hcs320 Microchip Technology Inc., hcs320 Datasheet - Page 10

• Manufacturer Part Number: hcs320
• Description: Keeloq Code Hopping Encoder
• Manufacturer: Microchip Technology Inc.

HCS320
4.3
Synchronous Transmission mode can be used to clock
the code word out using an external clock.
To enter Synchronous Transmission mode, the Pro-
gramming mode start-up sequence must be executed
as shown in Figure 4-3. If either S1 or S0 is set on the
falling edge of S2, the device enters Synchronous
Transmission mode. In this mode, it functions as a nor-
mal transmitter, with the exception that the timing of the
PWM data string is controlled externally and 16 extra
bits are transmitted at the end with the code word.
FIGURE 4-3:
FIGURE 4-4:
DS41097C-page 10
MSb
PWM
S2
S[1:0]
Reserved
(16 bits)
Synchronous Transmission Mode
T
PS
T
PH
Padding
(2 bits)
1 T
SYNCHRONOUS TRANSMISSION MODE
CODE WORD ORGANIZATION (SYNCHRONOUS TRANSMISSION MODE)
PH
“01,10,11”
2
Fixed Portion
Function
(4-bit)
Code
t = 50ms
Serial Number
(28 bits)
The button code will be the S0, S1 value at the falling
edge of S2. The timing of the PWM data string is con-
trolled by supplying a clock on S2 and should not
exceed 20 kHz. The code word is the same as in PWM
mode with 16 reserved bits at the end of the word. The
reserved bits can be ignored. When in Synchronous
Transmission mode S2 should not be toggled until all
internal processing has been completed as shown in
Figure 4-4.
Preamble
Function
(4-bit)
Code
Header
Encrypted Portion
DISC+ OVR
(12 bits)
2001 Microchip Technology Inc.
82 Data bits
Transmitted
LSb first.
Sync Counter
(16 bits)
Data
LSb