SSC_CTL_SR
st_i2c_set_bits(i2c_dev->base + SSC_CTL, SSC_CTL_SR);
st_i2c_clr_bits(i2c_dev->base + SSC_CTL, SSC_CTL_SR);
var |= SSC_CTL_SR;
var &= ~SSC_CTL_SR;