HCS362-I Datasheet, PDF (13/38 Pages) Microchip Technology – KEELOQ Code Hopping Encoder

3.3 Seed Code Word Data Format
A seed transmission transmits a code word that con-
sists of 60 bits of fixed data that is stored in the
EEPROM. This can be used for secure learning of
encoders or whenever a fixed code transmission is
required. The seed code word further contains the
function code and the status information (VLOW, CRC
and QUEUE) as configured for normal code hopping
code words. The seed code word format is shown in
Figure 3-9. The function code for seed code words is
always ‘1111b’.
FIGURE 3-9: SEED CODE WORD FORMAT
With QUEN = 1
Fixed Portion
(9 bits)
QUE CRC VLOW BUT
(2 bits) (2 bits) (1-bit) (4 bits)
Q1 Q0 C1 C0 S2 S1 S0 S3
HCS362
Seed code words can be configured as follows:
• Enabled permanently.
• Disabled permanently.
• Enabled until the synchronization counter is
greater than 7Fh, this configuration is often
referred to as Limited Seed.
• The time before the seed code word is transmitted
can be set to 1.6 s or 3.2 s, this configuration is
often referred to as Delayed Seed. When this
option is selected, the HCS362 will transmit a
code hopping code word for 1.6 s or 3.2 s, before
the seed code word is transmitted.
SEED Code
(60 bits)
SEED
Transmission Direction LSB First
3.3.1 SEED OPTIONS
The button combination (S[3210]) for transmitting a
Seed code word can be selected with the Seed and
SeedC (SEED[0..1] and SEEDC) configuration
options as shown in Table 3-1 and Table 3-2:
TABLE 3-1: SEED OPTIONS (SEEDC = 0)
SEED
00
01
10
11
Note:
Seed
S[3210]
-
0101*
0101
0101
*Limited Seed
1.6 s Delayed Seed
S[3210]
-
0001*
0001
-
TABLE 3-2: SEED OPTIONS (SEEDC = 1)
SEED
00
01
10
11
Note:
Seed
S[3210]
-
1001*
1001
1001
*Limited Seed
3.2 s Delayed Seed
S[3210]
-
0011*
0011
-
Example A): Selecting SEEDC = 1 and SEED = 11:
makes SEED transmission available every time the
combination of buttons S3 and S0 is pressed simulta-
neously, but Delayed Seed mode is not available.
Example B): Selecting SEEDC = 0 and SEED = 01:
makes SEED transmission available only for a limited
time (only up to 128 times). The combination of buttons
S2 and S0 produces an immediate transmission of the
SEED code. Pressing and holding for more than 1.6
seconds the S0 button alone, produces the SEED code
word transmission (Delayed Seed).
© 2002 Microchip Technology Inc.
Preliminary
DS40189D-page 13