MPF0900AMBA2ES datasheet(149/205 Pages) NXP

149 / 205 page

NXP Semiconductors

PF09

Nine-channel power management IC with advanced system safety monitoring

aaa-056573

x7 + x4 + x3 + x2 + 1

Default seed = 1010 0101

Figure 39. Dynamic watchdog polynomial

When operating in dynamic WD mode, WD_SEED = 0x00 or WD_SEED = 0xFF are invalid values. The PMIC

will ignore the command and generate a WD_ERROR_I interrupt to notify the system that no action has been

taken.

14.4.3 Servicing the watchdog timer

The procedure to clear the watchdog counter is the same for both static and dynamic watchdog, with the only

difference that the seed required to clear the watchdog will keep changing when the dynamic WD mode is

enabled, whereas the seed remains stable in the static WD mode.

To service the watchdog, the MCU must write a valid response in the WD_CLEAR[7:0] bits before the watchdog

timer expires.

A valid response must meet the following conditions:

• The response is calculated as the bitwise NOT of the WD_SEED[7:0] bits.

• The response must be provided within an open window.

Providing a valid key into the WD_CLEAR[7:0] register will generate a WD_OK event.

When the MCU fails to clear the system watchdog (invalid response or WD duration expired), the device will

generate a WD_NOK event, set the WD_ERROR_I flag, and the INTB will be asserted, as long as the interrupt

is not masked

The watchdog timer will be reset after either a WD_OK or a WD_NOK event, to start a new service window.

The WD_DURATION[3:0] bits are used to set the duration of the watchdog timer to service the watchdog. The

WD timer will expire when it reaches the value set on the WD_DURATION[3:0] while WD refresh is present.

WD_DURATION[3:0]

Watchdog timer duration

0000

1 ms

0001

2 ms

0010

4 ms

0011

8 ms

0100

16 ms

0101

32 ms

0110

64 ms

0111

128 ms

1000

256 ms

1001

512 ms

1010

1024 ms

Table 196. System watchdog timer configuration bits

PF09

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

Product data sheet

Rev. 1.3 — 16 December 2025

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