Subject: Re: [stella] Random number generation on 2600? From: Chris Wilkson - MCD <cwilkson@xxxxxxxxxxxxx> Date: Sun, 23 Mar 1997 20:00:12 -0800 (PST) |
Erik, You might try incrementing one of the timers every so often. Maybe during vblank. Hmmm...decrementing would work better. In case the timer happens to be zero, it wouldn't always give a value of zero when you read it. I don't have any docs here at work, so I don't know if this is feasible. I don't think you can actually use the DEC instruction, because the timers are write only. Not sure on this. If so, the code below only costs 12 proc cycles, I think. ... ... LDA INTTIM ; get timer value SBC SEED ; subtact preset seed value. don't care about carry. STA (timer) ; store new value in timer of your choice ... ... > > Any hints on how to go about creating a pseudo-random number generator on > the 2600? True random numbers seem pretty difficult if not impossible (as > with most assembly languages), but one can get a seed and plug it into an > algorithm to get pseudo-random numbers. On the PC, it's easy to use the > current time for the seed (all BASIC programmers know RANDOMIZE TIMER), but > that's not there on the 2600.. anyone have a good method for getting a seed > and/or a good algorithm that works well on the 6502? thanks! > > -- > Archives available at http://www.biglist.com/lists/stella/archives/ > E-mail UNSUBSCRIBE in the body to stella-request@xxxxxxxxxxx to be removed. > -- Archives available at http://www.biglist.com/lists/stella/archives/ E-mail UNSUBSCRIBE in the body to stella-request@xxxxxxxxxxx to be removed.
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