HCS361_11 Datasheet, PDF (6/42 Pages) Microchip Technology – KEELOQ® Code Hopping Encoder incorporates high security,

HCS361
3.0 EEPROM MEMORY
ORGANIZATION
The HCS361 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 crypt key
(word 0) LSb’s
1
KEY_1 64-bit crypt key
(word 1)
2
KEY_2 64-bit crypt key
(word 2)
3
KEY_3 64-bit crypt key
(word 3) MSb’s
4
SYNC_A 16-bit synch counter
5
SYNC_B/ 16-bit synch counter B
SEED_2 or Seed value (word 2)
6
RESERVED Set to 0000H
7
SEED_0 Seed Value
(word 0) LSb’s
8
SEED_1 Seed Value
(word 1) MSb’s
9
SER_0 Device Serial Number
(word 0) LSb’s
10
SER_1 Device Serial Number
(word 1) MSb’s
11
CONFIG Configuration Word
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.
3.2 SYNC_A, SYNC_B
(Synchronization Counter)
This is the 16-bit synchronization value that is used to
create the hopping code for transmission. This value is
incremented after every transmission. Separate syn-
chronization counters can be used to stay synchro-
nized with different receivers.
3.3 SEED_0, SEED_1, and SEED_2
(Seed Word)
The three word (48 bits) seed code will be transmitted
when seed transmission is selected. This allows the sys-
tem designer to implement the Secure Learn feature or
use this fixed code word as part of a different key genera-
tion/tracking process or purely as a fixed code transmis-
sion.
Note:
Since SEED2 and SYNC_B share the
same memory location, Secure Learn and
Independent mode transmission (including
IR mode) are mutually exclusive.
3.4 SER_0, SER_1
(Encoder Serial Number)
SER_0 and SER_1 are the lower and upper words of
the device serial number, respectively. There are 32
bits allocated for the Serial Number and a selectable
configuration bit determines whether 32 or 28 bits will
be transmitted. The serial number is meant to be
unique for every transmitter.
DS40146F-page 6
© 2011 Microchip Technology Inc.