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Random:: ; 2f8c
; A simple hardware-based random number generator (RNG).
; Two random numbers are generated by adding and subtracting
; the divider to the respective values every time it's called.
; The divider is a register that increments at a rate of 16384Hz.
; For comparison, the Game Boy operates at a clock speed of 4.2MHz.
; Additionally, an equivalent function is executed in VBlank.
; This leaves a with the value in hRandomSub.
push bc
ld a, [rDIV]
ld b, a
ld a, [hRandomAdd]
adc b
ld [hRandomAdd], a
ld a, [rDIV]
ld b, a
ld a, [hRandomSub]
sbc b
ld [hRandomSub], a
pop bc
ret
; 2f9f
BattleRandom:: ; 2f9f
; _BattleRandom lives in another bank.
; It handles all RNG calls in the battle engine, allowing
; link battles to remain in sync using a shared PRNG.
ld a, [hROMBank]
push af
ld a, BANK(_BattleRandom)
rst Bankswitch
call _BattleRandom
ld [$cfb6], a
pop af
rst Bankswitch
ld a, [$cfb6]
ret
; 2fb1
Function2fb1:: ; 2fb1
push bc
ld c, a
xor a
sub c
.asm_2fb5
sub c
jr nc, .asm_2fb5
add c
ld b, a
push bc
.asm_2fbb
call Random
ld a, [hRandomAdd]
ld c, a
add b
jr c, .asm_2fbb
ld a, c
pop bc
call SimpleDivide
pop bc
ret
; 2fcb
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