University of Florida EEL 4744 Spring 2013 Dr. Eric M. Schwartz Department of Electrical & Computer Engineering 28 March Jun-13 6:18 PM

Size: px

Start display at page:

Download "University of Florida EEL 4744 Spring 2013 Dr. Eric M. Schwartz Department of Electrical & Computer Engineering 28 March Jun-13 6:18 PM"

Franklin Jones
5 years ago
Views:

First Name 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.

1 University of Florida EEL 4744 Spring 2013 Dr. Eric M. Schwartz Department of Electrical & Computer Engineering 2 March Jun-13 6:1 PM Page 1/14 Exam 2 Instructions: Turn off cell phones beepers and other noise making devices. First Name 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 necessary. BEAT FGCU! You must pledge and sign this page in order for a grade to be assigned. I n programs the use of comments results in more partial credit. May the Schwartz Read each question carefully and follow the instructions. The point values for problems may be changed at prof s discretion. be with you! 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: Go Good * 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. Gators! luck! * 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 (2 Mar 13) Regrade comments below. Give page # & problem # and reason for the petition. Pages Available Points TOTAL 100+6

2 Page 2/14 Exam 2 [29%] 1. In this problem you will design an expansion to a utinkerer board by adding k x of ROM k x of SRAM an -bit LCD a single input port and a single output port. (1%) a) Assume that the XMEGA s CS0 has been configured to work between 0x and 0x37 FFFF and that no external parts have yet been 7 min added to your utinkerer but that no addresses beyond 0x37 FFFF can be used. Addresses 0x x37 1FFF are reserved for future use. Starting at address 0x add k x ROM (using only 4k x ROM chips) followed by k x SRAM (from a 32k x SRAM chip) followed by a memory-mapped -bit LCD with 4k images (i.e. k total address range) and then the two ports. The number of images for the I/O ports should minimize the required hardware. Use full address decoding for the ROM and SRAM. First Name You MUST fill in the table below draw in port/memory blocks (above right) and fill out parts b and c to help you solve (and the TA grade) this problem. Port/Memory Blocks K (k x ) ROM Addr Range (using only 4k x ROMs): 0x x37 = B - B K (k x ) SRAM Addr Range (of a 32k x SRAM): 0x37-0x37 = B - B -bit LCD with 4k images i.e. k total Addr Range: 0x37-0x37 = B - B Port Addr Range: 0x37-0x37 = B - B (3%) b) Derive any necessary equations for the address decoding. For this problem you can NOT use any additional built-in chips selects on the XMEGA. 4 min (2%) c) Derive the control equations that you will need to control the ports and memories. In part d you will design the necessary circuits. 3 min

3 Page 3/14 Exam 2 First Name (17%) 1. d) Complete the circuit diagram below as specified in part a. Please USE LABELS instead 10 min of wires! Please USE LABELS instead of wires! Add additional components only if necessary (but ONLY SSI gates (PLDs) e.g. ANDs NORs NOTs etc.). = Port K = Port J XMEGA Port H RE WE ALE1 CS0 Reset Port C Port D Port Port 12 4k x bit ROM A 11 -A 0 D 7 -D 0 OE CS 15 32k x bit RAM A 14_ -A 0 D 7 -D 0 WE OE CS 12 4k x bit ROM A 11 -A 0 D 7 -D 0 OE CS Crystalfontz LCD RS=C/~D R/~W DB 7 -DB 0 E -bit Latch D 7 -D 0 Q 7 -Q 0 G -bit Flip-Flop D 7 -D 0 Q 7 -Q 0 -bit Tri-State In 7-0 Out 7-0 OE

4 Page 4/14 Exam 2 First Name (2%) 1. e) What special registers do you have to use to read/write data from addresses beyond 0xFFFF in DATA memory (i.e. not PORGRAM memory)? 1 min (2%) f) Why would you want to use an XMEGA CS (like CS0) rather than the CPLD? 2 min (2%) g) When would you need to use a CPLD in addition to a CS? 2 min (4%) 2. Draw two circuit diagrams one of a switch circuit with output A(H) and another of an LED 3 min circuit with input B(L). Draw the switch in the true position. Label the output and the input respectively.

