NO CALCULATORS ARE ALLOWED IN THIS EXAM

Transcription

1 Department of Electrical and Computer Engineering, University of Calgary ENCM415 DECEMBER 18 th, HOURS NAME:- ID#:- PLEASE WRITE CLEARLY. USE AN HB GRADE OR SOFTER (DARKER) PENCIL! WHAT I CAN=T READ WILL MARKED WRONG. CLOSED BOOK EXAM DO NOT BRING ANY UNAUTHORIZED MATERIAL INTO THE EXAM ROOM The student is provided with a copy of the reference sheet, PI/T and SDS reference sheets as part of the exam handout. NO CALCULATORS ARE ALLOWED IN THIS EXAM Attempt all THREE questions from SECTION A and ANY TWO questions from SECTION B. All questions are approximated weighted equally in terms of marks, but not difficulty On the attached Performance Analysis sheet, estimate your performance on each question for bonus marks. Maximum bonus of 5 marks The attached Performance Analysis sheet shows the topics covered in each question. Use this information to plan which questions you should answer to maximize your mark during this exam. A hint of the time to spend on each part of a question is given by the relative number of marks associated with that question part. Answer the questions in the space provided on the exam sheet. The space and marks allocated are an indication of the depth of the answer expected. Make sure that you provide appropriate documentation of code and answers as marks are allocated for this documentation. Follow standard AC/C++@ conventions and recommended safe practices in your coding. Many of the concepts in this course are subjective meaning that there may be more than one valid answer. Make sure that you support your answer. If the question says which instruction is better MOVEQ.L or MOVE.L in this situation, then answering MOVEQ will give you no marks, even if true. Support why that answer is true, preferably with examples in point form As an engineer at work, you will be expected to answer questions by coming quickly to the point. The same is true in this exam. Many students spend an unnecessary amount of time writing an extremely lengthy answer when a short answer, preferable in point form, is what is required. If the question says Provide a short answer in no more than lines then follow the instructions! Think about the answer rather than using a shot-gun approach and just writing down EVERYTHING you know. PAGE 1 OF 15

2 FIG. 1 Assume that the register and memory values of a Motorola microprocessor have been configured to appear as shown in FIG 1 just as control is transferred to the subroutine starting at location 0x5000. (Alternatively the registers and memory look like this before instruction 0x5000 is executed) The following values are in the data registers D0 = 0x4500, D1 = 0x415, D2 = 0x5028 Q1. A) I wish to set a break point to cause the simulation to break at instruction MOVE.L (A0)+, D1. Make an X on the screen picture at the location where you must click to cause that breakpoint to be set. 1 mark Q1. B) The code sequence starting at location 0x5000 is now run. CarefuLLy determine the address and data bus activity during the execution of the instruction MOVE.L D2, (A7). Use CISCsim model 5 marks FETCH PHASE ADDRESS BUS DATA BUS DECODE PHASE EXECUTE PHASE WRITE PHASE Q1. C) With the simulation stopped at the breakpoint you set at the MOVE.L (A0)+, D1 instruction, what will be the value stored in the following registers D0 register 1 mark D2 register 1 mark Z-Flag in the status register. Explain how you calculated this value 2 marks THERE ARE 10 MARKS AVAILABLE ON THIS PAGE YOUR MARK ESTIMATE / 10 PAGE 2 OF 15

3 Fig. 1 Assume that the register and memory values of a Motorola microprocessor have been configured to appear as shown in FIG 1 above just as control is transferred to the subroutine starting at location 0x5000 (repeated from the previous page.) This means that this picture is valid when the subroutine is stopped at the first breakpoint (ADDA.L #4, SP). The following values are in the data registers D0 = 0x4500, D1 = 0x415, D2 = 0x5028 Q1. D) During the execution of which instruction in the code in Fig. 1, the value 0xD081 will appear on the processor s address bus during the FETCH phase of an instruction. Circle this instruction and label with a D on the screen picture. 1 mark Q1. E) When this subroutine has been called from another part of the program and stops at the first break point (ADDA.L #4, SP), a programmer familiar with debugging practices can determine the return address that should be used when this subroutine exits. How can the programmer determine this return address, and what will be the value of this return address? 3 marks Q1. F) Explain the difference between A DEFECT and AN ERROR when programming a subroutine. 2 marks Q1. G) Which typically takes longer to fix A DEFECT or AN ERROR? Why is this true? 2 marks Q1. H) There is a very nasty defect in the subroutine above. What is that defect and why DOES IT NOT cause the subroutine to malfunction? 2 marks THERE ARE 10 MARKS AVAILABLE ON THIS PAGE YOUR MARK ESTIMATE / 10 PAGE 3 OF 15

