hcs412 Microchip Technology Inc., hcs412 Datasheet - Page 13
hcs412
Manufacturer Part Number
hcs412
Description
Keeloq? Code Hopping Encoder And Transponder
Manufacturer
Microchip Technology Inc.
Datasheet
1.HCS412.pdf
(44 pages)
Available stocks
Company
Part Number
Manufacturer
Quantity
Price
Part Number:
hcs412-I/SN
Manufacturer:
MICROCHI
Quantity:
20 000
FIGURE 3-5:
FIGURE 3-6:
3.4
3.4.1
The code word completion feature ensures that entire
code words are transmitted, even if the active button is
released before the code word transmission is com-
plete. If the button is held down beyond the time for one
code word, multiple complete code words will result.
The device default is that a momentary button press
will transmit at least one complete code word. Enable
the Minimum Four Code Words (MTX4) configuration
option to extend this feature such that a minimum of 4
code words are completed on a momentary button acti-
vation.
2002 Microchip Technology Inc.
TOTAL TRANSMISSION:
TOTAL TRANSMISSION:
Encoder Special Features
CODE WORD COMPLETION AND
MINIMUM CODE WORDS
31 RFT
50% Duty
Preamble
Long Preamble (LPRE) disabled
PWM TRANSMISSION FORMAT—MOD = 0
MANCHESTER TRANSMISSION FORMAT—MOD = 1
E
Preamble, 50% Duty Cycle
START bit
Header
bit 0 bit 1 bit 2
Preamble Sync Encrypt
Preamble
Encrypted
Portion
LOGIC "0"
LOGIC "1"
Sync
Preliminary
Header
1 CODE WORD
10T
CODE WORD
Encrypt
1 CODE WORD
E
LOGIC "0"
LOGIC "1"
CODE WORD
Fixed
Fixed
3.4.2
The Auto-shutoff function prevents battery drain should
a button get stuck for a long period of time. The time
period (T
the device will enter Time-out mode.
The device will stop transmitting in Time-out mode but
there will be leakage across the stuck button input’s
internal pull-down resistor. The current draw will there-
fore be higher than when in Standby mode.
3.4.3
Federal Communications Commission (FCC) part 15
rules specify the limits on worst case average funda-
mental power and harmonics that can be transmitted in
a 100 ms window. For FCC approval purposes, it may
therefore be advantageous to minimize the transmis-
sion duty cycle. This can be achieved by minimizing the
on-time of the individual bits as well as by blanking out
consecutive code words.
T
Encrypted
E
Portion
Fixed Code
T
T
Portion
E
Guard
E
Guard
AUTO-SHUTOFF
CODE WORD BLANKING ENABLE
TO
T
T
E
E
) is approximately 20 seconds, after which
Preamble
Preamble Sync
STOP bit
Fixed Code
Sync
Portion
Encrypt
Guard
Time
Encrypt
HCS412
DS41099C-page 13
Guard
Time