EE 308

Exam 1

February 13, 1998

Name:

 

You may use any of the Motorola data books. No calculators allowed. Show all work. Partial credit will be given. No credit will be given if an answer appears with no supporting work.

  1. Show the value in accumulator A and the indicated condition code flags after an HC11 carries out the indicated instructions. Before the first instruction in each part, assume all the flags are zero.

    2.

    (a)

     

    ACCA

    N

    Z

    V

    C

    ldaa #0x7c

    7c

    0

    0

    0

    0

    adaa #0x84

    00

    0

    1

    0

    1

     

    (b)

     

    ACCA

    N

    Z

    V

    C

    ldaa #0xa7

    a7

    1

    0

    0

    0

    adaa #0x95

    3c

    0

    0

    1

    1

    (c)

     

    ACCA

    N

    Z

    V

    C

    ldaa #0x3e

    3e

    0

    0

    0

    0

    adaa #0x6d

    ab

    1

    0

    1

    0

     

    (d)

     

    ACCA

    N

    Z

    V

    C

    ldaa #0x6e

    6e

    0

    0

    0

    0

    suba #0x92

    dc

    1

    0

    1

    1

    (e)

     

    ACCA

    N

    Z

    V

    C

    ldaa #0x00

    00

    0

    1

    0

    0

    suba #0x92

    6e

    0

    0

    0

    1

     

  2. Convert the following eight-bit hexadecimal numbers to decimal numbers.

    		3.

    Hex

    Unsigned

    Decimal

    Signed

    Decimal

    (a)

    27

    39

    39

    (b)

    AC

    172

    -84

    (d)

    7F

    127

    127

     

     

  3. The following shows some data in an HC11’s memory. Reverse assemble the first seven instructions starting at address 0x0100. That is, write down the op codes and operands which the hex numbers represent. Also indicate the starting address of and addressing mode used by each instruction. I’ve done the first instruction for you.

    		4.

    0

    1

    2

    3

    4

    5

    6

    7

    8

    9

    A

    B

    C

    D

    E

    F

    0100

    8E

    01

    2F

    CE

    00

    10

    DC

    23

    3C

    BD

    01

    1A

    38

    20

    F4

    DE

    0110

    20

    EC

    02

    BD

    01

    1E

    96

    2C

    C6

    1A

    94

    10

    8B

    0C

    88

    AA

    0120

    39

    FE

    12

    34

    CC

    33

    44

    5C

    E7

    0A

    B6

    FF

    E2

    B7

    E0

    15

    Starting

    Address

    Op Code

    Operand

    Addressing

    Mode

    0x0100

    lds

    #0x012F

    IMM

    (a)

    0x0103

    ldx

    #0x0010

    IMM

    (b)

    0x0106

    ldd

    *0x23

    DIR

    (c)

    0x0108

    pshx

    INH

    (d)

    0x0109

    jsr

    0x011A

    EXT

    (e)

    0x010C

    bra

    -12

    REL

    (f)

    0x010D

    pulx

    INH

    0x010F

    ldx

    *0x20

    DIR

     

  4. Using the same data in the HC11’s memory as in Problem 3, indicate the values in the registers after the HC11 executes the following instructions. Also, write down the number of cycles needed to execute each instruction.

    5.

    Instruction

    A

    B

    D

    X

    Y

    SP

    Cycles



    00

    00

    0000

    0000

    0000

    0127

    (a)

    ldx #0x0125


    0125

    3

    (b)

    ldd 0x0125

    33

    44

    3344


    5

    (c)

    addb 4,x

    4E

    334E


    4

    (d)

    eora #0x55

    66

    664E


    2

    (e)

    puly



    E70A

    0129

    6

    (f)

    rts




    012B

    5

     

     

  5. What happens to the stack, stack pointer and program counter when you execute the instruction

    6. jsr 0x0125

    Before the instruction is executed assume the program counter is 0x0100 and the stack pointer is 0x01FF.

    The address of the next instruction (0x0103) will be pushed onto the stack – 0x03 will go into memory location 0x01FF, and 0x01 will go into memory location 0x01FE. The stack pointer will be decremented by two to 0x01FD. The program counter will be loaded with the new instruction address 0x0125.

  6. Write a flow chart and assembly language program to meet this specification: K1 and K2 are sixteen-bit unsigned variables.

START PROGRAM

IF K1 < K2

THEN PORTB = 0

ELSE PORTB = 127

ENDIF

END PROGRAM

Make sure this is a complete assembly language program – be sure to include .org statements, etc. Make sure the program will be placed in the HC11’s RAM. K1 and K2 should be located at 0x1010 and 0x1012 respectively.

Special things to look for: 16-bit registers should be used for K1 and K2. Branches should be done with unsigned instructions (e.g., blo or bhs).

 

One way:

 
K1    = 0x1010
K2    = 0x1012
PORTB = 0x1004

      .area  CODE (ABS)
      .org   0x0100
      ldx    K1
      cpx    K2
      blo    l1
      ldaa   #127
      staa   PORTB
      bra    l2
l1:   clr    PORTB
l2:   swi

Another way:

PORTB = 0x1004

      .area  CODE (ABS)
      .org   0x0100
      ldd    K1
      cpd    K2
      blo    l1
      ldaa   #127
      staa   PORTB
      bra    l2
l1:   clr    PORTB
l2:   swi

      .area  DATA (ABS)
      .org   0x1010
K1    .ds    2
D2    .ds    2