CS5530 datasheet(132/241 Pages) NSC

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Revision 4.1

Functional Description (Continued)

3.8.3

Video Overlay

The video data from the color-space converter is then

mixed with the graphics data based upon the video win-

dow position. The video window position is programmable

via the Video X and Y Position Registers (F4BAR+Mem-

ory Offset 08h and 0Ch). A color-keying mechanism is

employed to compare either the source (video) or destina-

tion (graphics) color to the color key programmed via the

Video Color Key Register (FBAR+Offset 14h) and to

select the appropriate pixel for display within the video

window. The range of the color key is programmable by

setting the appropriate bits in the Video Color Mask Reg-

ister (F4BAR+Memory Offset 18h). This mechanism

greatly reduces the software overhead for computing visi-

ble pixels, and ensures that the video display window may

be partially occluded by overlapping graphics data.

Tables 3-73 and 3-74 show the bit formats for these regis-

ters

The CS5530 accepts graphics data over the PIXEL[23:0]

interface from the GXLV processor at the screen DOT

clock rate. The CS5530 is capable of displaying graphics

resolutions up to 1600x1200 at color depths up to 24 bits

per pixel (bpp) while simultaneously overlaying a video

window.

Table 3-73. Video X and Y Position Registers

Bit

Description

F4BAR+Memory Offset 08h-0Bh

Video X Register (R/W)

Reset Value = xxxxxxxxh

31:27

Reserved: Set to 0.

26:16

VideoXEndPosition: This field represents the horizontal end position of the video window according to the following

formula: Position programmed = screen position + (H_TOTAL – H_SYNC_END) – 13.

15:11

Reserved: Set to 0.

10:0

Video X Start Position: This field represents the horizontal start position of the video window according to the following

formula: Position programmed = screen position + (H_TOTAL – H_SYNC_END) – 13.

F4BAR+Memory Offset 0Ch-0Fh

Video Y Register (R/W)

Reset Value = xxxxxxxxh

31:27

Reserved: Set to 0.

26:16

VideoYEndPosition: This field represents the vertical end position of the video window according to the following for-

mula: Position programmed = screen position + (V_TOTAL – V_SYNC_END) + 1.

15:11

Reserved: Set to 0.

10:0

Video Y Start Position: This field represents the vertical start position of the video window according to the following for-

mula: Position programmed = screen position + (V_TOTAL – V_SYNC_END) + 1.

Table 3-74. Video Color Registers

Bit

Description

F4BAR+Memory Offset 14h-17h

Video Color Key Register (R/W)

Reset Value = xxxxxxxxh

31:24

Reserved: Set to 0.

23:0

Video Color Key: This field represents the video color key. It is a 24-bit RGB value. The graphics or video data being

compared may be masked prior to the compare by programming the Video Color Mask register appropriately.

F4BAR+Memory Offset 18h-1Bh

Video Color Mask Register (R/W)

Reset Value = xxxxxxxxh

31:24

Reserved: Set to 0.

23:0

Video Color Mask: This field represents the video color mask. It is a 24-bit RGB value. Zeroes in the mask cause the

corresponding bits in the graphics or video stream being compared to be ignored.

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