pcf2129a NXP Semiconductors, pcf2129a Datasheet - Page 30

• Manufacturer Part Number: pcf2129a
• Description: Integrated Rtc, Tcxo And Quartz Crystal
• Manufacturer: NXP Semiconductors

NXP Semiconductors
PCF2129A_1
Product data sheet
8.10.3 Watchdog timer function
Table 32.
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.
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. A read of the register Control_2 will automatically reset the
flag WDTF.
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
clock frequency
4.096
64
1
1
⁄
60
Programmable watchdog timer
Rev. 01 — 13 January 2010
Table
30).
Units
kHz
Hz
Hz
Hz
Minimum timer
period (n = 1)
244
15.625
1
60
Integrated RTC, TCXO and quartz crystal
Units
μs
ms
s
s
Maximum timer
period (n = 255)
62.256
3.984
255
15300
1
⁄
60
Hz (see
PCF2129A
© NXP B.V. 2010. All rights reserved.
Table
32).
Units
ms
s
s
s
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