HCS301-IP Microchip Technology, HCS301-IP Datasheet - Page 4

• Manufacturer Part Number: HCS301-IP
• Description: KEELOQ CODE HOPPING ENCODER
• Manufacturer: Microchip Technology

HCS301
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 described in Table 2-1.
FIGURE 2-1:
TABLE 2-1:
DS21143A-page 4
Name
PWM
LED
V
V
Note:
S0
S1
S2
S3
Note 1:
DD
SS
(Note 2)
B4 B3 B2 B1 B0
2:
DEVICE OPERATION
Number
B0
B1
When V
loads, a resistor with a minimum value of 50
should be used in line with V
clamping of PWM at 9.0V in the event of PWM
overshoot.
R
Pin
Up to 15 functions can be implemented by pressing
more than one button simultaneously or by using a
suitable diode array.
Resistor (R) is recommended for current limiting.
1
2
3
4
5
6
7
8
V
+12V
DD
5 button remote control (Note1)
TYPICAL CIRCUITS
PIN DESCRIPTIONS
DD
pin when in programming mode
programming mode
Ground reference connection
output pin/Data pin for
programming mode
Cathode connection for directly
driving LED during transmission
Positive supply voltage
connection
Switch input 0
Switch input 1
Switch input 2/Can also be clock
Switch input 3/Clock pin when in
Pulse width modulation (PWM)
2 button remote control
S0
S0
S1
S2
S3
S1
S2
S3
> 9.0V and driving low capacitive
(Note 2)
PWM
PWM
V
V
V
V
LED
LED
V
SS
SS
DD
Description
DD
DD
R
+12V
DD
. This prevents
Tx out
Tx out
Preliminary
The high security level of the HCS301 is based on the pat-
ented K
length of 32 bits and a key length of 64 bits is used. The
algorithm obscures the information in such a way that even
if the transmission information (before coding) differs by
only 1 bit from the information in the previous transmis-
sion, the next coded transmission will be totally different.
Statistically, if only 1 bit in the 32-bit string of information
changes, approximately 50 percent of the coded transmis-
sion will change. The HCS301 will wake up upon detecting
a switch closure and then delay approximately 10 ms for
switch debounce (Figure 2-2). The synchronization infor-
mation, 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, even if the same button is pushed again. 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 opera-
tions per day. Overflow information sent from the encoder
can be used by the decoder 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 be
forced and the 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 this case,
the code word will be completed and the power down will
occur.
FIGURE 2-2:
EE
L
OQ
Yes
technology. A block cipher based on a block
Reset and Debounce Delay
Load Transmit Register
(A button has been pressed)
ENCODER OPERATION
Word Transmission
Update Sync Info
Complete Code
Encryption Key
Sample Inputs
Encrypt With
Released?
Power Up
Buttons
Added?
Buttons
Transmit
Stop
(10 ms)
1996 Microchip Technology Inc.
All
Yes
No
No