SB_BUSY
ret = wait_for((REG_READ(SB_PCKT) & SB_BUSY) == 0, 1000);
ret = wait_for((REG_READ(SB_PCKT) & SB_BUSY) == 0, 1000);
ret = wait_for((REG_READ(SB_PCKT) & SB_BUSY) == 0, 1000);
ret = wait_for((REG_READ(SB_PCKT) & SB_BUSY) == 0, 1000);