4 Q2 A) Three students have worked very late on an ENCM415 laboratory, but are now ready to come home. However it is very cold and one of the students must go out and warm up the car for the others. To decide who goes out to start the car, they write a program. The first student writes the function void main(void), placed in file main.s. The C -code design comments have been placed down the right side of the page. Translate this design into a documented 68K assembly language program following the coding standards established for this course. 10 marks // Random number generator prototype long int Random(long int value); // Prototype for a function to select a student based on // a random number // long int WhichPerson(long int value); // Prototype for a function to print out the student number // void PrintStudent(char *pt, long int value); // void main(void) { // long int person = 0; // long int number; // long int seed = 2500; // while (person = = 0) { // number = Random(seed); // person = WhichPerson(number); // } // PrintStudent( %d\n, person); // } THERE ARE 10 MARKS AVAILABLE ON THIS PAGE YOUR MARK ESTIMATE / 10 PAGE 4 OF 15

5 Q2 continued. The other students write two versions of the function long int WhichPerson(long int value) stored in files Version1.s and Version2.s. One version of the function is written using a switch statement. The other is written to impress and uses the Dr. Smith favourite the fast lookup table. The C -code design comments have been placed down the right side of the page. Translate these designs into documented 68K assembly language subroutines following the coding standards established for this course. Q2B Function stored in file Version1.s 5 Marks // long int WhichPerson( long int value) { // long int person; // value = value & 0x07; // switch (value) { // case 7: person = 1; break; // case 6: person = 2; break; // case 5: person = 3; break; // default: person = 0; // } // return (person); // } Q2C Function stored in file Version2.s 5 Marks // static long int choice[ ] = {0, 0, 0, 0, 0, 3, 2, 1}; // long int WhichPerson( long int value) { // long int person; // value = value & 0x07; // person = choice[value]; // return (person); // } THERE ARE 10 MARKS AVAILABLE ON THIS PAGE YOUR MARK ESTIMATE / 10 PAGE 5 OF 15

6 Q3.A) It is possible to set up the PI/T for either non-latched input or for double-buffered input. Explain the difference between these terms and the consequences of using the different types of input. 2 marks Q3. B) Write the Assembly subroutine void SetUpPIT(void) that will have the following functionality. PIT2 Port A is set up for double buffered input PIT2 Port B is set up for double buffered output H4 interrupt is activated for interrupts when it goes from high to low This interrupt is a level 4 interrupt which will call the C ISR Routine _DoThisNow( ) Set up the vector table to handle the H4 interrupt. Saves the old status register and enables the processor to recognize level 4 interrupts You have been provided with the manufacturer s data table for the PI/T device as part of the exam documentation. 8 marks RTS THERE ARE 10 MARKS AVAILABLE ON THIS PAGE YOUR MARK ESTIMATE / 10 PAGE 6 OF 15

