HCS301_11 Datasheet, PDF (6/38 Pages) Microchip Technology – Microchip Technology Inc. is a code hopping encoder designed for secure

HCS301
FIGURE 2-2:
ENCODER OPERATION
Power-Up
(A button has been pressed)
RESET and Debounce Delay
(10 ms)
Sample Inputs
Update Sync Info
Encrypt With
Crypt Key
Load Transmit Register
Transmit
Yes
Buttons
Added
?
No
All
No
Buttons
Released
?
Yes
Complete Code
Word Transmission
Stop
3.0 EEPROM MEMORY
ORGANIZATION
The HCS301 contains 192 bits (12 x 16-bit words) of
EEPROM memory (Table 3-1). This EEPROM array is
used to store the encryption key information,
synchronization value, etc. Further descriptions of the
memory array is given in the following sections.
TABLE 3-1: EEPROM MEMORY MAP
WORD
ADDRESS
MNEMONIC
DESCRIPTION
0
KEY_0 64-bit encryption key
(word 0) LSb’s
1
KEY_1 64-bit encryption key
(word 1)
2
KEY_2 64-bit encryption key
(word 2)
3
KEY_3 64-bit encryption key
(word 3) MSb’s
4
SYNC 16-bit synchronization
value
5
RESERVED Set to 0000H
6
SER_0 Device Serial Number
(word 0) LSb’s
7
SER_1(Note) Device Serial Number
(word 1) MSb’s
8
SEED_0 Seed Value (word 0)
9
SEED_1 Seed Value (word 1)
10
RESERVED Set to 0000H
11
CONFIG Config Word
Note: The MSB of the serial number contains a bit
used to select the Auto-shutoff timer.
3.1 KEY_0 - KEY_3 (64-Bit Crypt Key)
The 64-bit crypt key is used to create the encrypted
message transmitted to the receiver. This key is calcu-
lated and programmed during production using a key
generation algorithm. The key generation algorithm
may be different from the KEELOQ algorithm. Inputs to
the key generation algorithm are typically the transmit-
ter’s serial number and the 64-bit manufacturer’s code.
While the key generation algorithm supplied from
Microchip is the typical method used, a user may elect
to create their own method of key generation. This may
be done providing that the decoder is programmed with
the same means of creating the key for
decryption purposes.
DS21143C-page 6
© 2011 Microchip Technology Inc.