PCF2127TSLASH2Y datasheet(44/100 Pages) PHILIPS

tên linh kiện	PCF2127T/2Y

Giải thích chi tiết về linh kiện	Accurate RTC with integrated quartz crystal for industrial applications

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PCF2127

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Product data sheet

Rev. 8 — 19 December 2014

44 of 100

NXP Semiconductors

PCF2127

Accurate RTC with integrated quartz crystal for industrial applications

8.11.4 Countdown timer function

The countdown timer function is controlled by the WD_CD[1:0] bits in register

Watchdg_tim_ctl (see Table 55).

The timer counts down from the software programmed 8-bit binary value n in register

Watchdg_tim_val. When the counter reaches 1

• the countdown timer flag CDTF is set

• the counter automatically reloads

• and the next time period starts

Loading the counter with 0 effectively stops the timer.

Reading the timer returns the actual value of the countdown counter.

Counter reached 1, WDTF is set logic 1, reset pulse on the RST pin is generated for a time equal

to tw(rst).

Fig 24. WD_CD[1:0] = 11: watchdog activates a reset pulse when timed out

Table 59.

Specification of tw(rst)

WD_CD[1:0]

TF[1:0]

tw(rst)

244

s

15.625 ms

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