Chase H.Q.: Routine at 9618

9618: Random number generator

Output
A	Random byte

rng_seed

9618

DEFB $7B,$2D,$E9

Seed / initial state

This entry point is used by the routines at animate_meters, sfx_cornering, setup_transition, print_chatter, smash_handler, spawn_cars and main_loop_18.

rng

961B

LD HL,$9618

Point at rng_seed / state bytes

961E

LD A,(HL)

rng_seed[0] -= 141

961F

SUB $8D

9621

LD (HL),A

9622

INC HL

rng_seed[1] += 3

9623

INC (HL)

9624

INC (HL)

9625

INC (HL)

9626

ADD A,(HL)

A = rng_seed[0] + rng_seed[1]

9627

INC HL

9628

RRCA

Rotate A by 1

9629

RRC (HL)

Rotate rng_seed[2] by 1

962B

ADD A,(HL)

rng_seed[2] += A

962C

LD (HL),A

962D

RET

Return