HCS410_01 Datasheet, PDF (9/36 Pages) Microchip Technology – KEELOQ® Code Hopping Encoder and Transponder

HCS410
2.2.2 TRANSMISSION DATA MODULE
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.
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 (TE), which can be
changed using the baud rate option bits.
FIGURE 2-10: TRANSMISSION FORMAT—MANCH = 0
TOTAL TRANSMISSION:
1 CODE WORD
Preamble Sync Encrypt Fixed
Guard Preamble Sync Encrypt
CODE WORD:
TE
LOGIC "0"
BIT
LOGIC "1"
TE
12 45 6
Preamble
13579
14 15 16 2 4 6 8 10
Sync
Code Word
Encrypted
TX Data
Fixed Code
Data
Guard
Time
FIGURE 2-11: TRANSMISSION FORMAT—MANCH = 1
TOTAL TRANSMISSION:
1 CODE WORD
Preamble Sync Encrypt Fixed
Guard Preamble Sync Encrypt
TE
CODE WORD:
LOGIC "0"
LOGIC "1"
TE
12
456
Preamble
Start bit
13
14 15 16 ^{2 4}
Sync
Encrypted
Data
CODE WORD
Stop bit
Fixed Code
Data
Guard
Time
 2001 Microchip Technology Inc.
Preliminary
DS40158E-page 9