hcs301 Microchip Technology Inc., hcs301 Datasheet - Page 12

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

HCS301
5.7
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-
FIGURE 5-1:
DS21143B-page 12
(1 out of 4 transmitted)
(1 out of 2 transmitted)
(All words transmitted)
BACW Enabled
BACW Disabled
BACW Enabled
Blank Alternate Code Word
BLANK ALTERNATE CODE WORD (BACW)
2A
4A
Amplitude
A
Code Word
Code Word
Time
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.
Code Word
2001 Microchip Technology Inc.
Code Word