchip Technology – KEELOQ® Code Hopping Encoder Automatic code word completion

2.0 DEVICE OPERATION
As shown in the typical application circuits (Figure 2-1),
the HCS320 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:
TYPICAL CIRCUITS
+12V
R ⁽²⁾
B0
S0
VDD
B1
S1
LED
S2
PWM
Tx out
SHIFT VSS
2 button remote control
+12V
SHIFT B3 B2 B1 B0
R ⁽²⁾
S0
VDD
S1
LED
S2
PWM
SHIFT VSS
Tx out
5 button remote control⁽¹⁾
Note 1: The full 16 function codes are
implemented using the shift button.
2: Resistor R is recommended for current
limiting.
HCS320
TABLE 2-1: PIN DESCRIPTIONS
Name
Pin
Number
Description
S0
1 Switch input 0
S1
2 Switch input 1
S2
3 Switch input 2/Clock pin when in
Programming mode
SHIFT 4 Switch input for Shift
VSS
5 Ground reference
PWM
6 Pulse Width Modulation (PWM)
output pin / Data pin for
Programming mode
LED
7 Cathode connection for LED
VDD
8 Positive supply voltage
The HCS320 will wake-up upon detecting a button
press and delay approximately 10 ms for button
debounce (Figure 2-2). The synchronization counter,
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.
© 2011 Microchip Technology Inc.
DS41097D-page 5