CR_BCN_INTERVAL
{ CR_ATIM_WND_PERIOD, CR_PRE_TBTT, CR_BCN_INTERVAL };
reqs[2].addr = CR_BCN_INTERVAL;
r = zd_iowrite32_locked(chip, b_interval, CR_BCN_INTERVAL);
return zd_ioread32(chip, CR_BCN_INTERVAL, interval);