VS6955CA datasheet(69/90 Pages) STMICROELECTRONICS

69 / 90 page

DocID028071 Rev 2

69/90

VS6955CA

Test modes

8.1.3

‘Fade to gray’ color bar mode

In the ‘fade to gray’ color bar test pattern mode, all pixel data is replaced with a color bar that

fades vertically from 100% color bars to mid gray. The ‘fade to gray’ color bar pattern is

designed to exercise more of the color space than 100% bars whilst still requiring minimal

hardware overhead. Figure 28 gives an indication of the pattern (although the pattern is

generated as Bayer data).

Figure 28. ‘Fade to gray’ color bars

The pattern is made up of eight vertical bars that fade vertically from one of the 100% color

bar colors towards a mid-gray at the bottom. The bars follow the same order as standard

color bars. Each of the bars is sub-divided vertically into a left hand side that contains a

smooth gradient and a right hand size that contains a quaintest version.

The aim of the quaintest portion is to offer areas of flat-field Bayer data that should be large

enough to result in known data values even after demosiac (independently of the demosiac

algorithm). To ensure maximum dynamic range in the quaintest data, the LSBs of the

quaintest data is generated by copying the MSBs of the unquantized data (rather than

forcing them to 0). The pattern may roll over and repeat if the frames is long enough.

8.1.4

PN9 mode

In the ‘PN9’ test pattern mode, all data on all lines between FS and LS code and the LE or

FE code is replaced with data from internally generated 511-bit pseudo-random ‘PN9’

sequence.

Figure 29. PN9 linear feedback filter

The PN9 test pattern is included to ease testing of sensor-link integrity (for example,

measurement of bit error rate). The standard PN9 linear feedback shift register with

polynomial X9+X5+1 in Fibonacci-type notation is shown in Figure 29. The PN9 sequence

0 = 1

9 + X5 + 1

VS6955CA Datasheet(PDF) 69 Page - STMicroelectronics