PCF8564A datasheet(38/86 Pages) NXP

38 / 86 page

NXP Semiconductors

PCA2131

Nano-power highly accurate RTC with integrated quartz crystal for automotive applications

Bits labeled as X are undefined at power-on and unchanged by subsequent resets.

Bit

Symbol

Value

Description

7 to 0

WATCHDG_TIM_

VAL[7:0]

00 to FF

timer period in seconds:

where n is the timer value (n > 1)

Write Only

Table 58. Watchdg_tim_val - watchdog timer value register (address 36h) bit description

TF[1:0] Timer source

clock frequency

Units

Minimum timer

period (n = 2)

Units

Maximum timer

period (n = 255)

Units

15.625

3.984

250

63.744

1⁄4

1020

1⁄64

16320

Table 59. Programmable watchdog timer

7.11.3 Watchdog timer function

The watchdog timer interrupt function is enabled or disabled by the WD_CD bit of the

The 2 bits TF[1:0] in register Watchdg_tim_ctl determine one of the four source clock

frequencies for the watchdog timer: 64 Hz, 4 Hz, 1⁄4 Hz or 1⁄64 Hz (see Table 59).

When the watchdog timer function is enabled, the 8-bit timer in register Watchdg_tim_val

determines the watchdog timer period (see Table 59).

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

(register Control_2) is set logic 1 and an interrupt is generated. The period accuracy

corresponds to n +/- 0.5.

The register Watchdg_tim_val is write only and not readable after set.

The counter does not automatically reload.

When WD_CD is logic 1/0 (watchdog timer interrupt enabled/disabled) and the Micro-

controller Unit (MCU) loads a watchdog timer value n:

• the flag WDTF is reset

• INTA/B is cleared

• the watchdog timer starts again

Loading the counter with 0 or 1 will:

• reset the flag WDTF

• clear INTA/B

• stop the watchdog timer

Remark: WDTF can be cleared by:

• loading a value in register Watchdg_tim_val

• writing a logic 0 to WDTF

PCA2131

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

Product data sheet

Rev. 1.0 — 26 July 2021

38 / 86

PCF8564A 数据表(PDF) 38 Page - NXP Semiconductors

PCF8564A 数据表(HTML) 38 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

数据表下载

链接网址

PCF8564A 数据表(PDF) 38 Page - NXP Semiconductors

PCF8564A 数据表(HTML) 38 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

数据表 下载

链接网址

数据表下载