write_tcvr_bit
write_tcvr_bit(bp, tregs, ((byte >> shift) & 1));
write_tcvr_bit(bp, tregs, 0);
write_tcvr_bit(bp, tregs, 1);
write_tcvr_bit(bp, tregs, 0);
write_tcvr_bit(bp, tregs, 1);
write_tcvr_bit(bp, tregs, 1);
write_tcvr_bit(bp, tregs, 0);
write_tcvr_bit(bp, tregs, (val >> shift) & 1);
write_tcvr_bit(bp, tregs, 0);
write_tcvr_bit(bp, tregs, 1);
write_tcvr_bit(bp, tregs, 1);
write_tcvr_bit(bp, tregs, 0);