5 Page 5/14 Exam 2 First Name [15%] 3. You are trying to build a robot lawnmower but you must work with other students software 4 min and the equipment that you are given. Assume that another team member has setup a high level interrupt for an ADC (analog to digital converter) pin. Your team has purchased (and you must use) an extremely slow LCD. The kill switch (which when pressed immediately stops the lawnmower for moving and the blade from spinning) is tied to an external interrupt that is set at medium level. (4%) a) Create a flowchart or pseudo code for the following specification. (In part b you will add instructions to some instructions that have already been written.) 11 min Assume the necessary pre-program initializations and other necessary software initializations have already been written. The kill switch interrupt should fire and kill the lawnmower robot as QUICKLY as possible. NOTHING is more important! Maximize the time spent doing autonomous work i.e. cutting the grass. The main routine should have a continuous loop that makes the lawnmower do autonomous work i.e. cut the grass. You are given the following (already written) four subroutines with specifications: o The ADC uses an interrupt. READ_ADC is a subroutine that reads the -bit ADC value into R17. o The OUT_LCD subroutine converts the value in R16 to a string and then sends the string to display on the LCD screen. R16 is the last read ADC value. (Assume that the OUT_LCD routine does the necessary binary to ASCII conversions to change the byte into a voltage.) This subroutine takes a long time to complete; it does not end until the LCD shows the new string and is ready for another character to be sent to the LCD. Only output to the LCD when another ADC value is read. o o The WORK subroutine will cause the robot to mow the lawn (i.e. cut the grass). This subroutine will always run for two seconds (not including interrupts) which means that the LCD won t start updating for up to 2 seconds. Maximize the time performing this function. KILL is a subroutine that stops all lawnmower motors. This is the most important function! NOTHING is more important! ADC_ISR is the interrupt service routine for the ADC. You do not have to clear this interrupt s flag. EXT_ISR is the interrupt service routine for the kill switch s external interrupt.

6 Page 6/14 Exam 2 15 min (9%) 3. b) Add the necessary instructions to meet the specifications in part a. First Name MAIN: Labels Instructions ; Normal initializations are done for you ; Interrupts systems are configured for you and ready to go LOOP: ADC_ISR: EXT_ISR:

7 Page 7/14 Exam 2 First Name (2%) 3. c) If you could what specifications should you change to simplify the code structure and more appropriately solve the key requirements of the problem? 3 min BONUS (optional) (+3%) d) Explain how you can have write to the LCD without wasting so much processor time. 5 min BONUS (optional) (+3%) 4. Similarly to the LCD above determining when a keypad button is pressed is very slow and 5 min wastes a lot of processor time. Assume that the keypad has pull-up resistors on the four rows which are processor inputs; the processor outputs go to the four columns. Explain how you can use the keypad in such a way that it uses significantly less processor time. (You can ignore switch bouncing in your answer to this problem.)

8 Page /14 Exam 2 First Name [25%] 5. A student wrote the following program to initialize an external SRAM and then check if the SRAM functions properly (or if errors occur). If there is an SRAM error then the student 25 min send an E through USARTC0. Find and correct all of the errors in the below program. You can either correct the errors in place or refer to the line numbers to correct them on the next page. (Assume USARTC0 is initialed with a call in INIT_UART which is available but not shown.) include "ATxmega12A1Udef.inc".set SRAM_BEGIN = 0x450000;.set SRAM_END = 0x451FFF;.org 0x0000 rjmp MAIN.org 0x0100 MAIN: rcall INIT_EBI rcall INIT_UART ; Assume this exists rcall INIT_SRAM rcall SRAM_store ; Write then read data in all SRAM ; addresses SRAM_Store: ldi R16 0xFF st Z R16 ld R16 Z cpi R16 0xFF brne ERROR inc Z cpi ZH 0x1F brne SRAM_Store cpi ZL 0xFF breq SRAM_Store ;******************* ;Send an E out to USART ERROR: ERROR_POLL: lds R16 USARTC0_STATUS sbrc R17 1 breq ERROR_POLL sts USARTC0_DATA 'E' ret ;******************* INIT_EBI: push R16 push R17 ldi R16 0x13 sts PORTH_DIR R16 ldi R16 0x13 sts PORTH_OUT R16 ldi R16 0xFF sts PORTJ_DIR R16 ldi R17 0x01 sts EBI_CTRL R17 pop R16 pop R17 ret ;******************* INIT_SRAM: ldi ZH HIGH(EBI_CS0_BASEADDR) ldi ZL LOW(EBI_CS0_BASEADDR) ldi R16 ((SRAM_END >> ) & 0xF0) st Z+ R16 ldi R16 ((SRAM_END >> 16) & 0xFF) st Z R16 ldi R16 0x1D sts EBI_CS1_CTRLA R16 ldi ZH HIGH(SRAM_BEGIN) ldi ZL LOW(SRAM_BEGIN)

