DS1831C/D/E

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OPERATION - WATCHDOG TIMER

does not have a transition (high-to-low or low-to-high) within the predetermined time period.

The

minimum watchdog time-out would be 10 ms, TD floating would yield a minimum time-out of 100 ms,

pin prior to time-out, the watchdog timer is reset and begins to time-out again. If the watchdog timer is

output would be connected to one of the Pushbutton inputs and would not require an external pull-up

resistor. The value of the resistors is not critical in most cases but must be set low enough to pull the

output to a high state. A common value used is 10 k

input an additional pull-up resistor can be used (to improve speed of transitions) but is not required.

microprocessor address signals, data signals, or control signals. When the microprocessor functions

normally, these signals would, as a matter of routine, cause the watchdog to be reset prior to time-out. To

guarantee that the watchdog timer does not time-out, a transition must occur at or less than the minimum

times shown in Table 1. A typical circuit example is shown in Figure 10. The watchdog timing is shown

in Figure 11.

The DS1831A watchdog function cannot be disabled. The watchdog strobe input must be strobed to avoid

a watchdog time-out however the watchdog status output can be disconnected yielding the same result.

WATCHDOG CIRCUIT EXAMPLE Figure 10

R1

DS1831D

GND

WDS

IN1

NMI1

R2

ST

µP

10 k

Ω