Destlinelength – Cirrus Logic EP93xx User Manual
Page 293
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Copyright 2007 Cirrus Logic
Graphics Accelerator
EP93xx User’s Guide
8
8
8
DESTLINELENGTH
Address:
0x8004_0020 - Read/Write
Default:
0x0000_0000
Mask:
0x0000_0FFF
Definition:
Block Destination Line Length Register
Bit Descriptions:
RSVD:
Reserved - Unknown during read
LEN:
Length - Read/Write
The value in this field specifies the number of 32 bit words,
minus 1, that are needed to contain all of the pixels that
comprise width of the display. The value of LEN is
determined by:
1) Find how many pixels occupy a 32-bit word. For
example, four 8-bit pixels can occupy a 32-bit word.
2) Find the width of the display in pixels. For example, a
640x480 display has a width of 640 pixels.
3) The line length, LEN, is determined by the stride of the
display, that is, how many 32-bit words are needed to
populate the width of the display with pixels. From steps 1
and 2, the stride for this example is 640 pixels divided by
4, where 4 is the number of 8-bit pixels that occupy a
word. So, for this example, LEN = 640 / 4 = 160 = 0xA0.
Usually the same LEN value is used in both the
register and the
register.
31
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20
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RSVD
15
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4
3
2
1
0
RSVD
LEN