Lab 10

Week of November 29

Interrupts

This lab requires a combination of your Fibonacci (or Fib & Sum
Squares) program with external and real-time interrupts.

If your Fibonacci program is not running, now is your chance to get it
going to get a few extra points.  Alternatively, you can run a simpler
program at the same time as real-time interrupts.

The idea this program is to have your basic program doing some
calculation based on the switch inputs.  Whenever an appropriate
interrupt comes through, the interrupt routine will be called to
update the LEDs.

The two interrupts that we will be using are:

1.  The external interrupt request

    To use this, you need to change the jump address at location
    ISR_JUMP15 to be a jump to your own routine.  You can do this by
    writing the address of your routine to ISR_JUMP15 and ISR_JUMP15+1
    when your program starts up.  (ISR_JUMP-1 has the jump opcode,
    which is why the table addresses go up by 3 bytes each entry.)

    Because the HC 11 hardware takes care of pushing all registers
    onto the stack during an interrupt, there's very little to worry
    about during interrupt processing.

    Whenever the external interrupt request is pressed, you must
    change sequences going out to the LED.  There must be more
    variation between the sequences than just the initial
    configuration (i.e., the two sequences cannot be running an
    identical sequence of instructions during each update).

2.  The pulse accumulator input

    The pulse accumulator can be used to count clock cycles from the
    timer (which is reserved for the system use, for example in
    updating USERTICK).  The pulses from the timer occur in 4.096ms
    increments.

    The pulse accumulate or will provide even interrupt either during
    each count, or whenever a certain number (up to 256) have
    occurred, or both (see page 11-6).  Both interrupt sources have
    entries in the jump table that you can also modify.

    To use the pulse accumulator, you must write to the PACTL control
    register a bit configuration that sets Port A bit 7 to output,
    turns on the pulse accumulator, and sets external event
    accounting.  The two RTR1 and RTR0 fields should be unchanged, so
    read the register, change the bits that you wish to change, and
    write the register back.

    Also, you'll need to decide whether you want interrupts during
    each pulse or for each group of pulses, and set TMSK2 and TFLG2
    appropriately.  Notes carefully the sentences that start
     "Before leaving the interrupt service routine..."

The interrupt service routines


1.  During an external interrupt, you'll need to change some state
    (memory location) to indicate which LED output routine you are
    using.  You may also need to do the first iteration of that
    routine, or load the appropriate starting values into the LEDs.

2.  During each pulse accumulator interrupt, you will cycle to the
    next LED configuration.


While all of this is running, you will also be executing the Fibonacci
program based on the input from the switches.


Reviced Grading:

++: Fully working during checkoff, with really neat light patterns, 
    features, and Fibonacci program.  Great readme and code on
    submit. 

 +: Excellent light pattern, reasonable Fibonacci or other program,
    and great readme and code on submit. 

 x: Good light patterns, reasonable Fibonacci or other program, and
    good readme and code on submit.

    -or, without real-time interrupts-

    A more complicated and creative interaction between external
    interrupt button and lights than a check-, with an excellent
    readme.  For example, switch bit 7 is not used for fib, but
    instead to indicate which of 2 patters should be used, and
    external interrupt steps the pattern while fib program is running,
    and the external interrupt switch is debounced as discussed in
    class. 

 -: Passable demo, working submitted code, and good readme.
    External interrupt used to cycle between patterns or to step a
    single pattern.


Submit:  by 9pm, Friday December 3.
   
  README:  
     1. A description of your interrupt procedures
     2. How you achieved the time steps that you decided 
        to use
     3. A complete discussion of any differences between 
	the code that you are submitting and the code that
	you had checked off. 
     3. Any general comments on the lab

  intr.asm 

Checkoff in your lab section on Wednesday or Thursday.