PCA2125_1 © NXP B.V. 2008. All rights reserved.
Product data sheet Rev. 01 — 28 July 2008 10 of 36
NXP Semiconductors
PCA2125
SPI Real-time clock/calendar
Figure 6 shows the data flow and data dependencies starting from the 1 Hz clock tick.
8.5 Alarm function
When one or several alarm registers are loaded with a valid minute, hour, day or weekday
value and its corresponding alarm enable not bit (AENx) is logic 0, then that information is
compared with the current minute, hour, day and weekday value.
October X X X 1 0 0 0 0
November X X X 1 0 0 0 1
December X X X 1 0 0 1 0
Table 17. Register Years (address 08h) bit description
Bit Symbol Value Description
7 to 0 YEARS[7:0] 00 to 99 this register holds the current year value coded in BCD
format
Fig 6. Data flow for the time function
Table 16. Month assignments
…continued
Month Double-digit Digit
Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
001aaf901
1 Hz tick
12_24 hour mode
WEEKDAY
SECONDS
MINUTES
HOURS
DAYS
LEAP YEAR
CALCULATION
MONTHS
YEARS
Table 18. Register Minute_alarm (address 09h) bit description
Bit Symbol Value Description
7 AEN_M 0 minute alarm is enabled
1 minute alarm is disabled
6 to 0 MINUTE_ALARM[6:0] 00 to 59 this register holds the minute alarm value coded in
BCD format
