HCS365 datasheet(12/34 Pages) MICROCHIP

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HCS365

DS41109D-page 12

Preliminary

FIGURE 3-2:

CODE WORD DATA FORMAT (20-BIT COUNTER)

3.2.3.1

Low Voltage Detector Status (VLOW)

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 VDD voltage is raised above this level, indicating

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

VLOW bit high until the battery is replaced. If the Low

Voltage Latch is enabled, then the break after the first

preamble pulse can stretch by 4 ms one time as the

latch changes state.

Fixed Code Portion (32 Bits)

QUE

2 Bits

CRC

2 Bits

VLOW

1-Bit

SERIAL NUMBER

(28 Bits)

Q1 Q0 C1 C0

S2 S1 S0

BUT

4 Bits

DISC

8 Bits

Synchronization

20 Bits

Counter

S0 S3

Hopping Code Portion (32 Bits)

With XSER=0, 20-bit Counter, QUEN=1

Status Information

(5 Bits)

BUT

4 Bits

Fixed Code Portion (32 Bits)

CRC

2 Bits

VLOW

1-Bit

SERIAL NUMBER

(32 Bits)

C1 C0

BUT

4 Bits

DISC

8 Bits

Synchronization

20 Bits

Counter

S0 S3

Hopping Code Portion (32 Bits)

With XSER=1, 20-bit Counter, QUEN=0

Status Information

(3 Bits)

Transmission Direction LSB First

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