Datasheet
PCF8523 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2013. All rights reserved.
Product data sheet Rev. 6 — 17 September 2013 19 of 78
NXP Semiconductors
PCF8523
Real-Time Clock (RTC) and calendar
An unreliable battery does not ensure data integrity during periods of backup battery
operation.
When V
BAT
drops below the threshold value V
th(bat)low
, the following sequence occurs (see
Figure 11
):
1. The battery low flag BLF is set logic 1
2. An interrupt is generated if the control bit BLIE (register Control_3) is enabled. The
interrupt remains active until the battery is replaced (BLF set logic 0) or when bit BLIE
is disabled (BLIE set logic 0)
3. The flag BLF (register Control_3) remains logic 1 until the battery is replaced. BLF
cannot be cleared using the interface. It is cleared automatically by the battery low
detection circuit when the battery is replaced
8.6 Time and date registers
Most of these registers are coded in the Binary Coded Decimal (BCD) format. BCD is
used to simplify application use. An example is shown for the array SECONDS in
Table 13
.
Fig 11. Battery low detection behavior with bit BLIE set logic 1 (enabled)
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