HCS410-IST MICROCHIP [Microchip Technology], HCS410-IST Datasheet - Page 24

• Manufacturer Part Number: HCS410-IST
• Manufacturer: MICROCHIP [Microchip Technology]

HCS410
4.3
In a typical decoder operation (Figure 4-4), the key
generation on the decoder side is done by taking the
serial number from a transmission and combining that
with the manufacturer’s code to create the same
encoder key that is stored in the HCS410. Once the
encoder key is obtained, the rest of the transmission
can be decrypted. The decoder waits for a transmission
and immediately checks the serial number to determine
if it is a learned transmitter. If it is, the code hopping por-
tion of the transmission is decrypted using the stored
key. It uses the discrimination bits to determine if the
decryption was valid. If everything up to this point is
valid, the synchronization counter value is evaluated.
DS40158E-page 24
CH Mode Decoder Operation
Preliminary
FIGURE 4-4:
No
No
No
No
No
Decrypt Transmission
in Temp Location
Serial Number
Save Counter
Transmission
Decryption
Within 32K
Received
Within 16
Counter
Counter
Match
Does
Start
Valid
TYPICAL CH MODE
DECODER OPERATION
Is
Is
?
?
?
?
Is
?
Yes
Yes
Yes
No
Yes
 2001 Microchip Technology Inc.
Yes
Command
Execute
Counter
Update
and