Mahmood:

I think you have the correct view point about the "randomness" factor. It only really has to be "good enough". I do think as Kai pointed out that the bursts of 3 in a row could be problematic. I messed around with Keil C51 using the debugger in the simulator and created the following small program:

#include <stdlib.h>

unsigned char xdata array[300];

void main(void)
{
    int r;
    unsigned char rr;
    int i;

    for(i=0; i<300; i++)
    {
        r = rand();
        rr = ((r / 7) % 8) + 1;
        array[i] = rr;
    }
    while(1)
    {
    }
}

I then exported the data out of the µVision2 Watch Window for the array[] variable into Excel and created a chart similar to yours as shown below:



Is this more "random"? Good question.
Does it have a "pattern"? Maybe.
Is it "good enough"? I think so!!

Michael Karas