GameBoy\Opcode::opcode61 PHP Method

    public static function opcode61(Core $core)
    {
        $core->registerA = $core->unsbtub($core->registerA - 1);
        $core->FZero = $core->registerA == 0;
        $core->FHalfCarry = ($core->registerA & 0xf) == 0xf;
        $core->FSubtract = true;
    }