PCF2127AT datasheet(45/100 Pages) PHILIPS

45 / 100 page

PCF2127

All information provided in this document is subject to legal disclaimers.

Product data sheet

Rev. 8 — 19 December 2014

45 of 100

NXP Semiconductors

PCF2127

Accurate RTC with integrated quartz crystal for industrial applications

If a new value of n is written before the end of the actual timer period, this value takes

immediate effect. It is not recommended to change n without first disabling the counter by

setting WD_CD[1:0] = 00. The update of n is asynchronous to the timer clock. Therefore

changing it on the fly could result in a corrupted value loaded into the countdown counter.

This can result in an undetermined countdown period for the first period. The countdown

value n will, however, be correctly stored and correctly loaded on subsequent timer

periods.

If this mode is enabled and the countdown timer flag CDTF is set, an interrupt signal on

INT will be generated. See Section 8.13.2 for details on how the interrupt can be

controlled.

When starting the countdown timer for the first time, only the first period will not have a

fixed duration. The amount of inaccuracy for the first timer period depends on the chosen

source clock, see Table 60.

At the end of every countdown, the timer sets the countdown timer flag (CDTF). CDTF

may only be cleared by command. The asserted CDTF can be used to generate an

interrupt (INT). The interrupt may be generated as a pulsed signal every countdown

period or as a permanently active signal which follows the condition of CDTF. TI_TP is

used to control this mode selection. The interrupt output may be disabled with the CDTIE

bit, see Table 9.

In this example, it is assumed that the countdown timer flag (CDTF) is cleared before the next

countdown period expires and that INT is set to pulsed mode.

Fig 25. General countdown timer behavior

Table 60.

First period delay for timer counter

Timer source clock

Minimum timer period

Maximum timer period

4.096 kHz

n + 1

64 Hz

n + 1

1 Hz

 1) + 1⁄

64 Hz

n + 1⁄64 Hz

1⁄60 Hz

 1) + 1⁄

64 Hz

n + 1⁄64 Hz

PCF2127AT Datasheet(PDF) 45 Page - NXP Semiconductors

PCF2127AT Datasheet(HTML) 45 Page - NXP Semiconductors

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100

Datasheet Download

Link URL