PCF2129AT/2,518 NXP Semiconductors, PCF2129AT/2,518 Datasheet - Page 32

• Manufacturer Part Number: PCF2129AT/2,518
• Description: Real Time Clock
• Manufacturer: NXP Semiconductors
• Series: PCF2129r

Specifications of PCF2129AT/2,518

• Rohs: yes
• Function: Clock, Calendar, Alarm, Watchdog, Timestamp
• Rtc Bus Interface: I2C, SPI
• Date Format: Binary
• Time Format: Binary
• Supply Voltage - Max: 4.2 V
• Supply Voltage - Min: 1.2 V
• Maximum Operating Temperature: + 60 C
• Minimum Operating Temperature: - 15 C
• Mounting Style: SMD/SMT
• Package / Case: SOP-20
• Battery Backup Switching: Yes
• Factory Pack Quantity: 2000

NXP Semiconductors
PCF2129AT
Product data sheet
8.10.4 Pre-defined timers: second and minute interrupt
8.10.5 Clearing flags
PCF2129AT has two pre-defined timers which are used to generate an interrupt either
once per second or once per minute. The pulse generator for the minute or second
interrupt operates from an internal 64 Hz clock. It is independent of the watchdog timer.
Each of these timers can be enabled by the bits SI (second interrupt) and MI (minute
interrupt) in register Control_1.
The flags MSF, AF, and TSFx can be cleared by command. To prevent one flag being
overwritten while clearing another, a logic AND is performed during the write access. A
flag is cleared by writing logic 0 while a flag is not cleared by writing logic 1. Writing logic 1
will result in the flag value remaining unchanged.
Two examples are given for clearing the flags. Clearing a flag is made by a write
command:
Repeatedly rewriting these bits has no influence on the functional behavior.
Table 34.
Register
Control_2
Fig 17. WD_CD set logic 1: watchdog activates an interrupt when timed out
•
•
•
•
•
timer value
When the watchdog timer counter reaches 1, the watchdog timer flag WDTF (register
Control_2) is set logic 1
When a minute or second interrupt occurs, the minute/second flag MSF (register
Control_2) is set logic 1 (see
Bits labeled with - must be written with their previous values
Bits labeled with T have to be written with logic 0
WDTF is read only and has to be written with logic 0
watchdog
WDTF
INT
Counter reached 1, WDTF is logic 1, and an interrupt is generated.
Flag location in register Control_2
All information provided in this document is subject to legal disclaimers.
Bit
7
MSF
Rev. 5 — 12 February 2013
n = 1
6
WDTF
Section
5
TSF2
8.12.1).
4
AF
Integrated RTC, TCXO and quartz crystal
3
T
2
-
PCF2129AT
© NXP B.V. 2013. All rights reserved.
1
-
MCU
n
001aag062
0
T
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