A spike splitter.
Indexed spikes coming in on the left are dietributed to the four output ports on the right according to their index. Spikes with index above 3 (Catacomb indices always start from 0) are discarded.
The multi-channel output port at the top is a special case for connecting the splitter to a population of spike receivers via a SpikeProjection. It makes the spike splitter behave as though it were a population itself, with nOutput elements. A incoming spike of index _tt(n) is causes the _tt(n)'th virtual cell to send a spike of index 0.
Thus, for example, the splitter can be connected with all-all connectivity to a population of cells. For an input spike of index n, every cell in the target population will receive a spike, as if coming from the n'th cell in a population. Each target cell will therefore have nOutput different synapses.
This can be compared with what would happen if you bypass the spike-splitter and just connect a normal spike cable to the population. In that case, a spike of index n will be sent only to the n'th cell, with its index reset to 0.
WARNING connecting an ordinary spike cable to the multi-channel output will generate an error indicating that the system does not know what to do.