Cirrus Logic AN269 - Manual (Page 9)

AN269
AN269REV1 9
5. GENERAL DESCRIPTION OF PIXEL OUTPUT MODES
Each display type specifies the number of bits (and therefore bits per color) clocked out per SPCLK period. The
EP93xx supports a variety of formats, as specified in the “Output Shift Mode Table” and “Color Mode Definition Ta-
ble” in the PixelMode register (refer to the Raster Engine chapter in the EP93xx User’s Guide for these tables).
Certain restrictions apply to these settings (as certain modes must be used together). These restrictions, along with
the appropriate pins, are located in the table entitled “Output Pixel Transfer Modes” (again refer to the EP93xx Ras-
ter Engine chapter).
To use the “Output Pixel Transfer Modes” table, locate the output mode that corresponds to the display that is being
used. For both monochrome and color displays, the bits with highest significance should be attached to the display.
For example, if the output mode offers bits 7, 6, and 5, but the display only allows a single bit for each color, then
bit 7 should be chosen from each color. For monochrome displays, consecutive pixels should be chosen from the
same color. This will ensure that the grayscale look-up tables function as expected, as each LUT performs opera-
tions on a single color.
Some of the more common output modes are listed in the following diagrams, detailing where the pixel outputs end
up on the display and which corresponding pins are used for each color. These diagrams are most helpful when
viewed in color. A brief description of the mode follows each diagram. The input to these diagrams would be the
most-significant bits from the color and/or grayscale LUTs and the pixel MUX. Again, for monochrome displays, a
single color output (Red, Green, or Blue) should be used to ensure proper output.
Note that these diagrams are only a graphical representation of the information from the “Output Pixel Transfer
Modes” table in the Raster Engine chapter in the EP93xx User’s Guide. Unused or redundant output pins are those
specified with gray text and a black background.