HCS362-I Datasheet, PDF (15/38 Pages) Microchip Technology – KEELOQ Code Hopping Encoder

4.0 EEPROM MEMORY
ORGANIZATION
The HCS362 contains 288 bits (18 x 16-bit words) of
EEPROM memory (Table 4-1). This EEPROM array is
used to store the encryption key information and
synchronization value. Further descriptions of the
memory array is given in the following sections.
TABLE 4-1: EEPROM MEMORY MAP
Word
Address
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
Field
KEY1_0
KEY1_1
KEY1_2
KEY1_3
KEY2_0
KEY2_1
KEY2_2
KEY2_3
SEED_0
SEED_1
SEED_2
SEED_3
CONFIG_0
CONFIG_1
SERIAL_0
SERIAL_1
SYNC
RES
Description
64-bit Encryption Key1
(Word 0) LSB
64-bit Encryption Key1
(Word 1)
64-bit Encryption Key1
(Word 2)
64-bit Encryption Key1
(Word 3) MSB
64-bit Encryption Key2
(Word 0) LSB
64-bit Encryption Key2
(Word 1)
64-bit Encryption Key2
(Word 2)
64-bit Encryption Key2
(Word 3) MSB
Seed value (Word 0)
LSB
Seed value (Word 1)
Seed value (Word 2)
Seed value (Word 3)
MSB
Configuration Word
(Word 0)
Configuration Word
(Word 1)
Serial Number
(Word 0) LSB
Serial Number
(Word 1) MSB
Synchronization counter
Reserved – Set to zero
HCS362
4.1 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.
4.2 SYNC (Synchronization Counter)
This is the 16-bit synchronization value that is used to
create the hopping code for transmission. This value
will be incremented after every transmission.
4.3 SEED_0, SEED_1, SEED_2,
and SEED 3 (Seed Word)
This is the four word (60 bits) seed code that will be
transmitted when seed transmission is selected. This
allows the system designer to implement the secure
learn feature or use this fixed code word as part of a dif-
ferent key generation/tracking process or purely as a
fixed code transmission.
Note:
Upper four Significant bits of SEED_3 con-
tains extra configuration information (see
Table 4-4).
4.4 SERIAL_0, SERIAL_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.
© 2002 Microchip Technology Inc.
Preliminary
DS40189D-page 15