hcs301 Microchip Technology Inc., hcs301 Datasheet - Page 5

• Manufacturer Part Number: hcs301
• Description: Keeloq Code Hopping Encoder
• Manufacturer: Microchip Technology Inc.

2.0
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.
FIGURE 2-1:
Note:
2001 Microchip Technology Inc.
Note 1:
B4 B3 B2 B1 B0
5 button remote control
2 button remote control
DEVICE OPERATION
2:
B0
B1
When V
tive loads, a resistor with a minimum value
of 50
This prevents clamping of PWM at 9.0V in
the event of PWM overshoot.
more than one button simultaneously or by using a
suitable diode array.
+12V
Up to 15 functions can be implemented by pressing
Resistor R is recommended for current limiting.
R
(2)
DD
should be used in line with V
S0
S0
S1
S2
S3
S1
S2
S3
TYPICAL CIRCUITS
> 9.0V and driving low capaci-
(1)
PWM
PWM
V
V
V
V
LED
LED
SS
SS
DD
DD
+12V
R
(2)
Tx out
Tx out
DD
.
TABLE 2-1:
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.
Name
PWM
LED
V
V
S0
S1
S2
S3
DD
SS
Number
Pin
1
2
3
4
5
6
7
8
PIN DESCRIPTIONS
Switch input 0
Switch input 1
Switch input 2 / Clock pin when in
Programming mode
Switch input 3
Ground reference
Pulse Width Modulation (PWM)
output pin / Data pin for
Programming mode
Cathode connection for LED
Positive supply voltage
Description
HCS301
DS21143B-page 5