PCF2123BS NXP [NXP Semiconductors], PCF2123BS Datasheet - Page 17

• Manufacturer Part Number: PCF2123BS
• Description: SPI Real time clock/calendar
• Manufacturer: NXP [NXP Semiconductors]

NXP Semiconductors
PCF2123_1
Product data sheet
9.6.1 Data flow
9.7 Alarm function
Figure 11
In order to read the correct time it is important to read all time registers in one access i.e.
seconds up to years. If the time registers are read by making individual access to the chip,
then there is the risk that the time will increment between accesses.
When one or more of these registers are loaded with a valid minute, hour, day or weekday
and its corresponding alarm enable not bit (AEN_x) is logic 0, then that information will be
compared with the current minute, hour, day and weekday.
Table 18.
[1]
Bit
7
6 to 0
Fig 11. Data flow for the time function
Values shown in decimal.
Symbol
AEN_M
MINUTE_ALARM 00 to 59
shows the data flow and data dependencies starting from the 1 Hz clock tick.
Register Minute_alarm (address 09h) bits description
Rev. 01 — 19 November 2008
12_24 hour mode
CALCULATION
LEAP YEAR
Value
0
1
[1]
Description
minute alarm is enabled
minute alarm is disabled
this register holds the minute alarm information coded in
BCD format
SECONDS
MINUTES
MONTHS
1 Hz tick
HOURS
YEARS
DAYS
WEEKDAY
SPI Real time clock/calendar
001aaf901
PCF2123
© NXP B.V. 2008. All rights reserved.
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