7 Q3.C) Consider the ISR code sequence given in the picture above. Complete the table below to show the processor bus activity during the execution of the instruction starting at location 0x1048. Label the instruction phases. Mark unknown if no known changes are occurring on the bus (e.g. during the EXECUTE PHASE) 1 mark PHASE ADDRESS BUS DATA BUS Q3 D) Show the timing relationship between the valid/invalid address bus values, valid/invalid data bus values, the Address Strobe AS*, the Data Strobe DS* and the cycle clock phases (S0 to S7) during the FETCH phase of the instruction starting at location 0x marks ADDRESS BUS DATA BUS ADDRESS STROBE (AS*) DATA STROBE (DS*) S1 S3 S5 S7 S0 S2 S4 S6 S0 NOTE THE RELATIONSHIP BETWEEN THE SIGNALS OF YOUR TIMING DIAGRAM COUNTS Q3.E) Consider the instruction MOVE.L 0x5000.L, 0x4000.L in the ISR code sequence given in the picture above. Complete the table below to detail the number of memory read and write operations that are occurring during each phase of the instruction. 3 marks PHASE FETCH DECODE EXECUTE WRITEBACK READ NONE OPERATIONS WRITE OPERATIONS Q3. F) Basing your answer on the information given in the picture at the top of this page, provide the hexadecimal codes that would be stored in memory to form the following instructions. MOVEQ.L #6, D1 1 mark MOVE.L #0x , 0x415.L 1 mark THERE ARE 10 MARKS AVAILABLE ON THIS PAGE YOUR MARK ESTIMATE / 10 PAGE 7 OF 15

8 SECTION B ATTEMPT ANY 2 QUESTIONS FROM THIS SECTION THE QUESTIONS IN THIS SECTION ARE INTENDED TO BE MORE DIFFICULT THAN THOSE FROM SECTION A These are open-ended questions and you may be required to make some educated, engineering relevant, design decisions. Since these are open-ended questions then make sure that you don t spend an unreasonable amount of time answering the questions. Q4 A) How many bits can be carried on the data bus at the same time? How many write operations are needed to store a LONG value to the data memory 2 marks Q4B) The instruction MOVE.B 0x500.W, 0x L is a perfectly valid, if unusual instruction. What does this instruction do, and how come it involves all three types of extensions.b,.w and.l? 4 marks Q4C) Translate the following C code segment into a valid assembly language segment following the coding conventions established for this course. Determine the integer value stored in variable C. Integer stored in variable C is static char A = 39; static char B = 120; static char C; C = A + B; 4 marks THERE ARE 10 MARKS AVAILABLE ON THIS PAGE YOUR MARK ESTIMATE / 10 PAGE 8 OF 15

9 Q4D) A key element in writing interrupt service routines is code speed. You want to spend as little time in the ISR routine as possible. Consider the basic for-loop constructs used in the example below Example_ISR: LOOP: ENDLOOP: SUB.L #16, SP MOVEM.L D0-D1/A0-A1, (SP) START TIMING HERE MOVE.L #0, D0 CMP.L #1000, D0 BGE END_LOOP JSR SomeCode // Assume this subroutine (including JSR) executes in 200 clock ticks ADD.L #1, D0 JMP LOOP FINISH TIMING HERE MOVEM.L (SP), D0-D1/A0-A1 ADD.L #16, SP RTE How long will it take (in clock ticks) for the code between the two timing markers to execute? You will need to show your calculations to receive full marks for this question. Remember no calculators are allowed in this exam. 4 marks Changing the style in which the code is written could speed up the operation of the for-loop. Describe and demonstrate several coding practices that could be used to speed up this code. After rewriting the code using the techniques you describe, what percentage increase has been achieved in the speed of this ISR routine? 6 marks THERE ARE 10 MARKS AVAILABLE ON THIS PAGE YOUR MARK ESTIMATE / 10 PAGE 9 of 15