9 Page 9/14 Exam 2 First Name (25%) 5. (Continued) Correct any software that you did not correct previously. Use the line 6 min numbers to refer to the original and correct code. If for example line 95 is replaced with three lines then label the replacement lines 95a 95b and 95c.

10 Page 10/14 Exam 2 First Name [27%] 6. In the next several sections you will write the most of a program to send a message out of the 4 min USARTD1 (NOT USARTC0) serial port of your utinkerer every time a # (ASCII value 0x23) is received. This code should never stop executing but should be interrupt driven so that other functions could be running simultaneously. The program will also include a counter that is triggered by interrupt whenever a character is transmitted out of USARTD1. In the next several sections you will write two USART initialization subroutines a receiver interrupt service routine (RX_ISR) and a transmitter interrupt service routine (TX_ISR) and define all the necessary registers constants and variables. Assume that the main routine and the OUT_STRING function have already been written. Assume that the main routine calls the subroutines of parts a and b i.e. INIT_USART and INIT_USART_INTR and then runs an endless loop. (4%) a) Define all desired register definitions constants variables and non-instruction software 5 min that you will need in the subsequent sections. You will need to return to this part while completing each of the next sections of this problem. Note: A few entries have already been made for you. Please make sure to fill in the value for BSEL. Labels Instructions Labels Instructions.equ POUND = 0x23.equ ESC = 0x1B.equ BSCALE = -1.equ BSEL = STRING:.org 0x100.db "4744 is Great" 0x00

11 Page 11/14 Exam 2 First Name (5%) 6. b) Write a USARTD1 initialization subroutine (INIT_USART) to turn on the transmitter turn on the receiver use -bits of data odd parity 2 stop bits and run at Hz. Show your calculations for the baud rate related values given that BSCALE = -1. Also appropriately define any necessary initialization values e.g. BSel back in part a. Labels Instructions Comments

12 Page 12/14 Exam 2 First Name (3%) 6. c) What is the minimum time it would take to transmit a table of 100 bytes assuming that interrupts were used? Show your work. 4 min (3%) 2. d) Write a subroutine (INIT_USART_INTR) to appropriately initialize the USARTD1 interrupt system for the serial receiver AND transmitter. This should anything necessary 2 min to be able to use the interrupt when this routine is completed. Assume the interrupt service routines are called RX_ISR and TX_ISR. Also appropriately define any necessary initialization values (including initializing the interrupt service routine vector) e.g. USARTD1_RXC_VECT back in part a. Labels Instructions Comments

13 Page 13/14 Exam 2 First Name (4%) 6. e) Write an interrupt service routine (RX_ISR) to read a single character. If the character is 6 min a # (see part a) call subroutine OUT_STRING; otherwise do not call OUT_STRING. Also appropriately define any necessary initialization values back in part a. Labels Instructions Comments

14 Page 14/14 Exam 2 First Name (%) 6. f) Write an interrupt service routine (TX_ISR) to increment a counter whenever a character is transmitted on USARTD1. The counter must persist between transmits. If the last min received character is ESC (see part a) reset the counter to zero. Also appropriately define any necessary initialization values back in part a. Labels Instructions Comments

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

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