Lagged Fibonacci Pseudo-Random Generator

If you need a pseudo-random number generator which works regardless of the coresize, a Lagged Fibonacci generator is one of the better options.

Here's an implementation in 3 instructions with _rndj fixed at 1. _rndk can take the values 3, 4, 6, 7, 15, 22, 60 or 63 depending on the period required. With _rndk = 4 and coresize 8000, the period is 31200.

For more variations, see the Wikipedia article on Lagged Fibonacci generators.

           _rndk  equ 4

random    mov.a  >rdata,        random_out
          mod.ab #_rndk,        rdata
          add.a  *stack,        @rdata

rdata     dat    3711,           0
          dat    1674,           0
          dat    4323,           0
          dat    7835,           0