| 摘要 |
A system for conserving battery life in a battery operated device such as a tire tag where there are several modes of operation. The typical mode is the deep sleep mode where the tag is generally inactive (no clock is running; however, an RC watchdog timer is running, which uses very little power). The tag spends most of its time in this low power mode. The tag periodically partially awakens to a lucid sleep mode (when the watchdog timer times out), initiates a low-speed clock, determines if it is time to enter a search mode by examining a search mode counter and, if it is not time, adjusts the search mode counter (e.g., decrements the counter by one), and returns to the deep sleep mode. The tag sleeps in the deep sleep mode most of its life in an effort to conserve battery power. During the deep sleep mode, because the clock oscillators are OFF, a deep sleep counter is adjusted (incremented or decremented) periodically (e.g., about every 18 ms) by an internal R/C oscillator. The internal watchdog timer (WDT) monitors the deep sleep counter and when the deep sleep counter, for example, contains a NULL value (all zeroes) the WDT wakes up the microcontroller (i.e., the WDT initiates the low-speed clock so that the tag cannot enter the lucid sleep mode). The tire tag delivers data at a slower or faster rate to achieve the important advantage of extending battery life. Also to extend battery life two oscillators are desirable because they allow two clock speeds. Having two clocks allows a designer to minimize use of the high-speed clock, thus conserving battery power.
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