Renesas SH7781 - Manual (Page 977)

19. Display Unit (DU)
Rev.1.00 Jan. 10, 2008 Page 947 of 1658
REJ09B0261-0100
19.4.10 Display Contention
Color Palette Contention: When performing
α blending and EOR operations, if the same color
palette is selected for both planes with the input display data format at 8 bits/pixel, color palette
contention may occur. This is because contention decisions occur not in plane units, but in pixel
units.
Figure 19.6 shows contention for a case in which data for plane 1, plane 2, and plane 3 is 8
bits/pixel,
α blending is specified for plane 1 and EOR operation is specified for plane 2, and the
same color palette is selected for the three planes. (It is assumed that there are no transparent-color
pixels in plane 1, plane 2, or plane 3.)
When contention occurs,
α blending and EOR operations become invalid, and the plane with the
highest priority is displayed.
A
Plane 1 ( α blending)
Plane 2 (EOR operation)
Plane 3
Legend:
P1: Plane 1
P2: Plane 2
P3: Plane 3
No contention
P1 is displayed
P1 and P2
contention
P1 is displayed P1, P2, and P3
contention
P1 is displayed P2 and P3
contention
P2 is displayed No contention
P3 is displayed
Note: Bold black lines indicate the display area.
Figure 19.6 Color Palette Contention
(When Same Color Palette Is Selected for Multiple Planes)
Figure 19.7 summarizes the display results when combining color palette selection and transparent
colors in the display section A in Figure 19.6.
• P1αP2 shows the result of α blending of plane 1 and plane 2.
• P2⊕P3 shows the result of an EOR operation on plane 2 and plane 3.
• P1α (P2⊕P3) shows the result of α blending of plane 1 with the result of an EOR operation on
plane 2 and Plane 3.
• BPOR shows display data in the background color register.