pcf2127a NXP Semiconductors, pcf2127a Datasheet - Page 44

• Manufacturer Part Number: pcf2127a
• Description: Integrated Rtc, Tcxo And Quartz Crystal
• Manufacturer: NXP Semiconductors

NXP Semiconductors
PCF2127A_1
Product data sheet
8.12.4 Dependency between Battery switch-over and timestamp
8.13 Interrupt output, INT
The timestamp function depends on the control bit BTSE in register Control_3:
Table 52.
[1]
PCF2127A has an interrupt output pin INT which is open-drain, active LOW. Interrupts
may be sourced from different places:
The control bit TI_TP (register Watchdg_tim_ctl) is used to configure whether the
interrupts generated from the second/minute timer (flag MSF in register Control_2) and
the countdown timer (flag CDTF in register Control_2) are pulsed signals or a
permanently active signal. All the other interrupt sources generate a permanently active
interrupt signal which follows the status of the corresponding flags. When the interrupt
sources are all disabled, INT remains high-impedance.
BTSE BF
0
1
•
•
•
•
•
•
•
•
•
•
Default value.
second or minute timer
countdown timer
watchdog timer
alarm
timestamp
battery switch-over
battery low detection
The flags MSF, CDTF, AF, TSFx and BF can be cleared by using the interface
The flags WDTF is read only. How it can be cleared is explained in
The flag BLF is read only. It is cleared automatically from the battery low detection
circuit when the battery is replaced
-
0
1
Battery switch-over and timestamp
[1]
Description
the battery switch-over does not affect the timestamp registers
If a battery switch-over event occurs:
the timestamp registers store the time and date when the switch-over occurs;
after this event occurred BF is set logic 1
the timestamp registers are not modified;
in this condition subsequent battery switch-over events or falling edges on pin
TS are not registered
Rev. 01 — 21 January 2010
Integrated RTC, TCXO and quartz crystal
PCF2127A
© NXP B.V. 2010. All rights reserved.
Section 8.11.6
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