10 Q5) As I said in lectures, the Analog Devices TMP04 is a simple, neat digital thermometer chip that I plan to use in 2002 Lab 2 for ENCM415. As can be seen from the picture below, the TMP04 has just three pins, V+ (which needs 5V and only 1.3mA), GND (needs 0V) and the output signal Dout. With the device powered up (V+ and GND connected to a power source), the Dout signal is a serial stream of bits that represents the digital temperature of the device. The bit patterns in the digital stream will change with the temperature as you warm up, or cool down, the device and. By counting the high-to-low transitions of the bit stream signal, we can build a temperature sensitive clock whose signal pulses change in frequency as a function of temperature. In this question we are going to review basic ideas about bit streams. Then we are going to hook up the TMP04 to the PI/T from Lab. 2 and write the code necessary to produce the temperature sensitive clock. BACKGROUND INFORMATION The hexadecimal temperature 0x60 is represented by the bit pattern % When a hexadecimal temperature is transmitted over a serial line, its bit pattern is transmitted with a starting 1 (start bit) and two trailing 1 s (stop bits). Thus the temperature 0x64 = % is transmitted as the signal % If the stream of bits from the TMP04 device is read via a PI/T pin, the stream of bits will look like 2 clock pulses one clock pulse formed from the transition in bits 10, another clock pulse from the transition in the bits The final bits 11 will join up with the start bit 1 of the next serial stream so the bits will not form a third clock pulse Q5A) What is the bit pattern associated with the higher hexadecimal temperature 0xAA? How will the bit pattern from the higher temperature 0xAA be transmitted over the serial line? How many clock pulses are formed by the serial stream of bits that represent the temperature 0xAA? 3 marks Q5 B) The schematic below shows the Laboratory PI/T interface, a 20 khz clock pulse generator together with the TMP04 device. Pin A7 is to be hooked to V+ to provide power. Pin A0 is to be hooked up to GND. Pin A1 is to be hooked up to the Dout signal. Pin A5 is to be hooked up to the pulse generator. Pin A3 is an output clock signal that will be generated by software. Show how the devices should be connected to perform the task described above. Use arrows on the connection lines to indicate whether the PI/T pins are hooked up for use as input or output signal. Mark unconnected pins by a line terminating with an X (don t care) 2 marks LSB * * * * PI/2 * PORTA * * MSB * 20 khz Pulse Generator V+ Analog GND Devices D out TP04 H2 * Q5C) Develop, document and completely code a documented 68K assembly language subroutine void ResetDevice(void) that has the following functionality Configures the PI/T for non-latched input, single buffered output on the appropriate pins to handle the task described above Provides the necessary signals to power up the TMP04 device and make it start working providing a serial stream whose high-to-low transitions will occur at a rate that changes as the device temperature changes 5 marks THERE ARE 10 MARKS AVAILABLE ON THIS PAGE YOUR MARK ESTIMATE / 10 PAGE 10 OF 15

11 Q5.D) Write a documented 68K assembly language routine void MakeClockSignal( long int whichclock, short int how_many_pulses) which functions as follows. Using the subroutine call MakeClockSignal(0, 100) would mean that the subroutine would start by setting the A3 clock pin HIGH. Then the pulses coming from the pulse generator (whichclock = = 0) are counted. After 100 pulses (how_many_pulses = = 100), the A3 clock pin is set LOW and the subroutine exits. Using the subroutine call MakeClockSignal(1, 200) would mean that the subroutine would start by setting the A3 clock pin HIGH.. Then the pulses coming from the TMP04 chip (whichclock = = 1) are counted. After 200 pulses (how_many_pulses = = 200), the A3 clock pin is set LOW and the subroutine exits You must make a call to the function void ResetDevice(void) (from Q5C) inside MakeClockSignal ( ) in order to initialize the PI/T and start up thetmp04 chip. 10 marks for this question. You may make 2 basic errors without penalty THERE ARE 10 MARKS AVAILABLE ON THIS PAGE YOUR MARK ESTIMATE / 10 PAGE 11 OF 15

12 Q6. A) The C standard defines the strncat() function as follows char *strncat(char *s1, char *s2, long n) The strncat() function appends not more than n characters (a null character and characters that follow it are not appended) from the array pointed to by s2 to the end of the string pointed to by s1. The initial character of s2 overwrites the null character at the end of s1. A terminating null character is always appended to the result. (The maximum number of characters in the final array pointed to by s1 is strlen(s1)+n+1. The strncat( ) function return the value of s1. Example:- char first[20] = head ; char second[20] = tail ; char *pt; pt = strncat(first, second, 2); putsln(first); Output is headta Write a documented assembly language version of the function strncat() that is compatible with C stack conventions. HINT carefully read the functionality of the function to avoid missing key elements and introducing defects into your code (10 marks). THERE ARE 10 MARKS AVAILABLE ON THIS PAGE YOUR MARK ESTIMATE / 10 PAGE 12 OF 15

