ROLL THAT DICE......RANDOMLY

This assignment is to be attempted on an individual basis. If your code is unique and does

something a bit random looking with the DICE...you will pass the assignment. If two people

submit exactly the same code....thats a problem. What are the chances of that! (Obviously

the basic example code I will supply is not enough to just give me back). The max value for

this assignment is 15%. (Very generous!). But I will on the lookout for plagiarism.

So the best solution for this problem is to have some fun doing it yourself!

The problem:

I want you to develop a program that rolls a dice and gives a random result. I will leave the

specific approach to yourself. However, I would suggest that the start of the DICE ROLL is

done by using a switch at PORT A.

When and how the rolling stops I will leave to you to decide.

What you should remember is that the process in the simulator may appear a bit slow, but

would appear much faster in a real system.....and we may get to look at that. So dont worry

if the process appears a bit slow.

The appearance of a DICE ROLLING (changing) is not essential....but looks good if you could

incorporate into your program and will earn credit. Look at the example programs. The

DICE_DEMO_1 file simply changes from 1 6 -1 -and keeps repeating. That is NOT random.

The more important aspect of this program is to ensure that when the DICE stops rolling,

the number that is displayed appears as random as possible.

To help with this there is a nice little program in the book that generates pseudo random

sequences. There is an error in the book code. But I have uploaded the correct code to

Bright Space. This is example 3.5 in KATZEN and I have referred to it in lab class. I include

the section below for you convenience. (Note the code error is

MOVWF TEMP,F

).

A few points to note......if you run the PRBS_1 program with the DICE connected, in a

simplistic manner as in the example I supplied, you will NOT output a very random number.

This is because only a limited number of the generated codes will change the DICE. Run and

step thro this program and you will see what I mean. Also, it starts...(seeded) by the same

value 1 every time it is run. This is more or less the code form the book but just includes a

few modifications such as calling the code as a subroutine.

The seeding (initial value) does not have to be 1....

but cannot be zero

. Now thats a hint at

how you could increase randomness? Note the following comment from Wiki

A pseudorandom number generator's number sequence is completely determined by the

seed: thus, if a pseudorandom number generator is reinitialized with the same seed, it will

produce the same sequence of numbers

.

The choice of a good random seed is crucial in the field of

computer security

. When a

secret

encryption

key

is

pseudorandomly

generated

, having the seed will allow one to

obtain the key. High

entropy

is important for selecting good random seed data.

[1]

........

Random seeds are often generated from the state of the computer system (such as

the

time

),

I suggest you look at something, maybe on YouTube, about the idea of PRBS to give you the

flavour of what you are doing. For those amongst you who pursue computer or

communications engineering you are likely to use PRBS concepts again. In fact the random

number codes generated can be useful for generating random tables of data for some of our

exercises. The concept is often used in relation to testing systems. You may even figure out

a more sophisticated approach to generating random sequences.

I am leaving it open to you to design a solution using some imagination. However, the

submitted assignment must comply with the following guidelines.

1.

A short written description of the technique you are using in the program, about a

paragraph.

2.

A flowchart outlining the key steps involved. The low-level details in subroutines do

not need to be described in the chart, but the subroutine calls should be clearly

referred to.

3.

The program should be modular i.e. be written in definite sections using using

subroutines. Or to put it another way...have a good structure.

4.

The code should be commented.

5.

Also include 3 screen shots of the simulator in step mode executing key segments of

your program and state what the action is.

6.

As with the other lab assignments all of the above should be inserted into a Word

Doc for submission