NXP Semiconductors
PCF8563
Real-time clock/calendar
8.4 Time and date registers
The majority of the registers are coded in the BCD format to simplify application use.
8.4.1 Register VL_seconds
Table 8.
Bit
7
VL_seconds - seconds and clock integrity status register (address 02h) bit
description
Value
0
1
6 to 4 SECONDS 0 to 5
3 to 0
[1]
Start-up value.
Symbol
VL
Place value Description
-
-
ten’s place
unit place
clock integrity is guaranteed
integrity of the clock information is not guaranteed
actual seconds coded in BCD format, see
0 to 9
Table 9.
Seconds coded in BCD format
Upper-digit (ten’s place)
Bit 6
0
0
0
:
0
0
:
1
1
Bit 5
0
0
0
:
0
0
:
0
0
Bit 4
0
0
0
:
0
1
:
1
1
Digit (unit place)
Bit 3
0
0
0
:
1
0
:
1
1
Bit 2
0
0
0
:
0
0
:
0
0
Bit 1
0
0
1
:
0
0
:
0
0
Bit 0
0
1
0
:
1
0
:
0
1
Seconds value
(decimal)
00
01
02
:
09
10
:
58
59
8.4.1.1
Voltage-low detector and clock monitor
The PCF8563 has an on-chip voltage-low detector (see
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.
mgr887
V
DD
normal power
operation
period of battery
operation
V
low
t
VL set
Fig 7.
Voltage-low detection
PCF8563
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© NXP B.V. 2011. All rights reserved.
Product data sheet
Rev. 9 — 16 June 2011
9 of 45
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