RFHCS362G_11 Datasheet, PDF (13/54 Pages) Microchip Technology – KEELOQ® Code Hopping Encoder with UHF ASK/FSK Transmitter

rfHCS362G/362F
3.1 Transmission Modulation Format
The rfHCS362 transmission is made up of several code
words. Each code word consists of a preamble, a
header and data (see Figure 3-2).
The code words are separated by a Guard Time that
can be set to 0 ms, 6.4 ms, 25.6 ms or 76.8 ms with the
Guard Time Select (GUARD[0..1]) configuration
option. All other timing specifications for the modulation
formats are based on a basic timing element (TE). This
Timing Element can be set to 100 μs, 200 μs, 400 μs
or 800 μs with the Baud Rate Select (BSEL[0..1])
configuration option. The Header Time can be set to
3 TE or 10 TE with the Header Select (HEADER) config-
uration option.
There are two different modulation formats available on
the rfHCS362 that can be set using the Modulation
Select (MOD) configuration option:
• Pulse Width Modulation (PWM)
• Manchester Encoding
Modulation formats are shown in Figure 3-3 and
Figure 3-4. Code word data formats are shown in
Figure 3-6.
FIGURE 3-2: CODE WORD TRANSMISSION SEQUENCE
1 CODE WORD
Preamble Header Encrypt
Fixed
Guard
Preamble Header Encrypt
FIGURE 3-3: PULSE WIDTH MODULATION TRANSMISSION FORMAT
LOGIC "0"
LOGIC "1"
1
16
TE TE TE
TBP
31 TE Preamble
3/10
TE
Header
Encrypted
Portion
Fixed Code
Portion
Guard
Time
FIGURE 3-4: MANCHESTER TRANSMISSION FORMAT
12
START bit
bit 0 _{bit 1} bit 2
16
TE TE
LOGIC "0"
LOGIC "1"
TBP
STOP bit
Preamble Header
Encrypted
Portion
Fixed Code
Portion
Guard
Time
© 2011 Microchip Technology Inc.
DS41189B-page 13