swim3_select
swim3_select(fs, RELAX);
swim3_select(fs, RELAX);
swim3_select(fs, RELAX);
swim3_select(fs, action);
swim3_select(fs, bit);
swim3_select(fs, READ_DATA_0);
swim3_select(fs, STEP);
swim3_select(fs, fs->head? READ_DATA_1: READ_DATA_0);
swim3_select(fs, RELAX);
swim3_select(fs, RELAX);
swim3_select(fs, RELAX);
swim3_select(fs, RELAX);
swim3_select(fs, RELAX);