52.6.16 Histogram Module
For each possible pixel value, the histogram counts the number of times the value was encountered in the current image. RGGB Bayer, raw data or luminance histogram are available. There are 512 entries in the histogram entries, and each histogram bin can count up to 220 data. As the table entries are limited, each bin is actually a range, i.e., least significant bits are ignored. A write to ISC_CTRLEN.HISREQ initiates a new histogram. The counting operation ends when ISC_INTSR.HISDONE is set. At that time, a software or hardware DMA transfer copies the table from the interface to the internal or external memory. To clear the table content (for a new operation), use ISC_CTRLEN.HISCLR. An automatic clear (reset after read) is available when ISC_HIS_CFG.RAR is set. In that case, as soon as the data is read from the table, the table entry is cleared.
