Korg Poly800/EX800 Users

For those interested check out wikipedia
http://en.wikipedia.org/wiki/Linear_congruential_generator

The waveform generation code has to be fast and it has to generate not
just random but triangle, sawtooth, sine, square PWM as well.

So I chose to pick a recurrence relation that was fast and "sounded"
random and it does that "reasonably" well. It is by no means random it
just sounds somewhat random.

Mike.

--- In korgpolyex@yahoogroups.com, ASSI <Stromeko@...> wrote:
>
> On Samstag 20 September 2008, Atom Smasher wrote:
> > assembler?!?! i should have known.... and i've always considered C
> > a low level language...
> 
> In C:
> 
> ((m ? m : -m) << 1) + 43;
> 
> Better? :-)
> 
> > despite the verbose comments (is all of the code commented that
> > well?) i can't follow it. can you give a brief explanation?
> 
> It is somwthing that looks like a LFSR, but isn't (the feedback is 
> actually missing).  When I find some time I'll simulate to see what 
> the cycle length is for different seed values.
> 
> > On Thu, 18 Sep 2008, korgpolyex800 wrote:
> > > Here's my pseudo random number generator.
> > >
> > > It is by no means very random.
> > >
> > > ; my pseudo random number generator - used for the LFO randomiser
> > > ; returns a random number in A
> > >
> > > RANDOMIZE:	push	h ; save HL
> > > 		lxi	h, M_RANDOM ; point at the previous value (seed)
> > > 		mov	a, m ; put the seed value into A
> > > 		cpi	0 ; check for seed equals zero
> > > 		jnz	RANDOMIZEA ; if seed is zero jump to randomizea
> > > 		cma ; compliment A
> > > 		mov	m, a ; put A back into seed
> 
> This line is redundant because you save the seed again later on.
> 
> > > RANDOMIZEA:	rlc ; rotate left through carry
> > > 		adi	43 ; add 43 offset
> > > 		mov	m, a ; save in seed
> > > 		pop	h ; load HL
> > > 		ret ; return with pseudo random in A
> > >
> > > I would be more than happy for you to suggest something better as
> > > long as it doesn't add any CPU cycles. :-)
> 
> 
> Achim.
> -- 
> +<[Q+ Matrix-12 WAVE#46+305 Neuron microQkb Andromeda XTk]>+
> 
> Factory and User Sound Singles for Waldorf Blofeld:
> http://Synth.Stromeko.net/Downloads.html#WaldorfSounds
>