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Unformatted text preview: UC Berkeley, EECS Department B. E. Boser EECS 40 HW10: Microcontroller UID: 1. A microcontroller operates at MHz and executes one operation in each cycle (e.g. fetch data from memory, addition). a) What is the time required to execute a single instruction? 1 pt. b) How much time does it take to sum up numbers stored in memory? Note that the microcontroller must load a number from memory before performing an addition and that it can keep intermediate results stored in the CPU. State your result to 5 % accuracy. 1 pt. 1 2. A microcontroller consumes I ss 1 = μ A when active and I ss 2 = 0.5 μ A in sleep mode (CPU turned off). It is programmed as a temperature logger and turns on once every minutes for s to take a measurement and then goes back to sleep. Calculate how long the circuit can be powered with a hearing aid battery with J capacity at V dd = V (assume that the entire energy from the battery can be used). 1 pt. 2 3. Light emitting diodes (LEDs) follow an exponential relationship between voltage and current: i D = I s e v D V t (1) V t = k B T q e (2) In this equation k B is Boltzmann’s constant, T is the absolute temperature in Kelvin, and q e is the electronic charge (charge of an electron). As a result of the exponential relationship, small variations of the voltage across the diode or the temperature translate into large changes of current (and LED brightness) and can result in the LED burning out. By placing a resistor in series with the diode, these problems can be avoided....
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This note was uploaded on 01/15/2011 for the course EE 40 taught by Professor Chang-hasnain during the Fall '07 term at Berkeley.
- Fall '07