hcs410 Microchip Technology Inc., hcs410 Datasheet - Page 9

• Manufacturer Part Number: hcs410
• Description: Keeloq Code Hopping Encoder And Transponder Keeloq Code Hopping Encoder And Transponder
• Manufacturer: Microchip Technology Inc.

2.2.2
The Data Modulation Format is selectable between
Pulse Width Modulation (PWM) format and Manches-
ter encoding. Both formats are preceded by a preamble
and synchronization header, followed by the 69-bits of
data. Manchester encoding has a leading and closing
‘1’ for each code word.
FIGURE 2-10: TRANSMISSION FORMAT—MANCH = 0
FIGURE 2-11: TRANSMISSION FORMAT—MANCH = 1
 2001 Microchip Technology Inc.
TOTAL TRANSMISSION:
1
CODE WORD:
TOTAL TRANSMISSION:
1 2
TRANSMISSION DATA MODULE
2
CODE WORD:
4
4 5 6
5
T
E
T
Preamble
6
E
Preamble
LOGIC "0"
LOGIC "1"
Preamble
LOGIC "0"
LOGIC "1"
Sync
Preamble Sync Encrypt
14 15 16
14 15 16
1 CODE WORD
Encrypt
1
2
1
Preliminary
3 5 7 9
Sync
2
4 6 8 10
Sync
3
Fixed
CODE WORD
Code Word
4
1 CODE WORD
Start bit
Guard
The same code word is continuously sent as long as
the input pins are kept high with a guard time separat-
ing the code words. All of the timing values are in mul-
tiples of a Basic Timing Element (T
changed using the baud rate option bits.
Encrypted
Fixed
Encrypted
Data
TX Data
Preamble
Guard
Sync
Preamble Sync Encrypt
Encrypt
BIT
Fixed Code
Fixed Code
T
T
E
Data
E
Data
HCS410
Stop bit
E
DS40158E-page 9
), which can be
Guard
Time
Guard
Time