13 Q6B) Provide a labelled schematic of the resources of a typical MICRO-CONTROLLER SYSTEM in use to control a Peripheral Interface/Timer device. The schematic should show both internal and external resources processor resources. There should be sufficient detail so that you would be able to use the diagram to explain, using a register transfer language (RTL), how these resources interact to enable the instruction MOVE.B #4, 0x41B010 to operate to place the value 5 into one of the PI/T registers. (5 marks) Q6C Referring to the diagram in Q6B, use a register transfer language (RTL), how these resources interact to enable the WRITEBACK phase of the instruction MOVE.B #4, 0x41B010 to operate to place the value 5 into one of the PI/T registers. (5 marks) THERE ARE 10 MARKS AVAILABLE ON THIS PAGE YOUR MARK ESTIMATE / 10 PAGE 13 of 15

14 Q7) -- 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. Make up a question related to this course AND answer it. (20 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 (around marks). Questions and answers that give a new insight into a concept handled in class will receive a C or a B grade (11 14 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 (14 and up), if answered correctly. A good mark on this question would be 15 or 16 marks out of 20 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 I don t like marking 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 me and leave me thinking that s clever and well thought out or leave me wanting to boast to other instructors about what you suggested -- are more likely to receive higher marks. Page 14 of 15

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16 EXTRA PAGE ---- IN-CASE YOU NEED IT FOR A LONG ANSWER

17 Performance Analysis Sheet Maximum Bonus Marks 5% FINAL EXAM FOR ENCM415, 18 th December, 2001 NAME:- ID#:- Good software engineers keep track of their progress and can estimate their success. In the table below, indicate questions attempted and your estimate of how well you have answered the question. For each estimate that matches the mark you actually receive, you will receive a bonus mark to make up for the time lost answering this section -- Maximum bonus 5 marks MAXIMUM YOUR ESTIMATE OF YOUR PERFORMANCE MARK ATTEMPT ALL QUESTIONS FROM SECTION A SECTION A Q1 20 Circle your expected mark on this question A > 15 > B > 13 > C > 11 > D > 8 > F SECTION A Q2 20 Circle your expected mark on this question A > 15 > B > 13 > C > 11 > D > 8 > F SECTION A Q3 20 Circle your expected mark on this question Bus Activity General Knowledge Translation of C/C++ to 68K assembly code Design -- PI/T with interrupts General Knowledge A > 15 > B > 13 > C > 11 > D > 8 > F ATTEMPT ANY TWO QUESTIONS FROM SECTION B IF YOU ATTEMPT THREE, THE THIRD WILL BE IGNORED SECTION B QUESTIONS ARE INTENDED TO BE SIGNIFICANTLY MORE DIFFICULT THAN SECTION A QUESTIONS SECTION B Q4 20 Circle your expected mark on this question A > 15 > B > 13 > C > 11 > D > 8 > F SECTION B Q5 20 Circle your expected mark on this question A > 15 > B > 13 > C > 11 > D > 8 > F SECTION B Q6 20 Circle your expected mark on this question A > 15 > B > 13 > C > 11 > D > 8 > F SECTION B Q7 20 Circle your expected mark on this question A > 15 > B > 13 > C > 11 > D > 8 > F General Knowledge Code Optimization techniques Design Question Lab. 2 for ENCM415 in 2002 String array handling Microprocessor internals/rtl Write your own question and answer it YOUR ESTIMATE OF YOUR FINAL MARK -- OUT OF 100 / 100 Process management component of the exam 1 Mark bonus if prediction of mark on a question is accurate to +-1 (estimates of unanswered questions excluded) 2 Mark bonus if prediction of final mark on quiz is accurate to +-3 Maximum of 5 Bonus marks To give you an idea of what I would consider the relative difficulties of the questions, here are my expected Class Averages if everybody in the class attempted a particular question SECTION A Q1 -- B- / B Q2 B+ / B Q3 C / C+ (Higher marks available IF you apply your PSP process) SECTION B Q4 -- C / C+ Q5 C- / C Q6 C / C+ Q7 C+ / B- Planned exam mark average in the range 65% -- 68% (C / C+). Add to this the Bonus marks gained (average 3) for knowing what questions you did well and what questions you did poorly will give you 69% -- 71% (C+/ B- / B ) for the final exam EXTRA PAGE