FERA branch management

The FVI is a D size VXI module. the front panel supplies the FERA commands and data, the NIM I/O and somes probes and flags as descibed in the nexts sections. The size does not allows more than two FERA branches per module but it will be possible to connect together several modules, that is to control more than 2 FERA branches. There is no FVI "Master" or "Slave", each module is identical but the ancillary trigger must:

1. handshake with only ONE FVI.
2. receive INHIBIT from every FVI
3. wait FERA coding and FERA readout completion from every FVI before restart its own logic.