University of Florida EEL 4744 Summer 2014 Dr. Eric M. Schwartz Department of Electrical & Computer Engineering 1 July Oct-14 6:41 PM

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Page 1/14 Exam 1 Instructions: First Name Turn off cell phones beepers and other noise making devices. Show all work on the front of the test papers.

You may use any of your XMEGA documents with limited added material; highlighting and tagging is permissible.

Put your name at the top of each test page and be sure your exam consists of 14 distinct pages. The space provided does not necessarily represent the amount of writing needed.

Read each question carefully and follow the instructions. be with you! The point values for problems may be changed at prof s discretion.

1 Page 1/14 Exam 1 Instructions: First Name Turn off cell phones beepers and other noise making devices. Show all work on the front of the test papers. If you need more room make a clearly indicated note on the front of the page "MORE ON BACK" and use the back. The back of the page will not be graded without an indication on the front. You may use any of your XMEGA documents with limited added material; highlighting and tagging is permissible. You may not use any notes (mine or yours) examples homework labs books calculators computer electronic devices etc. Put your name at the top of each test page and be sure your exam consists of 14 distinct pages. The space provided does not necessarily represent the amount of writing needed. You must pledge and sign this page in order for a grade to be assigned. May the Schwartz In programs the use of comments results in more partial credit. Read each question carefully and follow the instructions. be with you! The point values for problems may be changed at prof s discretion. PropaGator 2: UF s Autonomous Surface Vehicle (Robot Boat with quadcopter) for RoboBoat competition Part of your grade on tests quizzes labs etc. is based not only on solving the problem you are presented with but the manner in which you solve it. For example there is a difference between two programs that meet the given specifications but one is an elegant extensible 20-line solution while the other is an obfuscated 100-line program that also meets the specifications but would be difficult to extend later. Just as your future employer would value the latter program less than the first so will I in grading your assignments. This exam counts for % of your total grade. Unless otherwise stated assume the following: The oscillator frequency is precisely 2 MHz. The code should run on an ATxmega12A1U as configure on the UF utinkerer Development Board without any additional peripherals. PLEDGE: On my honor as a University of Florida student I certify that I have neither given nor received any aid on this examination nor I have seen anyone else do so. PRINT YOUR NAME SIGN YOUR NAME DATE (1 July 14) PropaGator 2 propulsion system Regrade comments below. Give page # & problem # and reason for the petition. Pages Available Points TOTAL 100

2 Page 2/14 Exam 1 First Name [27%] 1. In this problem you will design an expansion to a XMEGA board (like your utinkerer) by adding an input port an output port an SRAM a ROM and a keypad. 16K (16k x ) ROM Addr Range: 0x x = 0b - 0b K (k x ) SRAM Addr Range: 0x - 0x = 0b - 0b Port Addr Range: 0x - 0x = 0b - 0b Port/Memory Blocks ( %) a) Assume that an unknown device or devices takes up address 0x x3 7FFF but that no other external components have yet been added to your XMEGA board. In parts a-e of this problem you will design the circuits to add a 16k x ROM an k x SRAM an - 10 min bit input port an -bit output port and a keypad. The 16k x ROM should be fully address decoded and start immediately after the unknown device(s) i.e. at 0x The k x RAM should be fully address decoded and start immediately following the ROM. The two ports should be partially address decoded at the same addresses and at the most efficient addresses immediately following the RAM. You will also add a keypad using 4 pins (0 through 3) from your input and 3 pins (0 through 2) from output port and resistors if necessary. Fill in the addresses below and draw in port/memory blocks to the right to help you solve this problem. (a & c-e = 1%) (4%) b) If you need an XMEGA CS you can use only CS2. If necessary configure CS2 for this problem. 4 min EBI_CTRL = CS2_BASEADDRH = CS2_BASEADDRL = CS2_CTRLA =

3 Page 3/14 Exam 1 (a & c-e = 1%) 4 min First Name 1. c) Derive any necessary equations for the address part of address decoding i.e. XAddr = f(addresses only). In part e you will design the necessary circuits. (a & c-e = 1%) 4 min d) Derive the control equations that you will need to control the ports and memories e.g. Xctrl = f(xaddr RE WE Reset ). In part e you will design the necessary circuits. Be sure to disable your devices when Reset is true and also to protect your hardware from bad software.

4 Page 4/14 Exam 1 First Name (a & c-e = 26%) 1 1. e) Complete the circuit diagram below as specified in part a. Please USE LABELS instead of wires! Please USE LABELS instead of wires! Add additional components only if necessary (but only resistors and SSI gates e.g. ANDs NORs NOTs etc.). XMEGA = Port K = Port J RE WE ALE1 Port H ALE2 CS2 CLK EBI Reset 16k x ROM A -A 0 D 7 -D 0 OE CS Port Port k x bit RAM A -A 0D7 -D 0 WE OE -bit Flip-Flop D 7 -D 0 Q 7 -Q 0 -bit Latch D 7 -D 0 Q 7 -Q 0 G CS -bit Tri-State In 7-0 Out 7-0 OE * 0 #

5 Page 5/14 Exam 1 First Name (5%) 1. f) Write an assembly language program fragment necessary to determine if the # key is pressed. Store 0x37 into R16 if the key is pressed; otherwise store 0. 6 min Labels Instructions Comments

