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; The CGB hardware introduces Double Speed Mode.
; While active, the clock speed is doubled.
; The hardware can switch between normal speed
; and double speed at any time, but LCD output
; collapses during the switch.
DoubleSpeed::
ld hl, rKEY1
bit 7, [hl]
jr z, SwitchSpeed
ret
NormalSpeed::
ld hl, rKEY1
bit 7, [hl]
ret z
SwitchSpeed::
set 0, [hl]
xor a
ldh [rIF], a
ldh [rIE], a
ld a, $30
ldh [rJOYP], a
stop ; rgbasm adds a nop after this instruction by default
ret
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