CHAN_B
c = (ch->ch_nr == 1) ? CHAN_A : CHAN_B;
bes = scc_getmreg(bas, CHAN_B, CR_RSTXSI);
src = scc_getmreg(bas, CHAN_B, RR_SRC);
.cl_range = (CHAN_B - 16),
.cl_range = (CHAN_B - 2),