The histogram format as implemented in filterHisto.asm
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For both the energy histogram block, and the time histogram block, we have
Nwords = 64 channels * 3 gains * 16 bins

The histogram bin number varies first, then the gain, then the channel number.

All bins are 32-bit integers with saturation.

The bin ordering may seem weird:

bin number:	abscissa:
	0	0
	1	1
	...	...
	6	6
	7	overflow
	8	underflow
	9	-7
	...	...
	15	-1