PCF2129AT/2,518 NXP Semiconductors, PCF2129AT/2,518 Datasheet - Page 31

• 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
8.10.3 Watchdog timer function
Table 33.
The watchdog timer function is enabled or disabled by the WD_CD bit of the register
Watchdg_tim_ctl (see
The two bits TF[1:0] in register Watchdg_tim_ctl determine one of the four source clock
frequencies for the watchdog timer: 4.096 kHz, 64 Hz, 1 Hz, or
When the watchdog timer function is enabled, the 8-bit timer in register Watchdg_tim_val
determines the watchdog timer period (see
The watchdog timer counts down from the software programmed 8-bit binary value n in
register Watchdg_tim_val. When the counter reaches 1, the watchdog timer flag WDTF
(register Control_2) is set logic 1 and an interrupt will be generated.
The counter does not automatically reload.
When WD_CD is logic 0 (watchdog timer disabled) and the microcontroller unit (MCU)
loads a watchdog timer value n, then:
Loading the counter with 0 will:
Remark: WDTF is read only and cannot be cleared by command. WDTF can be cleared
by:
Writing a logic 0 or logic 1 to WDTF has no effect.
TF[1:0] Timer source
00
01
10
11
•
•
•
•
•
•
•
•
the flag WDTF is reset
INT is cleared
the watchdog timer starts again
reset the flag WDTF
clear INT
stop the watchdog timer
loading a value in register Watchdg_tim_val
reading of the register Control_2
clock frequency
4.096
64
1
1
⁄
60
Programmable watchdog timer
All information provided in this document is subject to legal disclaimers.
Rev. 5 — 12 February 2013
Table
31).
Units
kHz
Hz
Hz
Hz
Minimum timer
period (n = 1)
244
15.625
1
60
Table
Integrated RTC, TCXO and quartz crystal
33).
Units
s
ms
s
s
Maximum timer
period (n = 255)
62.256
3.984
255
15300
1
⁄
60
PCF2129AT
Hz (see
© NXP B.V. 2013. All rights reserved.
Table
33).
Units
ms
s
s
s
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