PCF8563 All information provided in this document is subject to legal disclaimers. © NXP Semiconductors N.V. 2015. All rights reserved.
Product data sheet Rev. 11 — 26 October 2015 10 of 45
NXP Semiconductors
PCF8563
Real-time clock/calendar
8.4.1.1 Voltage-low detector and clock monitor
The PCF8563 has an on-chip voltage-low detector (see Figure 6
). When V
DD
drops below
V
low
, bit VL in the VL_seconds register is set to indicate that the integrity of the clock
information is no longer guaranteed. The VL flag can only be cleared by using the
interface.
The VL flag is intended to detect the situation when V
DD
is decreasing slowly, for example
under battery operation. Should the oscillator stop or V
DD
reach V
low
before power is
re-asserted, then the VL flag is set. This will indicate that the time may be corrupted.
8.4.2 Register Minutes
8.4.3 Register Hours
8.4.4 Register Days
[1] The PCF8563 compensates for leap years by adding a 29th day to February if the year counter contains a
value which is exactly divisible by 4, including the year 00.
Fig 6. Voltage-low detection
VL set
normal power
operation
period of battery
operation
t
V
DD
V
low
mgr887
Table 10. Minutes - minutes register (address 03h) bit description
Bit Symbol Value Place value Description
7 - - - unused
6 to 4 MINUTES 0 to 5 ten’s place actual minutes coded in BCD format
3 to 0 0 to 9 unit place
Table 11. Hours - hours register (address 04h) bit description
Bit Symbol Value Place value Description
7 to 6 - - - unused
5 to 4 HOURS 0 to 2 ten’s place actual hours coded in BCD format
3to0 0to9 unit place
Table 12. Days - days register (address 05h) bit description
Bit Symbol Value Place value Description
7 to 6 - - - unused
5to4 DAYS
[1]
0 to 3 ten’s place actual day coded in BCD format
3to0 0to9 unit place
