Clock and control fan-out

The TPCC sends control (DCI) and 40 MHz clock signals over LVDS lines. These signals are converted to CMOS on the SURF board and fanned out to a separate set of LVDS drivers for every module. The clock is unconditionally distributed to all modules. If the EZ-USB pulls down the ES (enable select) line, all modules receive DCI. If the ES line is high, DCI is only transmitted to the module that is selected using the NSEL line.