bq3285ED/LD
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.
32kHz Output
The bq3285ED/LD provides for a 32.768kHz output, and
the output is always active whenever VCC is valid (VPFD
+ tCSR). The bq3285ED/LD output is not affected by the
bit settings in Register A. Time-keeping aspects, how-
ever, still require setting OS0-OS2.
Two methods can be used to process bq3285ED/LD in-
terrupt events:
Interrupts
The bq3285ED/LD allows three individually selected in-
terrupt events to generate an interrupt request. These
three interrupt events are:
Enable interrupt events and use the interrupt
request output to invoke an interrupt service routine.
The periodic interrupt, programmable to occur once
Do not enable the interrupts and use
a polling
every 122µs to 500ms.
routine to periodically check the status of the flag
bits.
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 individual interrupt sources are described in detail
in the following sections.
The update-ended interrupt, which occurs at the end
of each update cycle.
Table 3. Periodic Interrupt Rate
Register A Bits
Periodic Interrupt
OSC2
OSC1
OSC0
RS3
0
RS2
0
RS1
0
RS0
0
Period
None
3.90625
Units
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
ms
ms
µs
0
0
1
0
7.8125
122.070
244.141
488.281
976.5625
1.95315
3.90625
7.8125
15.625
31.25
0
0
1
1
0
1
0
0
µs
0
1
0
1
µs
0
1
1
0
µs
0
1
1
1
ms
ms
ms
ms
ms
ms
ms
ms
ms
1
0
0
0
1
0
0
1
1
0
1
0
1
0
1
1
1
1
0
0
62.5
1
1
0
1
125
1
1
1
0
250
1
1
1
1
500
same as above defined
by RS3–RS0
0
1
1
X
X
X
X
July 1997
6
TI [ TEXAS INSTRUMENTS ]
