FinalSummer2010 - 28-07-2010 BILKENT UNIVERSITY EEE212...

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1 28-07-2010 BILKENT UNIVERSITY EEE212 Microprocessors – 2010 Summer Semester Final Open TextBook Closed Notes , Calculators Allowed Use the boxes provided for your answers! Use comments for readability , otherwise the programs will be partially graded! Duration: 2 hours and 30 minutes Q1 (20 points) Q2 (20 points) Q3 (30 points) Q4 (30 points) TOTAL SOLUTION
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2 Q-1) [20 pts] Answer the following questions: a) What happens if an Interrupt Service Routine ends with a RET, instead of RETI? Any same or lower priority interrupt that arrives later will not be served. b) Assume that External hardware interrupt 0 (in the low level triggered mode) and Timer 1 interrupts are enabled and they have low priority. What happens if a logic 0 signal arrives to the INT0 pin while Timer 1 ISR is being executed? If the signal level is still low after Timer 1 ISR is finished, then external interrupt will be served. c) Assume that External hardware interrupt 1 is enabled as edge triggered and an interrupt request arrives for that interrupt. When is the IE1 flag cleared? IE1 flag is cleared with the call to the corresponding address (13H for external interrupt 1) in the interrupt vector table. d) We want to use Counter 0 in the auto-reload mode and Timer 1 in the 16 bit timer mode. Counter 0 should be started/stopped only by software, while Timer 1 should be able to be stopped both by software and hardware. What is the corresponding value of the TMOD register for this configuration? 1001 0110 = 96H
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3 Q2-) [20 pts] The following program is supposed to perform the following task: Whenever a byte of data is received through the serial port, a LED connected to P2.0 will be turned on. Let B denote the byte received through the serial port. The LED will stay on for an amount of time equal to B x10.85 milliseconds , and then it will be turned off (You can assume no other byte will arrive through the serial port while the LED is on). If a high to low pulse arrives at pin P3.3, the LED will be immediately turned off and the character ‘N’ will be transmitted through the serial port. (You can
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FinalSummer2010 - 28-07-2010 BILKENT UNIVERSITY EEE212...

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