IMASK FIO_FLAG_S FIO_DIR SIC_IMASK FIO_EDGE FIO_POLAR ILAT FIO_BOTH TCOUNT FIO_FLAG_D FIO_ENEN PF_STATUS_D

Transcription

1 SECTION B -- ATTEMPT NO MORE THAN 2 QUESTIONS These are open-ended questions and you may be required to make some educated, engineering relevant, design decisions. Only the first two answers to questions will be marked. Any other answers will remain unmarked. Q6A) The designer did not like the WaitForIntrude( ) way (see Q5) of waiting for an intruder. Instead the designer decides that working with PF interrupts would be a better solution. The designer develops a function void InitializePF_Registers(void) so that lines PF0, PF1, PF2 and PF3 are outputs, and lines PF4, PF5, PF6 and PF7 are inputs. This interface is needed for an intruder-location indicator (see figure 1). For the first interrupt prototype test, the designer also uses the routine InitializePF_Registers( ) to configure all the necessary registers so that interrupts are to occur when lines PF4 and PF5 go from low_to_high, and interrupts occur when lines PF6 and PF7 go from high_to_low, but not for other signal transitions. A separate function InitializeTimerRegisters(void) is used to initialize the timer registers to cause interrupts every 0x2000 processor cycles In the table below, show the values that must be placed into the registers during the function InitializePF_Registers( ) for the first interrupt prototype test. To discourage guessing, marks are given for correct answers and deducted for incorrect answers. No marks will be deducted for any answer left blank. 5 marks IMASK FIO_FLAG_S FIO_DIR SIC_IMASK FIO_EDGE FIO_POLAR ILAT FIO_BOTH TCOUNT TPERIOD TSCALE FIO_MASKA_D FIO_FLAG_D FIO_ENEN PF_STATUS_D Q6B) For this question, the Blackfin PF interface has been re-configured so that interrupts will occur when line PF5 goes from low-to-high. There may be signals present on other PF lines that must not be changed (destroyed). Design, write and document an efficient C++ Blackfin assembly code interrupt service routine that increments an unsigned char variable phredda each time that a PF5 interrupt occurs. THIS VARIABLE CAN T BE DEFINED AS.EXTERN. Design the interrupt service routine so that after the 10 th interrupt, the Blackfin PF interface is changed so that interrupts will now occur when ever line PF5 goes from high-to-low. 5 marks THERE ARE TEN MARKS AVAILABLE ON THIS PAGE PAGE 8 OF 12

2 Q7 In the lectures we have discussed the relative advantages / disadvantages of using the special DMA data transfer modes for moving data between the SDRAM memory (2M) on the Blackfin evaluation board and the L1 memory internal to the Blackfin processor. We have also discussed the fact that it is possible to have several external memory blocks (256 M or greater) that are connected to the Blackfin over the SPI interface. The SPI transfer technique used in Lab. 5 with the LCD screen was rather inefficient, because the LCD screen was slow. You can, in fact, combine DMA with SPI for higher speed memory transfers. A) Explain the general concepts (advantages / disadvantages) behind DMA data transfer and SPI interfaces. Do not repeat the information you provided for Q2 in Section A. 6 marks B) Provide a reasoned argument about whether DMA transfer to SDRAM memory will be faster / slower than DMA transfer to SPI memory. Calculate how much faster / slower the transfers will be. Since we have not discussed these exact concepts in class, I am willing to accept a reasoned argument that accurately discusses the important issues and concerns that need to be considered to provide a time estimate, as well as an argument that precisely answers the question. 4 marks THERE ARE TEN MARKS AVAILABLE ON THIS PAGE PAGE 9 OF 12

3 Q8 This question is essentially equivalent to Q4, except that now you may assume that you have access to a Blackfin processor with a Motorola 68K style of assembly language. All the internal registers of the processor (FIO_DATA_D etc) have the same names and behaviour. The only thing that has changed is the assembly syntax e.g. You can t do R0 = R1; any more but instead must write MOVE.L D1, D0; Traffic speed can be measured in a simple way. You place a sensor across the road lanes it is that black line you often see stretched across the road. As the front tire of the car goes across the sensor, a signal (low-to-high-to-low) is generated. A second signal is generated when the rear tire goes across the sensor (low-to-high-to-low). Write a C++ compatible Motorola (Diab-Data compiler) assembly language function unsigned long int TimeTaken() that returns the number of Blackfin cycles between the two traffic sensor signals. 10 marks o Assume that the PF interface has already been configured so that line PF8 is ready for an input signal. o Assume that the road sensor has been attached to line PF8 o Assume that the timer TCOUNT register contains 0xFFFFFFFF, the timer TSCALE register contains 0x2 and the timer TPERIOD register contains 0xFFFFFFFF (sufficient for 90 seconds of counting) THERE ARE TEN MARKS AVAILABLE ON THIS PAGE PAGE 10 OF 12

4 Q9) -- Don t you just hate it when you have done research beyond the course content because that area interested you you have heavily reviewed one area you thought the instructor kept on deliberately emphasizing and then the examiner does not ask any questions in that area! As promised, here is a chance to overcome that problem and show your true knowledge of interfacing and embedded systems. Make up a question related to this course AND answer it. (10 marks) TO RECEIVE FULL MARKS the question should satisfy the following criteria Be at a difficulty level appropriate for a final exam question in the 3rd year of an Electrical and Computer Engineering program. Quick test -- Would it be suitable for next year s final? The question should NOT be equivalent to any exam question already asked in this course or the current exam. Questions and answers that are a simple regurgitation of a concept handled in class will receive a D grade ( marks or less). Questions and answers that give a new insight into a concept handled in class will receive a C or a B grade (5.5 7 marks). Questions that, under different circumstances, would present A CHALLENGE FOR YOU to answer in either Section A or Section B of a final exam will receive B or A grade (7 and up), if answered correctly. A good mark on this question would be 7.5 or 8.5 marks out of 10 (B+ / A-) Most questions involving a lot of code translation will be considered similar to questions Q2 to Q8, and therefore will not receive many marks. Students who have spend time ahead of the exam planning questions that lead to answers that are clear and concise are more likely to receive higher marks. This means no long-winded answers that look like they have been thought up on the spur of the moment. Please bring the questions and answers into the exam in your head as no additional materials are allowed in this exam! Marking exams is normally as much fun as watching paint dry. Questions that entertain and give the impression that s clever and well thought out or leave the instructor wanting to boast to other instructors about what you suggested -- are more likely to receive higher marks. PAGE 11 OF 12

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6 AA BB CC DD NAME A B C D E F WW XX YY ZZ ID # When the intruder steps on button 7, the two wires make contact, making a connection between lines BB and ZZ PF0 PF1 PF2 PF3 PF4 PF5 PF6 PF7 Figure 1 needed for questions Q5 and Q6 Don t forget to add your name, and include this sheet inside your exam booklet if you want it marked.