33989 datasheet(23/66 Pages) FREESCALE

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Analog Integrated Circuit Device Data

Freescale Semiconductor

33989

FUNCTIONAL DEVICE OPERATION

RESET AND WATCHDOG PINS, SOFTWARE WATCHDOG OPERATIONS

1. Mode 1

2. Mode 2 (also called Safe mode)

These modes are independent of the SBC modes

(Normal, Standby, Sleep, and Stop). Modes 1 and 2 selection

is achieved through the SPI (register MCR, bit SAFE). Default

mode after reset is Mode 1.

Table 5 provides Reset and Watchdog output mode

of operation. Two modes (modes 1 and 2) are available and

can be selected through the SPI Safe bit. Default operation,

after reset or power-up, is Mode 1.

In both modes reset is active at device power-up and

wake-up.

• In mode 1–Reset is activated in case of VDD1 fall or

watchdog not triggered. WD output is active low as soon

as reset goes low. It remains low as long as the watchdog

is not properly re-activated by the SPI.

• In mode 2–(Safe mode) Reset is not activated in case of

watchdog fault. WD output has the same behavior as in

mode 1–The Watchdog output pin is a push-pull structure

driving external components of the application for signal

instance of an MCU wrong operation.

33989 Datasheet(PDF) 23 Page - Freescale Semiconductor, Inc