HCS301_11 Datasheet, PDF (5/38 Pages) Microchip Technology – Microchip Technology Inc. is a code hopping encoder designed for secure

2.0 DEVICE OPERATION
As shown in the typical application circuits (Figure 2-1),
the HCS301 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 given in Table 2-1.
Note:
When VDD > 9.0V and driving low capaci-
tive loads, a resistor with a minimum value
of 50Ω should be used in line with VDD.
This prevents clamping of PWM at 9.0V in
the event of PWM overshoot.
FIGURE 2-1:
+12V
TYPICAL CIRCUITS
R ⁽²⁾
B0
S0
VDD
B1
S1
LED
S2
PWM
S3
VSS
Tx out
2 button remote control
B4 B3 B2 B1 B0
+12V
R ⁽²⁾
S0
VDD
S1
LED
S2
PWM
S3
VSS
5 button remote control ⁽¹⁾
Tx out
Note 1: Up to 15 functions can be implemented by pressing
more than one button simultaneously or by using a
suitable diode array.
2: Resistor R is recommended for current limiting.
HCS301
TABLE 2-1: PIN DESCRIPTIONS
Name
Pin
Number
Description
S0
S1
S2
S3
VSS
PWM
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 Pulse Width Modulation (PWM)
output pin / Data pin for
Programming mode
7 Cathode connection for LED
8 Positive supply voltage
The HCS301 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.
DS21143C-page 5