HCS301 Datasheet, PDF (8/20 Pages) Microchip Technology – KEELOQ CODE HOPPING ENCODER

HCS301
FIGURE 4-1: CODE WORD TRANSMISSION FORMAT
LOGIC ‘0’
Bit
Period
LOGIC ‘1’
Preamble
TP
Header
TH
Encrypted Portion
of Transmission
THOP
Fixed Portion of
Transmission
TFIX
Guard
Time
TG
FIGURE 4-2: CODE WORD ORGANIZATION
Fixed Code Data
Repeat VLOW
(1 bit) (1 bit)
Button
Status
(4 bits)
28-bit
Serial Number
Encrypted Code Data
Button
Status
(4 bits)
Discrimina-
tion bits
(12 bits)
16-bit
Sync Value
1 bit of Status
1 bit Fixed
+
Serial Number and
Button Status (32 bits)
+
32 bits of Encrypted Data
66 bits
of Data
Transmitted
FIGURE 4-3: SYNCHRONOUS TRANSMISSION MODE
t = 50 ms
PWM
S2(S3)
S[1:0]
“01,10,11”
FIGURE 4-4:
Reserved
16
TRANSMISSION WORD FORMAT DURING SYNCHRONOUS TRANSMISSION MODE
Padding
2
Button
Code
4
Serial Number
28
Data Word
16
Sync Counter
16
DS21143A-page 8
Preliminary
Transmission Direction
© 1996 Microchip Technology Inc.