HCS201_11 MICROCHIP [Microchip Technology], HCS201_11 Datasheet - Page 11

• Manufacturer Part Number: HCS201_11
• Manufacturer: MICROCHIP [Microchip Technology]

5.0
5.1
The code word completion feature ensures that entire
code words are transmitted, even if the button is
released before the code word is complete. If the but-
ton is held down beyond the time for one code word,
multiple code words will result. If another button is acti-
vated during a transmission, the active transmission
will be aborted and a new transmission will begin using
the new button information.
5.2
The V
(Figure 9-4) and will be transmitted as a one if the
operating voltage has dropped below the low voltage trip
point. The trip point is selectable based on the battery
voltage being used. See Section 3.7.2 for a description
of how the low voltage select option is set. This V
signal is transmitted so the receiver can give an audible
signal to the user that the transmitter battery is low.
5.3
The auto-shutoff function automatically stops the device
from transmitting if a button inadvertently gets pressed
for a long period of time. This will prevent the device from
draining the battery if a button gets pressed while the
transmitter is in a pocket or purse. Time-out period is T
5.4
In order to increase the level of security in a system, it
is possible for the receiver to implement what is known
as a secure learn function. This can be done by utilizing
the seed value stored in EEPROM, transmitted only
when all three button inputs are pressed at the same
time (Table 5-1). Instead of the normal key generation
inputs being used to create the crypt key, this seed
value is used.
FIGURE 5-1:
© 2011 Microchip Technology Inc.
LOW
BRS = 0
BRS = 1
SPECIAL FEATURES
Code Word Completion
V
Auto-Shutoff
Seed Transmission
LOW
bit is transmitted with every transmission
: Voltage LOW Indicator
BLANK ALTERNATE CODE WORD (BACW)
Amplitude
2A
A
Code Word
LOW
TO
.
Code Word
TABLE 5-1:
5.5
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
duty cycle of the individual bits as well as by blanking
out consecutive code words. Blank Alternate Code
Word (BACW) may be used to reduce the average
power of a transmission by transmitting only every sec-
ond code word (Figure 5-1). This is a selectable feature
that is determined in conjunction with the baud rate
selection bit BSL0.
Enabling the BACW option may likewise allow the user
to transmit a higher amplitude transmission as the time
averaged power is reduced. BACW effectively halves
the RF on time for a given transmission so the RF out-
put power could theoretically be doubled while main-
taining the same time averaged output power.
Hopping Code
Seed Code
Standby
Time
Blank Alternate Code Word
Code Word
PIN ACTIVATION TABLE
Function
0
1
2
5
6
7
-
Code Word
HCS201
S2
0
0
0
1
1
1
-
DS41098D-page 11
S1
0
0
1
0
1
1
-
S0
0
1
0
1
0
1
-