static void lcd_tick(void)
{
    unsigned data;

    if (lcd_state != LCD_NEED_UPDATE)
        return;
        
    data = bcm_read32(0x1F8);
    if (data == 0xFFFA0005 || data == 0xFFFF) /* Not ready for update - return */
        return;
    
    /* kick off update and reset request */
    bcm_write32(0x1F8, 0xFFFA0005);
    BCM_CONTROL = 0x31;
    lcd_state = LCD_IDLE;
}