Although this device uses an I2C interface with communication speeds up to 1 MHz, two of the eight pins are dedicated to Alert (pin3) and nReset (pin 6). The Alert pin is intended to be connected, if desired, to an interrupt pin on a microcontroller. According to section 3.5 (ALERT Pin) of the datasheet, "The output of the pin depends on the value of the temperature reading relative to programmable limits," and its function is "explained in a separate application note.
It’s always good to be cognizant of trace lengths when you’re laying out a parallel bus, though at moderate frequencies it is nothing to stress about. The propagation time for a signal traveling through a trace is maybe 150 picoseconds/inch. So if you have two traces with a length mismatch of one inch, one signal will arrive 150 ps after the other signal. If your signals are transitioning at a frequency whose corresponding period is much greater than 150 ps, this one-inch mismatch won’t cause problems. Even at 100 MHz (which is pretty fast for a parallel bus), the period is 10 ns, i.e., ~67 times larger than the time-of-arrival discrepancy for a one-inch mismatch.
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