BQ4285LP datasheet(6/32 Pages) TI

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Interrupts

The bq4285E/L allows three individually selected inter-

rupt events to generate an interrupt request.

These

three interrupt events are:

The periodic interrupt, programmable to occur once

every 122

µs to 500 ms.

The alarm interrupt, programmable to occur once per

second to once per day, is active in battery-backup

mode, providing a “wake-up” feature.

The update-ended interrupt, which occurs at the end

of each update cycle.

Each of the three interrupt events is enabled by an indi-

vidual interrupt-enable bit in register B. When an event

occurs, its event flag bit in register C is set. If the corre-

sponding event enable bit is also set, then an interrupt

request is generated.

The interrupt request flag bit

(INTF) of register C is set with every interrupt request.

Reading register C clears all flag bits, including INTF,

and makes INT high-impedance.

Two methods can be used to process bq4285E/L inter-

rupt events:

Enable interrupt events and use the interrupt request

output to invoke an interrupt service routine.

Do not enable the interrupts and use a polling routine

to periodically check the status of the flag bits.

The individual interrupt sources are described in detail

in the following sections.

Periodic Interrupt

The mux output used to drive the SQW output also

drives the interrupt-generation circuitry. If the periodic

interrupt event is enabled by writinga1tothe periodic

interrupt enable bit (PIE) in register C, an interrupt re-

quest is generated once every 122

µs to 500ms. The pe-

riod between interrupts is selected by the same bits in

ble 3). Setting OSC2–OSC0 in register A to 011 does

not affect the periodic interrupt timing.

Square Wave

Periodic Interrupt

OSC2

OSC1

OSC0

RS3

RS2

RS1

RS0

Frequency

Units

Period

Units

0100000

None

0100001

256

3.90625

0100010

128

7.8125

0100011

8.192

kHz

122.070

µs

0100100

4.096

kHz

244.141

µs

0100101

2.048

kHz

488.281

µs

0100110

1.024

kHz

976.5625

µs

0100111

512

1.95315

0101000

256

3.90625

0101001

128

7.8125

0101010

15.625

0101011

31.25

0101100

62.5

0101101

125

0101110

250

0101111

500

XXXX

32.768

kHz

same as above defined

by RS3–RS0

Table 3. Square-Wave Frequency/Periodic Interrupt Rate

bq4285E/L

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