CL-PS7500FE
System-on-a-Chip for Internet Appliance
12.2 Palette
The CL-PS7500FE has a 28-bit-wide, 256-entry palette constructed out of three 8-bit-wide LUTs, each
has 256 entries, named Red, Green, and Blue and one 4-bit-wide LUT with 16 entries, named Ext. The
Red, Green, and Blue LUTs each drive their respective DACs.The Ext LUT is normally configured to drive
the ED[3:0] output port, except when HiRes mode or LCD mode is selected.These bits may be used out-
side the chip for a variety of purposes such as supremacy, fading, HiRes, and LCD driving. The ED[7:4]
output port is normally driven from the External register – EREG[7:4] – that can be written at any time.
These bits can be used as a DC control port.
The mapping of the logical colors through the LUTs is dependent on the mode in use, as follows:
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In 1-, 2-, 4-bits/pixel modes, the logical data is fed simultaneously to all four LUTs. This allows a completely
flexible palette with any logical color mapped to any physical color and any ED[3:0] value. The palette gives
16 colors from a selection of 2 .
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In 8-bits/pixel modes, the logical data is fed simultaneously to all 4 LUTs. This allows a completely flexible
palette with any logical color being mapped to any physical color. Logical colors 0–15 access the Next LUT;
logical colors 16–255 access location 0 of the Ext LUT. The Ext LUT again drives ED[3:0]. The palette gives
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256 colors from a selection of 2 .
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In 16-bpp mode, a patented technique has been developed.This approach is highly flexible and allows many
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different addressing modes (for example, 5:5:5, 5:6:5, and so on). In this mode, 2 colors are available from
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a selection of 2 .
In 32-bpp mode, 24 bits from the logical field drive the 256 entries in each of the color LUTs (8 bits to each
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LUT); 4 bits drive the Ext LUT; the upper 4 bits are discarded.The palette gives the full range of 2 colors.
NOTE: Where a logical field does not drive all the palette entries (for example, in 4-bpp mode), only the lower por-
tion of the palette is used. Unused sections need not be programmed.
When HiRes or LCD mode is selected, the palette must be set up in a predetermined configuration. This
is explained in Section 12.4 and Section 12.5.
12.2.1 Palette Updating
The FLYBK signal is an output in the CL-PS7500FE from the video and sound macrocell. FLYBK goes
high at the start of the first raster that is not displayed, and goes low at the start of the first raster that is
displayed.The rising edge of this signal can cause an interrupt through the CL-PS7500FE IRQA interrupt
registers and the palette is updated at this time for flicker-free updating.
12.3 Cursor
The CL-PS7500FE has a hardware cursor 32-pixels wide and N pixels high. The 2-bpp allow four colors,
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including ‘transparent’, plus three other colors from a selection of 2 .The cursor is displayable in the hor-
izontal border, but not in the vertical border.
The cursor is a 28-bit-wide, three-entry palette, allowing each cursor logical color to be any physical color.
There is also a 28-bit-wide border color register.
At the start of every frame, 16 bytes of cursor data transfer to the video subsystem during the horizontal
retrace period. This is enough data for two rasters worth of cursor. After they are displayed, a request is
made for another 16 bytes. In Normal mode, requests are made on every other raster where there is a
cursor and enough data transfers for two rasters each. In HiRes mode, a request is made every raster.
NOTE: The cursor data always transfers in 4-word bursts.
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June 1997
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