STM_CTRL_BITBUF_PTR_CLR
desc->stm_ctrl |= STM_CTRL_BITBUF_PTR_CLR(1);
cfg_desc->stm_ctrl |= STM_CTRL_BITBUF_PTR_CLR(1);
cfg_desc->stm_ctrl |= STM_CTRL_BITBUF_PTR_CLR(1);
desc->stm_ctrl |= STM_CTRL_BITBUF_PTR_CLR(1);