hcs362 Microchip Technology Inc., hcs362 Datasheet - Page 9

• Manufacturer Part Number: hcs362
• Description: Keeloq Code Hopping Encoder
• Manufacturer: Microchip Technology Inc.

3.1
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 (
option. All other timing specifications for the modulation
formats are based on a basic timing element (T
Timing Element can be set to 100 s, 200 s, 400 s
or 800 s with the Baud Rate Select (
FIGURE 3-2:
FIGURE 3-3:
FIGURE 3-4:
2002 Microchip Technology Inc.
Preamble
Transmission Modulation Format
1
1 2
Preamble
CODE WORD TRANSMISSION SEQUENCE
TRANSMISSION FORMAT (PWM)
TRANSMISSION FORMAT (MANCHESTER)
Header
GUARD
16
31 T
START bit
Header
1 CODE WORD
E
Preamble
[
0..1
Encrypt
bit 0 bit 1 bit 2
]) configuration
BSEL
Encrypted
Portion
[
Fixed
E
0..1
). This
16
Header
Preliminary
3-10
T
])
E
Guard
Encrypted
Portion
configuration option. The Header Time can be set to
3 T
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.
E
Fixed Code
or 10 T
Portion
Preamble
E
with the Header Select (HEADER) Con-
LOGIC "0"
LOGIC "1"
Fixed Code
Portion
STOP bit
LOGIC "0"
LOGIC "1"
Header
Guard
Time
T
HCS362
E
T
Encrypt
Guard
Time
E
T
T
T
BP
DS40189D-page 9
BP
E
T
E
T
E