Lab 9

11/22 and 11/23


Blinking Lights!!

In preparation for the holidays, your job is to create 2 different
patterns of blinking lights.  Two really easy ones would be doing
rotates of a single on (or off) bit.  You can only use 1 really easy
one for this assignment.

For this assignment, you will be using the TICSEC (or USERTICK, or
some multiple of USERTICK) value so that you can move forward in your
cycle of patterns once per second (or some other time you decide upon).

Choose which pattern to do according to the switches.  For example, as
long as the LSB switch is off, do pattern 1, otherwise do pattern 2.


Notes:

1.  Next week, we will combine this program with your fibonocci
    program, so that your LED program is interrupt driven (according
    to the timer interrupt), and the external interrupt button will be
    used to switch between your 2 choices.

2.  Depending on your patterns, you may need to notice each time
    the switch is changed, so that you can load some initial
    configuration.  Do this by storing the previous switch pattern
    somewhere, and keep checking in your polling loop whether or not
    the switches changed and whether or not the clock changed
    appropriately. 

3.  In this lab, it is OK to keep your bit positions in, for example,
    accumulator A.  For the interrupt version, you will need to keep
    the bit pattern in memory becuase accumulator A is used by your
    fibonocci program.

4.  Use polling to determine when to update the lights (ie, keep
    checking USERTICK or TICSEC until it changes to (or past) the
    appropriate value).

5.  Note that TICSEC and USERTICK are 16-bit values, so can
    wrap-around after running for a while.  Also, if your time to
    check thigns takes longer than a USERTICK, your program might not
    see all consecutive numbers in the USERTICK register!  

Checkoff (in your lab session):

  check -  One pattern of blinking lights not controlled by the switches.
  check    As described above
  check +  4 patterns that are particularly interesting or
	   variable speed patterns, or someting else original.
  


Submit:
  lights.asm  Your program
  readme      Description of your patterns and how you decide what
	      time to update them.