hcs370 Microchip Technology Inc., hcs370 Datasheet - Page 12

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

HCS370
FIGURE 3-2:
3.2.3.1
A low battery voltage detector onboard the HCS370
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 checked on
the first preamble pulse of each code word with the
LED momentarily turned off. The V
ted in each code word so the decoder can give an indi-
cation to the user that the transmitter battery is low.
Operation of the LED changes as well to further indi-
cate 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, like a Schmitt Trigger.
This will effectively hold the V
tery is replaced. If the Low Voltage Latch is enabled,
then the low T
stretch by 4 ms one time as the latch changes state.
DS41111D-page 12
With XSER=1, 20-bit Counter, QUEN=0
With XSER=0, 20-bit Counter, QUEN=1
Q1 Q0 C1 C0
2 Bits
QUE
Status Information
Status Information
C1 C0
2 Bits
CRC
(5 Bits)
(3 Bits)
2 Bits
CRC
Low Voltage Detector Status (V
E
CODE WORD DATA FORMAT (20-BIT COUNTER)
after the first preamble pulse can
V
V
1-Bit
1-Bit
LOW
LOW
S2 S1 S0
4 Bits
BUT
LOW
bit high until the bat-
Fixed Code Portion (32 Bits)
Fixed Code Portion (32 Bits)
S3
LOW
SERIAL NUMBER
bit is transmit-
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)
8 Bits
8 Bits
DISC
DISC
Transmission Direction LSB First
2002 Microchip Technology Inc.
19
19
Synchronization
Synchronization
Counter
Counter
20 Bits
20 Bits
0
0