hcs365 Microchip Technology Inc., hcs365 Datasheet - Page 12

• Manufacturer Part Number: hcs365
• Description: Keeloq Code Hopping Encoder
• Manufacturer: Microchip Technology Inc.

HCS365
FIGURE 3-2:
3.2.3.1
A low battery voltage detector onboard the HCS365
can indicate when the operating voltage drops below a
predetermined value. There are two options available
depending on the Low Voltage Trip Point Select
(VLOWSEL) configuration option. The two options pro-
vided are:
• A 2.2V nominal level for 3V operation
• A 3.2V nominal level for 5V operation
The output of the low voltage detector is transmitted in
each code word, so the decoder can give an indication
to the user that the transmitter battery is low. Operation
of the LED changes as well to further indicate that the
battery is low and needs replacing.
The output of the Low Voltage Detector can also be
latched once it has dropped below the selected value.
The Low Voltage Latch (VLOWL) configuration option
enables this option. If this option is enabled, the detec-
tor level is raised to 3V or 5V once a low battery voltage
has been detected. The original value is reinstated if
the V
that a new battery has been installed.
The Low Voltage Latch (VLOWL) if enabled works sim-
ilar to a Schmitt Trigger. This will effectively hold the
V
Voltage Latch is enabled, then the break after the first
preamble pulse can stretch by 4 ms one time as the
latch changes state.
DS41109D-page 12
LOW
With XSER=1, 20-bit Counter, QUEN=0
With XSER=0, 20-bit Counter, QUEN=1
Q1 Q0 C1 C0
2 Bits
QUE
DD
bit high until the battery is replaced. If the Low
Status Information
Status Information
C1 C0
2 Bits
voltage is raised above this level, indicating
CRC
(3 Bits)
(5 Bits)
2 Bits
CRC
Low Voltage Detector Status (V
CODE WORD DATA FORMAT (20-BIT COUNTER)
V
V
1-Bit
1-Bit
LOW
LOW
S2 S1 S0
4 Bits
BUT
Fixed Code Portion (32 Bits)
Fixed Code Portion (32 Bits)
S3
SERIAL NUMBER
SERIAL NUMBER
(32 Bits)
(28 Bits)
LOW
Preliminary
)
S2
S2
S1
S1
4 Bits
4 Bits
BUT
BUT
S0 S3
S0 S3
Hopping Code Portion (32 Bits)
Hopping Code Portion (32 Bits)
Transmission Direction LSB First
8 Bits
8 Bits
DISC
DISC
2002 Microchip Technology Inc.
19
19
Synchronization
Synchronization
Counter
Counter
20 Bits
20 Bits
0
0