SPRUIE9D May 2017 – May 2024 DRA74P , DRA75P , DRA76P , DRA77P
For the memory access locations of the ISIF clamp, see Section 9.3.3.11, ISS ISP Memory Mapping.
Figure 9-147 shows the ISS ISP ISIF black clamp block diagram.
The clamp value is calculated based on the pixel value of the OB region of the sensor. The clamp value is calculated separately for horizontal and vertical directions to compensate the offset drift in the horizontal and vertical directions. The sum of the horizontal and vertical clamp values is subtracted from the image data, and then the additional DC offset is added (the ISIF_CLDCOFST[12:0] CLDC bit field, an S13Q0 value). This value is added whether the black clamp module is enabled or not.
The horizontal clamp is disabled through the ISIF_CLAMPCFG[2:1] CLHMD bit field.
To enable the black clamp module, set the ISIF_CLAMPCFG[0] CLEN bit to 1. The ISIF_PPLN[15:0] PPLN bit field sets the pixel per line, and the number of pixel clock periods in one line HD period equals PPLN + 1 pixel clock. The ISIF_PPLN[15:0] bit field is not used when the input is are already HD/VD.