Maxim-integrated MAX31782 Manual do Utilizador descarregar pdf (Página 17)

Maxim Integrated 2-13

MAX31782 User’s Guide

Revision 0; 8/11

2.6.2 Watchdog Timer Reset

The watchdog timer is a programmable hardware timer that can be used to reset the processor in case a software

lockup or other unrecoverable error occurs. Once the watchdog is enabled, software must reset the watchdog timer

periodically. If the processor does not reset the watchdog timer before it elapses, the watchdog can initiate a reset.

If the watchdog resets the processor, the MAX31782 remains in reset and holds the RST pin low for 12 clock cycles.

When a reset occurs due to a watchdog timeout, the watchdog timer reset flag (WTRF) in the WDCN register is set to

indicate the source of the reset.

2.6.3 External Reset

During normal operation, the MAX31782 is placed into external reset when the RST pin is held at logic 0 for at least four

clock cycles. Once the MAX31782 enters reset mode, it remains in reset as long as the RST pin is held at logic 0. After

the RST pin returns to logic 1, the processor exits reset within 12 clock cycles.

An external reset pulse on the RST pin can also bring the MAX31782 out of its low-power stop mode. When this occurs,

the MAX31782 resets and returns to normal CPU mode operation within 10 clock cycles.

2.6.4 Internal System Resets

There are two possible sources of internal system resets. An internal reset holds the MAX31782 in reset mode for 12

clock cycles.

1) When data BBh is written to the special I

C slave address 34h.

2) When in-system programming is complete and the ROD bit is set to 1.

Figure 2-6. MAX31782 State Diagram

POR

SYSTEM CLOCK

STARTUP DELAY

SU:MOSC

PORT6 GPIO INT, I

START INT, SVM INT

OR EXT RESET

CKCN.STOP = 1

> V

< V

BROWNOUT STATE

CPU DISABLED

ANALOG ACTIVE

CPU MODE

DIGITAL CORE ON

ANALOG ON

CODE IS EXECUTING

STOP MODE

DIGITAL CORE OFF

ANALOG ON

SVM MONITOR DEPENDS

ON SVMEN AND SVMSTOP

1 2 ... 12 13 14 15 16 17 18 19 20 21 22 ... 222 223

MAX31782 User’s Guide 1

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