An269 – Cirrus Logic AN269 User Manual
Page 47
AN269
AN269REV1
47
The interpretation of this diagram is simple. For the first video frame, if the color Red[7:5] = 001b covers the
entire screen, then the red pixel output will be as shown in the following table (where x,y = 0,0 is the top left
of the screen):
As can be seen from the diagram above, the patterns repeat based on horizontal and vertical positions. The
same will occur during frames 1, 2, and 3.
Since each pixel is on 25% of the total time, this entry in the grayscale table will produce 25% brightness on
the red channel. Note again that the actual pixel output from the grayscale generator is only 1 pixel, but the
value of that pixel depends on the horizontal position, vertical position, and frame number.
Frame 0
HCNT
=00b
HCNT
=01b
HCNT
=10b
HCNT
=11b
Frame 1
HCNT
=00b
HCNT
=01b
HCNT
=10b
HCNT
=11b
VCNT=00b
0
1
0
0
0
0
0
1
VCNT=01b
0
0
1
0
1
0
0
0
VCNT=10b
0
0
0
1
0
1
0
0
VCNT=11b
1
0
0
0
0
0
1
0
Frame 2
HCNT
=00b
HCNT
=01b
HCNT
=10b
HCNT
=11b
Frame 3
HCNT
=00b
HCNT
=01b
HCNT
=10b
HCNT
=11b
VCNT=00b
0
0
1
0
1
0
0
0
VCNT=01b
0
1
0
0
0
0
0
1
VCNT=10b
1
0
0
0
0
0
1
0
VCNT=11b
0
0
0
1
0
1
0
0
Table 8. Grayscale Output for Red[7:5] = 001b
x,y
x=0
x=1
x=2
x=3
x=4
x=5
x=6
x=7
etc.
y=0
0
1
0
0
0
0
0
1
y=1
0
0
1
0
1
0
0
0
y=2
0
0
0
1
0
1
0
0
y=3
1
0
0
0
0
0
1
0
y=4
0
1
0
0
0
1
0
0
y=5
0
0
1
0
0
0
1
0
y=6
0
0
0
1
0
0
0
1
y=7
1
0
0
0
1
0
0
0
etc.
Table 9. Grayscale Output for Red[7:5] = 001b, First Video Frame