6 Page 6/14 Exam 1 First Name [1%] 2. You will use the GPIO system in this problem to properly utilize an external interrupt. (3%) a) Write assembly code to set up the interrupt 1 vector for PORTE so that the interrupt service routine PE1_EX_INT_ISR is executed when the selected pin(s) have changed as described in other parts of this problem. Labels Assembly Instructions Comments (7%) b) Assume there is a subroutine INIT_ISR that is called shortly after the start of the program from the main routine. Write an assembly program to initialize the above interrupt for a min falling edge trigger on either bits 3 or 7 of PORTE with a medium priority level. Interrupts should be ready to execute upon returning from this subroutine so be sure to configure all necessary registers. Labels Assembly Instructions Comments

7 Page 7/14 Exam 1 First Name (%) 2. c) Write the entire program to do the following. Assume that PORTF is connected to min active-high LED circuits (as in your lab 2). Use the LEDs at PORTF to count the number of PORTE interrupts that occur. You can insert the code from parts a and b by writing INSERT_a or INSERT_b where you would like the code to be placed. (There is more room if necessary on the next page.) Labels Instructions Comments

8 Page /14 Exam 1 First Name 2. c) (continued) Labels Instructions Comments

9 Page 9/14 Exam 1 First Name [19%] 3. Assume an XMEGA subroutine named Sub_Robot is located at address 0xD37B. Write the instruction at address 0x73E2 for appropriately initiating subroutine execution in the empty box below left; if possible use an rcall rather than a call. Write the stack pointer initialization instruction(s) in the boxes below right. Initialize the stack pointer at an appropriate location in internal XMEGA SRAM. (3%) a) Address Subroutine execute instruction Stack pointer initialization instructions 3 min nop 0x73E1 0x73E2 0x73 nop (2%) b) Describe the stack on the XMEGA as it relates to a subroutine and program addresses. 3 min (7%) c) For each of the below descriptions draw the stack. In each case show an arrow ( ) at the 7 min location of the stack pointer. On the far left show (valid) addresses for each of the used stack locations. Also provide the values requested at the bottom of these tables. Addresses 1) after the stack is initialized 2) at the start of the subroutine execution 3) after push R16 (R16 = 0x42) 1-After Init 2- at start of subr 3- after push R16 4) after a push R25 (R25 = 0xAB) 5) after pop R16 6) after the return from the subroutine 4- after push R25 5- after pop R16 5- After return SP = SP = SP = SP = SP = SP = PC = R16 = PC =

10 Page 10/14 Exam 1 First Name (2%) 3. d) Describe the stack on the XMEGA as it relates to an interrupt service routine and program addresses. (5%) e) For an interrupt service routine describe what if anything should be pushed and 5 min popped from the stack. Give examples in the table below to help demonstrate your description. Labels Instructions Comments

11 Page 11/14 Exam 1 First Name [1%] 4. The XMEGA on your utinkerer board has a maximum processing speed of 32 MHz available if an external oscillator is used. Assume that a 25 MHz oscillator is utilized for this problem. Hint: 1/25 MHz = s = s = 0.04 µs. (2%) a) Calculate the number of cycles that are necessary to create a 100 µs (= 0.1 ms) delay. [For parts b through e assume every instruction takes precisely 1 µs.] (3%) b) Assume that subroutine Delay_100us is already written and available. Write a 3 min subroutine Delay_10ms to delay ~10ms below. State any assumptions in comments. Note µs = 10 ms Labels Instructions Comments (3%) c) Write a subroutine Delay_Vx10ms to delay V 10 ms for V=1 to 255 ( 10 ms to 3 min 2.55 s). Assume that the V value is in register R16 upon entry into this subroutine. Labels Instructions Comments

12 Page 12/14 Exam 1 (2%) 4. d) Explain why the delay in part c would not be precise. First Name (%) e) Write a subroutine to appropriately initialize PortD and PortE and a program fragment min (that will never end) to do the following. If bit 5 on PortD is high toggle only PortE bit 6 every 370ms; if bit 5 on PortD is low toggle only PortE bit 6 every 730ms. Do not change any of the other bits of PortD or PortE. Use subroutine Delay_Vx10ms! Labels Instructions Comments InitPorts: Tog_Frag:

13 Page 13/14 Exam 1 [15%] 5. Answer the following short questions. (1%) a) What is the purpose of the Dragon on your utinkerer board? First Name (2%) b) Describe two ways to setup a table end boundary? (2%) c) Describe the differences of data memory and program memory (with respect to your XMEGA) and what each is used for in a program. 3 min (2%) d) In assembly language give examples of each of the described assembler directives: (a) give a register an alternate name (b) give an alternate name to a constant (c) store a constant (d) reserve space for a variable? a) b) c) d) (2%) e) What is the purpose of the EBI system?

14 Page 14/14 Exam 1 First Name (2%) 5. f) Draw an LED circuit diagram for a microprocessor output that will light up an LED when the active-low signal X(L) is true. The circuit should do nothing else. (The LED circuit design symbol is shown below.) (2%) g) Draw a switch circuit diagram for a microprocessor input Y(H). The circuit should do nothing else. (The switch circuit design symbol is shown below.) Use the shown switch position as the true position. [5%] 6. With the XMEGA on our utinkerer we use shared pins in the External Bus Interface 5 min mode namely A15: are shared with A7:0. Draw a timing diagram for a read cycle for our processor if the shared pins were instead A15: A7:0 and D7:0.

University of Florida EEL 3744 Spring 2017 Dr. Eric M. Schwartz Department of Electrical & Computer Engineering 22 February Mar-17 1:44 PM

University of Florida EEL 3744 Spring 2017 Dr. Eric M. Schwartz Department of Electrical & Computer Engineering 22 February Mar-17 1:44 PM Page 1/11 Exam 1 Instructions: Turn off cell phones beepers and other noise making devices. Show all work on the front of the test papers. If you need more room make a clearly indicated note on the front