PCF2123U/10AA/1 Просмотр технического описания (PDF) - NXP Semiconductors.
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PCF2123U/10AA/1 Datasheet PDF : 64 Pages
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NXP Semiconductors
PCF2123
SPI Real time clock/calendar
8.4 Time and date function
The majority of the registers are coded in the Binary Coded Decimal (BCD) format. BCD is
used to simplify application use. An example is shown for the seconds in Table 10.
8.4.1 Register Seconds
Table 9. Seconds - seconds register (address 02h) bit description
Bit
Symbol
Value
Place value Description
7
OS
0
-
clock integrity is guaranteed
1[1]
-
clock integrity is not guaranteed;
oscillator has stopped or has
been interrupted
6 to 4 SECONDS
3 to 0
0 to 5
0 to 9
ten’s place actual seconds coded in BCD
unit place format, see Table 10
[1] Default value.
Table 10. Seconds coded in BCD format
Seconds value Upper-digit (ten’s place)
(decimal)
Bit 7 Bit 6 Bit 5
00
0
0
0
01
0
0
0
02
0
0
0
:
:
:
:
09
0
0
0
10
0
0
0
:
:
:
:
58
0
1
0
59
0
1
0
Bit 4
0
0
0
:
0
1
:
1
1
Digit (unit place)
Bit 3 Bit 2 Bit 1
0
0
0
0
0
0
0
0
1
:
:
:
1
0
0
0
0
0
:
:
:
1
0
0
1
0
0
Bit 0
0
1
0
:
1
0
:
0
1
8.4.1.1 OS flag
The PCF2123 includes a flag (OS in register Seconds, see Table 9) which is set whenever
the oscillator is stopped (see Figure 8 and Figure 9). The flag will remain set until cleared
by software. If the flag cannot be cleared, then the PCF2123 oscillator is not running. This
method can be used to monitor the oscillator and to determine if the supply voltage has
reduced to the point where oscillation fails.
VDD
battery operation
main supply
VOSC(MIN)
PCF2123
Product data sheet
Fig 8. OS set by failing VDD
All information provided in this document is subject to legal disclaimers.
Rev. 6 — 15 July 2013
t
001aai561
© NXP B.V. 2013. All rights reserved.
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