hcs370 Microchip Technology Inc., hcs370 Datasheet - Page 13

• Manufacturer Part Number: hcs370
• Description: Keeloq Code Hopping Encoder
• Manufacturer: Microchip Technology Inc.

3.3
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 is identified by the func-
tion bits = 1111
status information (V
Seed code word format is shown in Figure 3-3. The
function code for seed code words is always 1111
Seed code words for Encoder 1 and Encoder 2 can be
configured as follows:
• Enabled with the Seed Button Code (SDBT) con-
• If the Limited Seed (SDLM) configuration option is
• The delay before the seed transmission is sent
FIGURE 3-3:
2002 Microchip Technology Inc.
figuration option, or disabled if SDBT = 0000
set, seed transmissions will be disabled when the
synchronization counter is bigger than 127. Seed
transmissions remain disabled even if the 16/20-
bit counter rolls over to 0.
can be set to 0.0s, 0.8s, 1.6s and 3.2s with the
Seed Time (SDTM) configuration option. When
SDTM is set to a value other than 0.0s, the
HCS370 will transmit a code hopping transmis-
sion until the selected time expires. After the
selected time expires, the seed code words are
transmitted. This is useful for the decoder to learn
With QUEN = 1
Q1 Q0 C1 C0
(2 Bits)
QUE
Open Portion (Not Encrypted)
Seed Code Word Data Format
(2 Bits)
CRC
2
. The seed code word also contains the
(9 bits)
SEED CODE WORD FORMAT
(1-Bit)
V
LOW
LOW
1
, CRC, and QUEUE). The
Function
1
(4 Bits)
1
1
2
.
2
.
Preliminary
• The button code for transmitting a seed code
• The seed transmissions before the counter incre-
• The limit of 127 for SDLM or SDMD can be
the serial number and the seed from a single but-
ton press.
word can be selected with the Seed Button
(SDBT) configuration option. SDBT bits 0 to 3 cor-
respond to button inputs S0 to S3. Set the bits
high for the button combination that should trigger
a seed transmission (i.e., If SDBT = 1010
S3+S1 will trigger a seed transmission).
ments past 128 can be modified with the Seed
Mode (SDMD) configuration option. Setting this
bit for Production mode will cause the selected
seed button combination to first transmit a normal
hopping code word for the selected Minimum
Code words (MTX) and then at least MTX seed
code words until all buttons are released. This
mode is disabled after the counter reaches 128
even if the 16/20-bit counter rolls over to 0.
reduced by using an initial counter value >0.
Note:
SEED Code
(60 bits)
SEED
The synchronization counter only incre-
ments on code hopping transmissions.
The counter will not advance on a seed
transmission unless Seed Delay or Pro-
duction mode options are on.
Transmission Direction LSB First
HCS370
DS41111D-page 13
2
then,