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Intel® PXA255 Processor Developer’s Manual 7-7
LCD Controller
Either of two matrices may be used for each color, chosen by bits 0, 1, and 14 of the TMED
Control Register (TCR, Section 7.6.10). Offsets may be selected for the shading of each color to
avoid gray color problems. Although these offset values are panel dependent, the recommended
values are listed in Section 7.6.9, with the blue data path being used for monochrome modes.
Offsets may also be chosen in the TMED Control Register for shifting the row (horizontal) value,
line (vertical) value, and frame number.
Figure 7-4 shows the block diagram for TMED. Pixel data (up to 8 bits) enters the module and is
sent through the Color Value (CV) generator. Depending on the value of the TCR[TSCS] field, the
CV generator rounds off between 0 and 3 of the least-significant bits, creating a new CV. If the
original pixel value is 254 or 255, the final data output is set to one. Otherwise, the following
occurs:
1. The new CV is sent through the Color Offset Adjuster, where it is used as a lookup into the
matrix selected by TCR[COAM].
2. Either the 8-bit output of the chosen matrix or 00h, as selected by TCR[COAE], is added to the
appropriate color’s seed register value in register TRGBR to form an offset.
3. This offset is added to the result of the multiplication of the Frame Number and the CV to form
the algorithm’s lower boundary (only the lower 8 bits are used).
4. The CV is added to the lower boundary to obtain the upper boundary.
5. Row (line) and column (pixel) counters are combined with beat suppression (offset) values in
the Pixel Number Adjuster and Address Generator to form yet another address for a matrix
lookup.
6. The output of the chosen matrix is compared to the lower and upper boundaries in the Data
Generator.
7. If the matrix output is between these boundaries or the original pixel value is 254 or 255, then
the data output to the panel is one. In all other cases, it is zero.
Figure 7-3. Compare Range for TMED
0255
128
192
64
Compare
Range
(LB+PV) mod 256
LB=(PixelValue * Frame#) mod 256 + Offset