HCS362-I Datasheet, PDF (9/38 Pages) Microchip Technology – KEELOQ Code Hopping Encoder

HCS362
3.1 Transmission Modulation Format
The HCS362 transmission is made up of several code
words. Each code word starts with a preamble and a
header, followed by the data (see Figure 3-1 and
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) Con-
figuration option.
There are two different modulation formats available on
the HCS362 that can be set according to the Modula-
tion Select (MOD) configuration option:
• Pulse Width Modulation (PWM)
• Manchester Encoding
The various formats are shown in Figure 3-3 and
Figure 3-4.
FIGURE 3-2: CODE WORD TRANSMISSION SEQUENCE
1 CODE WORD
Preamble Header Encrypt
Fixed
Guard
Preamble Header Encrypt
FIGURE 3-3: TRANSMISSION FORMAT (PWM)
1
16
31 TE Preamble
3-10
TE
Header
Encrypted
Portion
LOGIC "0"
LOGIC "1"
TE TE TE
TBP
Fixed Code
Portion
Guard
Time
FIGURE 3-4: TRANSMISSION FORMAT (MANCHESTER)
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
© 2002 Microchip Technology Inc.
Preliminary
DS40189D-page 9